Application Finder

Portable Raman is used to quantify trigonelline, an alkaloid that contributes to the health benefits of some foods. A simple method to quantify the presence of diluted trigonelline in solutions using surface enhanced Raman spectroscopy is described. Portable Raman is a tool that could be used in quality control of food items such as coffee and quinoa.

Edible oils are not only a major source of nutrition but also a key basic material in the food industry. Vegetable oils are increasingly important because of their high content in mono- and polyunsaturated fatty acids in comparison with animal fats. In this application note, the main ingredients of olive oil, camellia oil, arachis oil, sunflower seed oil, and colza oil are analyzed using a portable Raman spectrometer combined with chemometrics software.

Today’s Raman instrumentation is faster, more rugged, and less expensive than previous instrumentation.The design of high performance, portable and handheld devices has introduced the technology to new application areas that were previously not possible with older, more cumbersome instruments. Handheld Raman instruments such as the NanoRam® from B&W Tek are well-suited for pharmaceutical applications such as the testing of raw materials, verification of final products and the identification of counterfeit drugs due to the technique’s extremely high molecular selectivity.

Ternary mixtures of aqueous sugar solutions are measured and multivariate models of the concentration of analytes developed using BWIQ software.

Cellulose is a common naturally-derived raw excipient found in the majority of pharmaceutical products. Raw material testing is required to ensure that consumers are receiving quality cellulose and its derivatives. The NanoRam®-1064 is an asset for pharmaceutical identity testing, minimizing fluorescence generated by typical handheld Raman systems with 785 nm lasers. As such, the NanoRam®-1064 is used here to identify cellulose derivatives that would normally fluoresce with a 785 nm laser.

The TacticID®-GP Plus has multiple measurement modes to support safety and security users. A-Mode allows the user to create library Raman or SERS spectra customizable for spectral search range and hit quality index (HQI) threshold. A-mode is of beneficial use to forensics laboratories that would like to utilize expansion of SERS detection of designer drugs specific to their geographical regions or for food safety in perspective markets. In this example, A-Mode is used to create a SERS library of melamine to easily detect the presence of melamine in infant formula using a single indicator peak.

Research laboratories must expand their capabilities to routinely analyze candidate microplastics from environmental samples to determine their origin and help predict biological impacts. Spectroscopic techniques are well suited to polymer identification. Laboratory Raman spectroscopy is an alternative to confocal Raman microscopes and Fourier transform infrared (FTIR) microscopes for quick identification of polymer materials. Raman microscopy was used to identify very small microplastic particles in this Application Note.

Although the process of building, validating and using a method is well-defined through software, the robustness of the method is dependent on proper practice of sampling, validation, and method maintenance. In this document, we will detail the recommended practices for using the multivariate method with NanoRam-1064. These practices are recommended for end users who are in the pharmaceutical environment, and can expand to other industries as well. This document aims to serve as a general reference for NanoRam-1064 users who would like to build an SOP for method development, validation and implementation.

Raman spectroscopy’s use for process analytics in the pharmaceutical and chemical industries continues to grow due to its nondestructive measurements, fast analysis times, and ability to do both qualitative and quantitative analysis. Spectral preprocessing algorithms are routinely applied to quantitative spectroscopic data in order to enhance spectral features while minimizing variability unrelated to the analyte in question. In this technical note we discuss the main preprocessing options pertinent to Raman spectroscopy with real applications examples, and to review the algorithms available in B&W Tek and Metrohm software so that the reader becomes comfortable applying them to build Raman quantitative models.

The coupling of highly efficient ion chromatography (IC) to multi-dimensional detectors such as a mass spectrometer (MS) or an inductively coupled plasma mass spectrometer (ICP/MS) significantly increases sensitivity while simultaneously reducing possible matrix interference to the absolute minimum. By means of IC/MS several oxyhalides such as bromate and perchlorate can be detected in the sub-ppb range. Additionally, organic acids can be precisely quantified through mass-based determination even in the presence of high salt matrices. By means of IC-ICP/MS different valence states of the potentially hazardous chromium, arsenic and selenium in the form of inorganic and organic species can be sensitively and unambiguously identified in one single run.

A complete tap water analysis includes the determination of the pH value, the alkalinity and the total water hardness. Both the pH measurement and the pH titration by means of a standard pH electrode suffer from several drawbacks. First, the response time of several minutes is too long and, above all, the stirring rate significantly influences the measured pH value. Unlike these standard pH electrodes, the Aquatrode Plus with its special glass membrane guarantees rapid, correct and very precise pH measurements and pH titrations in solutions that have a low ionic strength or are weakly buffered. Total water hardness is ideally determined by a calcium ion-selective electrode (Ca ISE). In a complexometric titration, calcium and magnesium can be simultaneously determined up to a calcium/magnesium ratio of 10:1. Detection limits for both ions are in the range of 0.01 mmol/L.

A convenient adsorptive cathodic stripping voltammetric (AdCSV) method has been developed for trace determination of uranium(VI) in drinking water samples using chloranilic acid (CAA). The presence of various matrix components (KNO3, Cl-, Cu2+, organics) can impair the determination of the uranium-CAA complex. The interferences can be mitigated, however, by appropriate selection of the voltammetric parameters. While problematic water samples still allow uranium determination in the lower µg/L range, in slightly polluted tap water samples uranium can be determined down to the ng/L range, comparable to the determination by current ICP-MS methods.

For a variety of reasons, the water content of chocolate is of crucial importance and has to be accurately determined. This poster compares an automated version of the Karl Fischer titration (KFT) using the sequential addition of various solvents with the widespread manual titration at elevated temperatures using a chloroform/methanol mixture. The water contents determined by the two procedures show excellent agreement. However, manual titration requires laborintensive sample preparation, the side reactions are difficult to quantify and hazardous halogenated solvents have to be used. In contrast, automated KFT is straightforward, uses non-hazardous solvents, allows to quantify the side reactions and is easily applicable to water determinations in sugar- and fat-containing matrices.

The analytical challenge treated in the present work consists in the determination of chloride, phosphate and sulfate in the presence of difficult sample matrices that interact with the stationary column phase or even render it unusable. Metrohm`s patented stopped-flow dialysis coupled to the new 881 Compact IC pro ion chromatograph overcomes these drawbacks. Two standard solutions covering the concentration ranges 1.0…3.6 mg/L and 10…36 mg/L as well as two samples, an ultra-high temperature (UHT) processed milk and a baby milk powder, were characterized in terms of analyte concentration, relative standard deviation, calibration quality, carryover and recovery rates. While the five-point calibration curves yielded correlation coefficients (R) better than 0.9999, carryover (between two subsequent injections of a concentrated sample and a blank) was less than 0.49%. Recoveries for the low (10…36 mg/L) and high standard concentrations (1.0…3.6 mg/L) were within 91…99% and 94…100%, respectively. Automated compact stopped-flow dialysis is a leading-edge sample preparation technique that ensures optimum separation performance by effectively protecting the column from detrimental matrix compounds.

This poster describes a simple and sensitive method for the determination of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in water samples by suppressed conductivity detection. Separation was achieved by isocratic elution on a reversed-phase column thermostated at 35 °C using an aqueous mobile phase containing boric acid and acetonitrile. The PFOA and PFOS content in the water matrix was quantified by direct injection applying a 1000 μL loop. For the concentration range of 2 to 50 μg/mL and 10 to 250 μg/mL, the linear calibration curve for PFOA and PFOS yielded correlation coefficients (R) of 0.99990 and 0.9991, respectively. The relative standard deviations were smaller than 5.8%.The presence of high concentrations of mono and divalent anions such as chloride and sulfate has no significant influence on the determination of the perfluorinated alkyl substances (PFAS). In contrast, the presence of divalent cations, such as calcium and magnesium, which are normally present in water matrices, impairs PFOS recovery. This drawback was overcome by applying Metrohm`s Inline Cation Removal. While the interfering divalent cations are exchanged for non-interfering sodium cations, PFOA and PFOS are directly transferred to the sample loop. After inline cation removal, PFAS recovery in water samples containing 350 mg/mL of Ca2+ and Mg2+ improved from 90…115% to 93…107%.While PFAS determination of low salt-containing water samples is best performed by straightforward direct-injection IC, water rich in alkaline-earth metals are best analyzed using Metrohm`s Inline Cation Removal.

Psychoactive gamma-hydroxybutyrate (GHB) and its prodrug gamma-butyrolactone (GBL) are substances that are increasingly abused as date-rape and recreational (party) drugs. Since the non-controlled GBL converts into the illicit GHB both in-vivo and in-vitro, their legal distinction is of crucial importance.For the forensic determination of illegally added GHB and GBL in commonly consumed beverages, this work presents a simple and sensitive method that employs direct-injection ion chromatography combined with spectrophotometric detection. The method allows to trace GHB-GLB interconversion, whether in vivo or in vitro lactone cleavage or intramolecular GHB esterification, and thus complies with pertinent requirements of law enforcement agencies.

UV/VIS detection is one of the most sensitive detection techniques in trace-level chromatography. Sometimes, however, spectrophotometric detection lacks sensitivity, selectivity or reproducibility and chemical derivatizations are required. By using Metrohm`s rugged and versatile flow-through reactor, single- or multi-step derivatizations can be done fully automatically, in either pre- or post-column mode at any temperature between 25…120 °C. The variable reactor geometry allows to adjust the reactor residence time of the reactants according to derivatization kinetics. The flexibility of the reactor is demonstrated by optimizing four widespread post-column techniques: the relatively slow ninhydrin reaction with amino acids and the fast derivatizations of silicate, bromate and chromate(VI).

The Rancimat method is a widely accepted method for the determination of the oxidation stability of natural fats and oils. Its main application is quality control in oil mills and the oil processing industry. At elevated temperatures and under the exposure of air, fatty acids are oxidized. The reaction products are absorbed in ultrapure water that is continually monitored for conductivity. After an induction period with slow reaction, the formation of volatile carboxylic acids is accelerated. At that time the conductivity begins to increase rapidly. Instead of investing weeks or months, the sample can be oxidized within a few hours.The method can also be used to determine the oxidation stability of solid foodstuffs that contain natural fats or oils. Frequently, a direct determination without extraction of the fat is possible, if the fat content exceeds a minimum level. In these cases, a simple and reliable assessment of the quality of the produced foodstuff is possible.A number of fat-containing solid foodstuffs such as almonds, peanuts, peanut-flavored puffs, potato chips, muffins, butter cookies, French fries, and instant noodles were successfully tested with the Rancimat method. The experiments revealed that the comminution of the sample is one of the most important steps. The grinding procedure of the tested samples was kept as simple as possible to avoid the use of expensive milling instrumentation.

This poster discusses results showing the influence of pH, temperature of the post-column reactor, eluent composition, and iodide concentration on the sensitivity of the triiodide method.

The poster describes the development of an automated Karl Fischer method for determining the water content in different edible oils.

Thermometric titration can solve application problems that potentiometry cannot solve at all, or at least not satisfactorily.

This poster looks at the possibility to modify the existing EPA Method to meet California's rigorous public health goal (PHG) of 0.02 µg/L. After optimizing instrument settings and method parameters, a method detection limit (MDL) of 0.01 µg/L is obtained.

Non-enzymatic ethanol sensor based on a nanostructured disposable screen-printed electrode.

Ion chromatography tackles difficult separation problems of various ionic species and typically works with conductivity detection. Mass detection as a secondary independent detector significantly lowers the detection limits and confirms the identity of analytes even when coeluting. This poster describes how the combination of IC-MS and automated sample preparation techniques cope with the analysis of anions and oxoanions in challenging matrices such as soil or explosion residues.

This poster demonstrates the feasibility of coupling a Metrohm IC system to a PerkinElmer NexION ICP-MS, operated under Empower 3 Software.Using a Metrosep Carb 2 column, the chromatographic separation of both species was achieved with a high resolution. Low background and high sensitivity allow determination in the low ng/L range.Optimal separation and full complexation of Cr(III) is already possible with EDTA concentrations from 40 μmol/L in low matrix solutions and may need to be increased depending on the sample matrix.Handling of the system was easy and user friendly. It was shown that speciation of Cr(III) and Cr(VI) can be carried out on this system utilizing a professional data system for acquisition, processing, and reporting.

Moisture in cannabis impacts potency and must be accurately determined. Loss on drying (LOD) is the most popular method for determining moisture in cannabis. Unfortunately, this technique is not specific to moisture and the loss of any volatile components, such as terpenes, will be incorrectly classified as moisture. Karl Fischer (KF) titration is the only chemically specific test for moisture. This poster describes the instrument used to determine moisture content by Karl Fischer titration and compares the results of this data to loss on drying.

LC-MS/MS quantification methods are commonly used to determine trace levels of organic compounds. However, highly polar reversed phases (RPs) lack sufficient retention for very polar compounds, or they fail for charged organics. Separation using ion chromatography (IC) and subsequent MS/MS detection is an innovative alternative approach that combines the fast elution and flexibility of the IC system with the excellent resolution and high sensitivity of the MS/MS detector. This poster presents a fast, robust and reliable IC-MS/MS method for the detection of HAAs and other ionic analytes using the high-end MS/MS system QTRAP 6500+ from SCIEX coupled to a the 940 Professional IC Vario One SeS/PP/HPG instrument. This analytical setup is able to identify and quantify the presence of HAAs at trace levels with LLODs between 0.02 μg/mL and 0.2 μg/L on a single HAA. This capability easily fulfills the sensitivity requirements specified in EU Drinking Water Directive, which specifies a maximum residue level (MRL) of 60 mg/mL for the sum of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid present in the representative sample.

Lead is known to be highly toxic, and lead salts are easily resorbed by humans. Cases of chronic lead poisoning caused by lead metal used in the water piping system are well known. Therefore, the control of drinking water for lead content is of utmost importance. The Lead and Copper Rule (LCR) published by the USEPA (United States Environmental Protection Agency) states an action limit of 15 μg/L lead for drinking water. Using a portable voltammetric instrument, lead can be determined in these concentrations directly at the point of sampling.

In the following tables, the half-wave potentials or peak potentials of 90 metal ions are listed. The half-wave potentials (listed in volts) are measured at the dropping mercury electrode (DME) at 25 °C unless indicated otherwise.

The potentiometric titration of Kjeldahl nitrogen is one of the most common analytic procedures. It is referenced in numerous standards, ranging from the food and animal feed industries through sewage and waste analysis and all the way to the fertilizer industry. As a rule, the samples are digested with concentrated sulfuric acid with the addition of a catalyst. The ammonium sulfate that is formed is distilled as ammonia in alkali solution, collected in an absorption solution and titrated there.This Bulletin provides a detailed description of potentiometric nitrogen determination following distillation of the digestion solution, followed by a discussion of the possibilities of coulometric titration (without distillation).

The quantitative determination of the alkaloid nicotine, which is an essential constituent of the tobacco plant, can be carried out by polarography. The quantification limit is less than 0.1 mg/L in the polarographic vessel.

Fructose (fruit sugar) is the only ketose that occurs naturally. It is found free in a mixture with dextrose (honey, sweet fruits, tomatoes) or bound as a component of cane sugar and various starch-like carbohydrates. As fructose tastes sweeter than dextrose, it finds great use as a sweetening agent.In 1932, the polarographic reducibility of sugar was described for the first time by Heyrovsky and Smoler. The following method can be used to determine the fructose content of fruit, fruit juice and honey quantitatively.

The quality of egg-based pasta is primarily determined by its egg content. Also of importance, however, is the water content, which influences the storage life of the product, as well as the degree of acidity which, in the case of high values, indicates undesirable acidification during processing or drying. A check of the chloride content shows whether salt has been added to the pasta.

The photometric determination of nitrate is limited by the fact that the respective methods (salicylic acid, brucine, 2,6-dimethyl phenol, Nesslers reagent after reduction of nitrate to ammonium) are subject to interferences. The direct potentiometric determination using an ion-selective nitrate electrode causes problems in the presence of fairly large amounts of chloride or organic compounds with carboxyl groups. The polarographic method, on the other hand, is not only more rapid, but also practically insensitive to chemical interference, thus ensuring more accurate results. The limit of quantification depends on the matrix of the sample and is approximately 1 mg/L.

This Application Bulletin describes the voltammetric determination of the elements antimony, bismuth, and copper. The limit of detection for the three elements is 0.5 ... 1 µg/L.

This Application Bulletin gives an overview of the volumetric water content determination according to Karl Fischer. Amongst others, it describes the handling of electrodes, samples, and water standards. The described procedures and parameters comply with the ASTM E203.

This Bulletin describes fluoride determination in various matrices with the help of the ion-selective fluoride electrode (F-ISE). The F-ISE is comprised of a lanthanum fluoride crystal and exhibits a response in accordance with the Nernst equation across a wide range of fluoride concentrations.The first part of this Bulletin contains notes regarding the handling and care of the electrode and the actual fluoride determination itself. The second part demonstrates the direct determination of fluoride with the standard addition technique in table salt, toothpaste and mouthwash.

This document explains how to measure Na ion concentration in diverse matrices with a sodium ion-selective electrode (Na-ISE) using direct measurement and standard addition.

The quality of a vinegar depends on various factors. Since the contents of the individual components vary widely even from bottle to bottle, it is impossible to give average values. This Bulletin describes the determination of the following parameters in vinegar: pH value, total titratable acid, volatile, and non-volatile acid, free mineral acid as well as free and total sulfurous acid.

This Bulletin describes analysis methods for determining the following parameters: pH value, total titratable acid, ash alkalinity, formol number, total sulfurous acid, chloride, sulfate, calcium, and magnesium. These methods are suitable for the analysis of jams, fruit and vegetable juices, and their concentrates.

This Bulletin describes methods for measuring the pH value of dairy products. Particular attention has been paid to the handling, maintenance, and storage of the pH electrodes.

This Bulletin describes potentiometric titration methods for the determination of the acidity in milk and yoghurt according to DIN 10316, ISO/TS 11869, IDF/RM 150, ISO 6091 and IDF 86, the chloride content in milk, butter and cheese according to EN ISO 5943, IDF 88, ISO 15648, IDF 179, ISO 21422, and IDF 242. Additionally the determination of the sodium content in milk using the thermometric titration is described. The determination of the oxidation stability of butter in accordance to AOCS Cd 12b-92, ISO 6886 and GB/T 21121 as well as the determination of lactose in lactose free milk by ion chromatography is also described.For the determination of the pH value in dairy products see Application Bulletin AB-086 and for the determination of calcium and magnesium see Application Bulletin AB-235.

This Application Bulletin describes the determination of mercury by anodic stripping voltammetry (ASV) at the rotating gold electrode. With a deposition time of 90 s, the calibration curve is linear from 0.4 to 15 μg/L; the limit of quantification is 0.4 μg/L.The method has primarily been drawn up for investigating water samples. After appropriate digestion, the determination of mercury is possible even in samples with a high load of organic substances (wastewater, food and semi-luxuries, biological fluids, pharmaceuticals).

Edible oils and fats contain natural tocopherols and, in some cases, also synthetic tocopherols added as antioxidants. The method described below allows the simple and rapid determination of the tocopherol content by voltammetry. The tocopherols are oxidized electrochemically at the glassy carbon electrode (GCE). The limit of quantitation is approximately 5 ppm (mg/kg) tocopherol.

In addition to its natural occurrence in fruit and vegetables, ascorbic acid (Vitamin C) is used as an antioxidant in foods and drinks. Ascorbic acid is furthermore also to be found in numerous drugs.Ascorbic acid and its salts and esters can be determined with titration or by using polarography, for which ascorbic acid is oxidized to form dehydroascorbic acid.Bi-voltammetric or photometric equivalence point indication can be used for titrimetric determination. It must be taken into account here that only bi-voltammetric indication is independent of the inherent color of the sample. Polarography is the most selective of the methods described, as other reducing or oxidizing substances are not recorded.

This bulletin contains two parts. The first part gives a short theoretical overview while more details are offered in the Metrohm Monograph Conductometry. The second, practice-oriented part deals with the following subjects:Conductivity measurements in general; Determination of the cell constant; Determination of the temperature coefficient; Conductivity measurement in water samples; TDS – Total Dissolved Solids; Conductometric titrations;

This Application Bulletin describes a polarographic method for the determination of cyanide that allows to determine free cyanide fast and accurately. The determination also succeeds in solutions containing sulfides, where other methods fail. Cyanide concentrations in the range b(CN–) = 0.01...10 mg/L cause no problems. Interference caused by anions and complexed cyanides has been investigated.

Wine sometimes contains heavy metals which can be precipitated out by the addition of potassium ferrocyanide. Generally, these are quantities of iron ranging between 1 and 5 mg, and exceptionally up to 9 mg Fe/L. Zinc, copper, and lead – in descending order of content – may also be present. To estimate the quantity of potassium ferrocyanide necessary for the «décassage of the wine», only very complicated and relatively inaccurate methods have been described until now.This Bulletin permits accurate results to be obtained easily with a simple instrumentation. The results are available in a short time.

Cadmium, lead, and copper can be determined simultaneously in oxalate buffer by anodic stripping voltammetry (ASV) after digestion with sulfuric acid and hydrogen peroxide. Tin present in the sample does not interfere with the determination of lead.For the voltammetric determination of tin please refer to Application Bulletin no. 176.

Cu2+, Co2+, Ni2+, Zn2+, and Fe2+/Fe3+ are determined simultaneously. Interference due to the presence of other metals is mentioned, and methods given to eliminate it. The threshold of determination is ρ = 20 µg/L for Co and Ni, and ρ = 50 µg/L each for Cu, Zn, and Fe.

This Application Bulletin describes methods for the polarographic and voltammetric determination of small quantities of chromium in water, effluent water and biological samples. Methods for the sample preparation for various matrices are given.

In the past, selenium determinations have always been either unreliable or have required complicated methods. However, as selenium is on the one hand an essential trace element (vegetable and animal tissues contain about 10 μg/kg), while on the other hand it is very toxic (threshold value 0.1 mg/m3), it is very important to cover determinations in the micro range. Cathodic stripping voltammetry (CSV) enables selenium to be determined in mass concentrations down to ρ(Se(IV)) = 0.3 μg/L.

Bromide is removed from the sample as BrCN by distillation. The BrCN is absorbed in sodium hydroxide solution and decomposed with concentrated sulfuric acid, then the released bromide ions are determined by potentiometric titration with silver nitrate solution. Iodide does not interfere with the determination.Iodide is oxidized to iodate by hypobromite. After destruction of the excess hypobromite, the potentiometric titration (of the iodine released from iodate) is carried out with sodium thiosulfate solution. Bromide does not interfere, even in great excess.The described methods allow the determination of bromide and iodide in the presence of a large excess of chloride (e.g., in brine, seawater, sodium chloride, etc.).

It has been known for years that consuming too much nitrates from foodstuffs can result in cyanosis, particularly for small children and susceptible adults. According to the WHO standard, the hazard level lies at a mass concentration c(NO3-) ≥ 50 mg/L. However, more recent studies have shown that when nitrate concentrations in the human body are too high, they can (via nitrite) result in the formation of carcinogenic and even more hazardous nitrosamines.Known photometric methods for the determination of the nitrate anion are time-consuming and prone to a wide range of interferences. With nitrate analysis continually increasing in importance, the demand for a selective, rapid, and relatively accurate method has also increased. Such a method is described in this Application Bulletin. The Appendix contains a cselection of application examples where nitrate concentrations have been determined in water samples, soil extracts, fertilizers, vegetables, and beverages.

"A sensitive methods to determine manganese is described. It is primarily suitable for the investigation of ground, drinking and surface waters, in which the concentration of manganese is important. The method can naturally also be used for trace analysis in other matrices.Manganese is determined in an alkaline borate buffer by the anodic stripping voltammetry (ASV). Interference by intermetallic compounds is prevented by the addition of zinc ions in the sample. The limit of determination lies at b(Mn) = 2 µg/L."

This bulletin describes the determination of calcium, magnesium, and alkalinity in water by complexometric titration with EDTA as titrant. It is grouped into two parts, the potentiometric determination and the photometric determination.There are multiple definitions of the different types of water hardness. In this Application Bulletin, the following definitions are used: alkalinity, calcium hardness, magnesium hardness, total hardness, and permanent hardness. Explanations of these definitions and other expressions are provided in the Appendix.Determination of alkalinity during the photometric part is carried out in a separate acid-base titration before the complexometric titration of calcium and magnesium in water. Permanent hardness can be calculated from these values. The determination of calcium and magnesium in beverages (fruit and vegetable juices, wine) is also described.The photometric part includes the determinations of total and calcium hardness and thereby indirectly magnesium hardness using Eriochrome Black T and calconcarboxylic acid as indicators (in accordance with DIN 38406-3).

This Bulletin describes a simple polarographic method for the determination of quinine in drinks and tablets. Whereas in drinks quinine can be determined directly, in the case of tablets it must first be extracted. The limit of quantification is 0.2 mg/L or 4 μg/tablet.

Nitrite can be determined polarographically after its conversion to diphenylnitrosamine (C6H5)2NNO. Potassium thiocyanate is used as a catalyst in order for the conversion to proceed rapidly and quantitatively. The reaction takes place in acid solution at a pH value of approx. 1.5. The limit of quantification is 5 μg/L NO2-.

After acid digestion, the sample solution is neutralized with sodium hydroxide to form sodium dihydrogen phosphate. An excess of lanthanum nitrate is added and the released nitric acid is then titrated with sodium hydroxide solution.NaH2PO4 + La(NO3)3 → LaPO4 + 2 HNO3 + NaNO3This determination method is suitable for higher phosphate concentrations.

Potentiometric titration is an accurate method for determining chloride content. For detailed instructions and troubleshooting tips, download our Application Bulletin.

This Application Bulletin describes a voltammetric method for the determination of aluminum in water samples, dialysis solutions, sodium chloride solutions and digestion solutions (e.g. of lyophilisates). The method utilizes the complexation of the Al3+ ion by Calcon (Eriochrome blue black R). The formed complex can easily be reduced electrochemically at 60 °C. The limit of quantitation depends on the purity of the reagents used and is approx. 5 µg/L.

Although the known photometric methods for the determination of ammonia/ammonium are accurate, they require a considerable amount of time (Nessler method 30 min, indophenol method 90 min reaction time). A further disadvantage of these methods is that only clear solutions can be measured. Opaque solutions must first be clarified by time-consuming procedures. These problems do not exist with the ion-selective ammonia electrode. Measurements can be easily performed in waste water, liquid fertilizer, and urine as well as in soil extracts. Especially for fresh water and waste water samples several standards, such as ISO 6778, EPA 350.2, EPA 305.3 and ASTM D1426, describe the analysis of ammonium by ion measurement. In this Application Bulletin, the determination according to these standards is described besides the determination of other samples as well as some general tips and tricks on how to handle the ammonia ion selective electrode. Determination of ammonia in ammonium salts, of the nitric acid content in nitrates, and of the nitrogen content of organic compounds with the ion-selective ammonia electrode is based on the principle that the ammonium ion is released as ammonia gas upon addition of excess caustic soda:NH4+ + OH- = NH3 + H2OThe outer membrane of the electrode allows the ammonia to diffuse through. The change in the pH value of the inner electrolyte solution is monitored by a combined glass electrode. If the substance to be measured is not present in the form of an ammonium salt, it must first be converted into one. Organic nitrogen compounds, especially amino compounds are digested according to Kjeldahl by heating with concentrated sulfuric acid. The carbon is oxidized to carbon dioxide in the process while the organic nitrogen is transformed quantitatively into ammonium sulfate.

Potassium is one of the most common elements and can be found in many different minerals and other potassium compounds. It is of importance for humans, animals and plants as it is an essential mineral nutrient and involved in many cellular functions like cell metabolism and cell growth. For these reasons, it is important to be able to declare the potassium content of food or soil to reduce problems that may arise by a potassium deficiency or extensive consumption.This bulletin describes an alternative to flame photometric method using an ion selective electrode and direct measurement or standard addition technique. Several potassium determinations in different matrices using the combined potassium ion-selective electrode (ISE) are presented here. Additionally, general hints, tips and tricks for best measurement practice are given.

This Application Bulletin gives an overview of the coulometric water content determination according to Karl Fischer.Amongst others, it describes the handling of electrodes, samples, and water standards. The described procedures and parameters comply with the ASTM E1064.

As the determination of the exact content of individual glycerides in fats and oils is difficult and time-consuming, several fat sum parameters or fat indices are used for the characterization and quality control of fats and oils. Fats and oils are not only essential for cooking, they are also an important ingredient in pharmaceuticals and personal care products, such as ointments and creams. Consequently, several norms and standards describe the determination of the most important quality control parameters. This Application Bulletin describes eight important analytical methods for the following fat parameters in edible oils and fats:Determination of water content in accordance with the Karl Fischer method; Oxidation stability in accordance with the Rancimat method; Iodine value; Peroxide value; Saponification value; Acid value, free fatty acids (FFA); Hydroxyl number; Traces of nickel using polarography; Special care is taken to avoid chlorinated solvents in these methods. Also, as many of the mentioned methods as possible are automated.

"Molybdenum is an essential trace element for plant growth. Since it occurs in natural waters only in trace amount, a very sensitive method of determination is needed. Using the following polarographic method, it is possible to determine 5·10-10 mol/L resp. 50 ng/L.The principle of the method is based on the reaction between the molybdate ion MoO42- and the complexing agent 8-hydroxy-7-iodo-quinoline-5-sulfonic acid (H2L) to form a MoO2L22- complex, which is adsorbed on the mercury electrode. The adsorbed Mo(VI) is reduced electrochemically to the Mo(V) complex. The hydrogen ions present in the solution oxidize Mo(V) again spontaneously to form the Mo(VI) complex, which is thus newly available for electrochemical reduction. This catalytic reaction is the reason for the high sensitivity of the method.Tungsten W(VI) exhibits practically the same electrochemical behavior as molybdenum, but is not described in detail in this Application Bulletin."

In most electrolytes the peak potentials of lead and tin are so close together, that a voltammetric determination is impossible. Difficulties occur especially if one of the metals is present in excess.Method 1 describes the determination of Pb and Sn. Anodic stripping voltammetry (ASV) is used under addition of cetyltrimethylammonium bromide. This method is used when:• one is mainly interested in Pb• Pb is in excess• Sn/Pb ratio is not higher than 200:1According to method 1, Sn and Pb can be determined simultaneously if the difference in the concentrations is not too high and Cd is absent.Method 2 is applied when traces of Sn and Pb are found or interfering TI and/or Cd ions are present. This method also uses DPASV in an oxalate buffer with methylene blue addition.

The determination of the physical and chemical parameters as electrical conductivity, pH value, p and m value (alkalinity), chloride content, the calcium and magnesium hardness, the total hardness, as well as fluoride content are necessary for evaluating the water quality. This bulletin describes how to determine the above mentioned parameters in a single analytical run.Further important parameters in water analysis are the permanganate index (PMI) and the chemical oxygen deman (COD). Therefore, this Bulletin additionally describes the fully automated determination of the PMI according to EN ISO 8467 as well as the determination of the COD according to DIN 38409-44.

Maleic and fumaric acid can be reduced electrochemically to succinic acid. In acidic solutions a differentiation of the two acids is not possible since both are reduced at the same potential. On the other hand, separation at pH 7.8...8.0 is easily possible since fumaric acid is now more difficult to reduce at the lower proton concentration (as a result of cis-trans isomerism) than maleic acid.

The formol number represents a further parameter for the characterization of fruit and vegetable juices. As this is merely an index (the formalin number does not deal with the molecular size, nor with the quantity of amino acids), the conditions of the titration can be adapted to meet practical needs. This concerns mainly the pH value of the endpoint of the SET titration (pH = 8.5, pH = 9.0, pH = 9.2, etc.).

This Bulletin describes the voltammetric determination of aluminum in water samples down to a concentration of 1 μg/L. An aluminum complex is formed with alizarin red S (DASA) and enriched at the HMDE. The following determination employs differential pulse adsorptive stripping voltammetry (DP-AdSV). Disturbing Zn ions are eliminated by addition of CaEDTA.

This Bulletin, using practical examples, indicates how the user can achieve optimum pH measurements. As this Bulletin is intended for actual practice, the fundamentals - which can be found in numerous books and publications - are treated only briefly.

After the degradation of biological samples (e.g. milk, wool, etc.), it is often important to know the cystine/cysteine ratio. This Application Bulletin describes the simultaneous, polarographic determination of the two amino acids. The determination is performed in perchloric acid solution at the DME. Samples with a high protein content require that the determination is performed in an alkaline solution.

Formaldehyde can be determined reductively at the DME. Depending on the sample composition it may be possible to determine the formaldehyde directly in the sample. If interferences occur then sample preparation may be necessary, e.g. absorption, extraction, or distillation.Two methods are described. In the first method formaldehyde is reduced directly in alkaline solution. Higher concentrations of alkaline or alkaline earth metals interfere. In such cases the second method can be applied. Formaldehyde is derivatized with hydrazine forming the hydrazone, which can be measured polarographically in acidic solution.

This document outlines Rancimat testing for both liquid and solid food samples, including direct and PEG methods, for oxidation stability QC in the food industry.

This Application Bulletins describes the determination of nicotinamide (vitamin PP), a vitamin of the B series. Instructions for the determination in solutions (e.g. fruit juice), vitamin capsules and multivitamin tablets are given. The linearity range of the determination is also specified. The limit of detection is approximately 50 μg/L nicotinamide.

This Application Bulletin describes the polarographic determination of folic acid, a vitamin of the B series, also known as vitamin B9 or vitamin BC. Instructions for the determination in solutions (e.g. fruit juice), vitamin capsules and multivitamin tablets are given. The linear range of the determination is also specified. The limit of detection is approx. 75 µg/L folic acid.

This Application Bulletins describes the polarographic determination of thiamine (vitamin B1). The procedure allows an analysis in monovitamin preparations. The linear range of the determination is also given. The limit of detection is approx. 50 µg/L thiamine.

This Application Bulletin describes the polarographic determination of riboflavin (vitamin B2). The procedure allows an analysis in monovitamin preparations. The limit of determination is approx. 100 μg/L.

This Bulletin gives a survey of standard methods from the field of water analysis. You will also find the analytical instruments required for the respective determinations and references to the corresponding Metrohm Application Bulletins and Application Notes. The following parameters are dealt with: electrical conductivity, pH value, fluoride, ammonium and Kjeldahl nitrogen, anions and cations by means of ion chromatography, heavy metals by means of voltammetry, chemical oxygen demand (COD), water hardness, free chlorine as well as a few other water constituents.

This Application Bulletins describes the polarographic determination of pyridoxine (vitamin B6). The method given allows determination in monovitamin and in some multivitamin preparations. The linear range of the analysis is also specified. The limit of detection is approx. 100 µg/L pyridoxine · HCI.

The Bulletin describes the determination of the following parameters in wine: pH value, total titratable acid, free sulfurous acid, total sulfurous acid as well as ascorbic acid (vitamin C) and other reductones.

This Bulletin describes the determination of arsenic by anodic stripping voltammetry (ASV) at the rotating gold electrode. A determination limit of 0.5 μg/L can be achieved with 10 mL sample solution. A differentiation between the As(III) concentration and the total arsenic concentration can be made by appropriate selection of the deposition potential. The analyses are performed with a special gold electrode whose active surface is located laterally; c(HCl) = 5 mol/L is used as supporting electrolyte. For the determination of the total arsenic content, As(III) and As(V) are reduced at -1200 mV by nascent hydrogen to As0, which is preconcentrated on the electrode surface. If the deposition is carried out at -200 mV then only As(III) is reduced; this allows the differentiation between total arsenic and As(III). During the subsequent voltammetric determination the preconcentrated As0 is again oxidized to As(III).

The standard method postulated by DIN 38406 Part 16 describes the determination of Zn, Cd, Pb, Cu, Tl, Ni, and Co in drinking, ground, surface and precipitation (e.g. rain) water. Because the presence of organic substances in the water samples can strongly interfere with the voltammetric determination, a pretreatment with UV digestion using hydrogen peroxide is necessary. This digestion ensures the elimination of all organic substances without introduction of blank values. These methods can, of course, also be applied for trace analysis in other materials, e.g. trace analysis in the production of semiconductor chips based on silicon. Zn, Cd, Pb, Cu, and Tl are determined on the HMDE by means of anodic stripping voltammetry (ASV), Ni and Co by means of adsorptive stripping voltammetry (AdSV).

The effectiveness of antioxidants can be expressed as antioxidant activity. It can be readily determined using the Rancimat method. This is accomplished by first determining the induction time of a mixture made up of hog fat and the antioxidant to be investigated and then by determining the corresponding time for hog fat alone. The quotient expresses the efficiency of the respective antioxidant and is referred to as the antioxidant activity index (AAI).This Application describes the determination of the antioxidant activity index of five common antioxidants.

This Bulletin describes a simple method for the determination of the calcium content in dairy products. The use of CuEGTA and the ion-selective copper electrode (Cu ISE) as indicator electrode allows the determination to be performed without time-consuming sample preparation. If the complexing agent EDTA is used as titrant instead of EGTA, the sum of calcium and magnesium is obtained. The magnesium content can then be calculated from the difference between the results of the two titrations.

Determination of the oxidation stability of foods with a low fat content is a challenge. As an alternative, the oxidation stability can be specified indirectly. To accomplish this, a determination is made as to the extent that a sample that has been mixed with a fat as a standard solution, e.g., hog fat, will change the oxidation stability of that standard solution. This is accomplished by first determining the induction time of the mixture made up of hog fat and the sample and then by determining the corresponding time for the lard alone. The quotient is referred to as the stability index (SI).

Chlorine is frequently added to drinking water for disinfection. Depending on the reactivity and the concentration of chlorine, toxic disinfection by-products (DBPs) can thereby be released. Therefore, it is necessary to strictly control the chlorine concentration in the drinking water. This Application Bulletin shows how to determine the chlorine concentration according to three standard methods: DIN EN ISO 7939-1, APHA 4500-Cl Method B, and APHA 4500-Cl Method I.

This Application Bulletin describes the determination of titanium by adsorptive stripping voltammetry (AdSV) using mandelic acid as complexing agent. The method is suitable for the analysis of ground, drinking, sea, surface and cooling waters, in which the concentration of titanium is of importance. The methods can, of course, also be used for the trace analysis in other matrices.The limit of detection is approx. 0.5 µg/L.

Generally speaking, the gas extraction or oven method can be used for all samples which release their water when they are heated up. The oven method is indispensable in cases in which the direct volumetric or coulometric Karl Fischer titration is not possible, either because the sample contains disruptive components or because the consistency of the sample makes it very difficult or even impossible to transfer it into the titration vessel.The present Application Bulletin describes automatic water content determination with the aid of the oven technique and coulometric KF titration, using samples from the food, plastic, pharmaceutical and petrochemical industry.

In an acidic solution (containing NH4F * HF, Al(NO3)3 / KNO3) sodium forms NaK2AlF6 which precipitates in an exothermic solution, enabling analysis by thermometric titration. Several foods were analyzed, namely bouillon, gravy, tomato ketchup, corn chips, pretzel sticks as well as crackers. The reproducibility of the results was good. After weighing in and adding solutions, samples were crushed with a polytron to ensure homogeneity in the measuring solution. Relative standard deviations were between 0.08% and 3.75%. In addition to this application bulletin, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

In titration, the titrant reacts with the analyte either exothermically (gives off heat) or endothermically (absorbs heat). The Thermoprobe measures the temperature change during titration. When all of the analyte has reacted with the titrant, the temperature of the solution will change, and the endpoint of the titration is indicated by an inflection in the temperature curve. Catalytically enhanced titrations using paraformaldehyde as catalyst are based on the endothermic hydrolysis of the paraformaldehyde in the presence of excess hydroxide ions. Edible oils are dissolved in a mixture of toluene and 2-propanol (1:1) and titrated with standardized TBAH (0.01 mol/L) in 2-propanol to a catalytically enhanced endpoint.

This Application Bulletin describes two methods for the determination of iron at the Multi Mode Electrode.Method 1, the polarographic determination at the DME, is recommended for concentrations of β(Fe) > 200 μg/L. For this method the linear range is up to β(Fe) = 800 μg/L.For concentrations < 200 μg/LMethod 2, the voltammetric determination at the HMDE, is to be preferred. The detection limit for this method is β(Fe) = 2 μg/L, the limit of quantification is β(Fe) = 6 μg/L. The sensitivity of the method cannot be increased by deposition.Iron(II) and iron(III) have the same sensitivity for both methods.These methods have been elaborated for the determination of iron in water samples. For water samples with high calcium and magnesium concentrations such as, for example, seawater, a slightly modified electrolyte is used in order to prevent precipitation of the corresponding metal hydroxides. The methods can also be used for samples with organic loading (wastewater, beverages, biological fluids, pharmaceutical or crude oil products) after appropriate digestion.

This bulletin deals with the automated determination of calcium and magnesium in commercially available finished milk products using a 859 Titrotherm and a 814 USB Sample Processor. Calcium and magnesium in milk can be rapidly and easily titrated thermometrically using a standard solution of Na4EDTA as titrant.Thermometric titrations are conducted under conditions of constant titrant addition rate. The molarity of the titrant is computed automatically in tiamo (software) using the SLO command. Results are reported as mg Ca and Mg/100 mL.

This bulletin discusses automated determination of sodium in milk products available to the public using a 859 Titrotherm and a 814 USB Sample Processor. The sodium content of milk can be rapidly and easily titrated thermometrically with a standard solution of Al3+ as titrant. Thermometric titrations are conducted under conditions of constant titrant addition rate. The molarity of the titrant is computed automatically in tiamoTM (software) with the SLO command. Results are reported as mg Na/100 mL. In addition to this application bulletin, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

This Application Bulletin provides information regarding the MATi 10 (Metrohm Automated Titration) system. MATi 10 is a completely configured system for automatic volumetric Karl Fischer titration with which the water content in liquid and solid samples can be determined. Up to 24 samples can be analyzed directly in 75 mL titration vessels. The samples are weighed into the titration vessels and covered with an aluminum foil. This prevents falsification of the water content.

The Rancimat method determines the oxidation stability (OSI) and antioxidant capacity (SI) of solid foods. OSI measurements are performed directly, with extracted isolated fat, or via the polyethylene glycol method. SI can be determined when the sample is mixed with a reference of antioxidant-free fat.

This Application Bulletin describes the determination of arsenic in water samples by anodic stripping voltammetry using the scTRACE Gold sensor. This method makes it possible to distinguish between As(total) and As(III). With a deposition time of 60 s, the limit of detection for As(total) is 0.9 µg/L, for As(III) it is 0.3 µg/L.

MATi 11 (MATi = Metrohm Automated Titration) is a completely configured system for water content determination in solid or liquid samples using automated volumetric Karl Fischer titration. It contains a Polytron PT 1300 D for the homogenization of the samples. Up to 53 samples are analyzed directly in 120 mL titration beakers. The samples are weighed in the titration beaker and sealed with aluminum foil and a foil holder so that they neither lose nor absorb water.

This Application Bulletin describes the determination of inorganic mercury in water samples by anodic stripping voltammetry using the scTRACE Gold sensor. With a deposition time of 90 s, calibration is linear up to a concentration of 30 µg/L; the limit of detection lies at 0.5 µg/L.

This Application contains information regarding titer determination in Karl Fischer titration, in particular regarding the water standard suitable for a titer determination and for the correct handling of the same.Titer determination for Karl Fischer titrants is indispensable, because the titer is subject to changes caused by the humidity in the air. The frequency of the determination depends on the titrant and the tightness of the system.The titer has the unit mg/mL in Karl Fischer titration. The value calculated in a titer determination indicates how many milligrams of water react on one milliliter of titrant.

Copper is one of the few metals which is available in nature also in its metallic form. This and the fact that it is rather easy to smelt led to intense use of this metal already in the so-called Copper and Bronze Age. Nowadays, it is more important than ever, because of its good electrical conductivity and its other physical properties. For plants and animals, it is an essential trace element; for bacteria, in contrast, it is highly toxic.This Application Bulletin describes the determination of copper by anodic stripping voltammetry (ASV) using the scTRACE Gold electrode. With a deposition time of 30 s, the limit of detection is about 0.5 μg/L.

This Application Bulletin describes the methods for the determination of uranium by adsorptive stripping voltammetry (AdSV) according to DIN 38406 part 17. The method is suitable for the analysis of ground, drinking, sea, surface and cooling waters, in which the concentration of uranium is of importance. The methods can, of course, also be used for the trace analysis in other matrices.Uranium is determined as chloranilic acid complex. The limit of detection in samples with low chloride concentration is about 50 ng/L and in seawater about 1 µg/L. Matrices with high chloride content can only be analyzed after reduction of the chloride concentration by means of a sulfate-loaded ion exchanger.

This Application Bulletin describes the voltammetric determination of the elements iron, copper and vanadium. Fe as well as Cu and V can be determined as catechol complex at the HMDE by adsorptive stripping voltammetry (AdSV). Fe(II) and Fe(III) are determined as Fe(total) with the same sensitivity for both species in either phosphate buffer or PIPES electrolyte. Cu and V can be determined in PIPES buffer.The methods are primarily suitable for the investigation of ground, drinking and surface waters, in which the concentration of these metals is important. But the methods can naturally also be used for trace analysis in other matrices.The limit of detection for all three elements in PIPES buffer is 0.5 ... 1 µg/L, for iron in phosphate buffer it is approx. 5 µg/L.

Lead is known to be highly toxic and lead salts are easily absorbed by creatures. By interfering with enzyme reactions,lead can affect all parts of the human body. It can cause severe damage to brain and kidneys and can cross the bloodbrain barrier. Cases of chronic lead poisoning caused by lead metal used in the water piping system are well known. Therefore, the control of drinking water for lead content is of utmost importance. In many countries (e.g., EU, USA), the limit for lead in drinking water is between 10 and 15 μg/L. These concentrations can reliably be determined with the method described in this Application Bulletin. The determination is carried out by anodic stripping voltammetry at a silver film applied to the scTRACE Gold electrode.

Heavy metals, particularly cadmium and lead, are known to be highly toxic to humans. Therefore, controlling the cadmium and lead content in drinking water is of utmost importance. In many countries, the limit in drinking water for cadmium is between 3–5 µg/L, and for lead it is between 5–15 µg/L. These trace concentrations can reliably be determined with the method described in this Application Bulletin. The determination is carried out by anodic stripping voltammetry (ASV) using the non-toxic Bi drop electrode in a slightly acidic electrolyte.

Iron is an essential element in the human diet and is found in many natural and treated waters. Therefore, the World Health Organization (WHO) does not issue a health-based guideline value for iron. Higher concentrations of iron in surface waters can indicate the presence of industrial effluents or outflow from other operations and sources of pollution. Because of this, precise, rapid, and accurate iron determination at low concentrations in environmental and industrial samples is of great importance. This can be achieved with the method described in this Application Bulletin.

Cobalt is an essential element for humans because it is a component of vitamin B12. While small overdoses of cobalt compounds are only slightly toxic to humans, larger doses from 25–30 mg per day may lead to skin, lung, and stomach diseases, as well as liver, heart, and kidney damage, and even cancerous growths. The same is valid for nickel, which can lead to inflammation at higher concentrations. Drinking a large amount of water containing nickel can cause discomfort and nausea. In the EU the legislation specifies 0.02 mg/L as the limit value for the nickel concentration in drinking water. This concentration can be reliably determined with the method described in this Application Bulletin.

This method is applicable to all samples containing glycerin in the absence of other triols or other compounds that react with periodate to produce acidic products. Glycerin may be determined in the presence of glycols. A periodate solution reacts slowly with diols and triols in acidic aqueous media at room temperature. A quantitative amount of formic acid is generated from the reaction with glycerin (a triol). The reaction with diols produces neutral aldehydes. The amount of formic acid generated by this reaction is determined by titration against sodium hydroxide.

Determination of sodium, potassium, calcium, and magnesium in instant baby milk powder using cation chromatography with direct conductivity detection and dialysis for sample preparation.

Determination of sodium, ammonium, potassium, calcium, and magnesium in 4% boric acid using cation chromatography with direct conductivity detection.

Determination of sodium, ammonium, potassium, calcium, and magnesium in betaine using cation chromatography with direct conductivity detection.

Determination of sodium, ammonium, potassium, calcium, and magnesium in a grapefruit soft drink using cation chromatography with direct conductivity detection after advanced dialysis for inline sample preparation.

Determination of sodium, ammonium, potassium, calcium, and magnesium in a functional fruit juice using cation chromatography with direct conductivity detection after advanced dialysis for inline sample preparation.

Determination of sodium, potassium, calcium, magnesium, putrescine, cadaverine, and histamine in a wine sample using cation chromatography with direct conductivity detection.

Determination of dimethylamine (DMA), trimethylaminoxide (TMAO), trimethylamine (TMA), putrescine, cadaverine, and histamine in a fish sample using cation chromatography with direct conductivity detection.

Determination of choline in infant milk powder using cation chromatography with direct conductivity detection applying Metrohm Inline Dialysis.

Determination of sodium, potassium, magnesium, and calcium in orange juice using cation chromatography with direct conductivity detection applying automated dilution and subsequent Metrohm Inline Ultrafiltration.

Determination of copper, zinc, iron(II), and manganese in red wine using cation chromatography with UV/VIS detection after post-column reaction with PAR.

Determination of lithium, sodium, potassium, calcium, and magnesium in tap water using cation chromatography with direct conductivity detection.

Partial loop injection is a well known way of sample introduction to HPLC. In ion chromatography, it is not yet used to a large extent. Liquid handling with Metrohm's Dosino technology now enables to use partial loop injection on a highly reproducible and accurate level. It includes multi-level calibration out of one standard solution. This Application Note shows its use for parallel anion and cation determination in tap water applying one single Sample Processor. The anion results are shown in Application Note S–287.

Drinking water analysis is strongly regulated by standards. In this Application Note, the cation determination according to ISO 14911 is shown. The Metrosep C 4 - 150/4.0 is the optimum separation column for this purpose.

The determination of cations in tap water is a simple IC application. Here it is used to present Metrohm's intelligent Pick-up Technique (MiPuT). MiPuT enables the injection of volumes of minimum size from very small sample quantities. In the present case, two volumes of 10 µL from a sample 100 µL in size are used for anion and cation analysis, respectively. The calibration takes place through the injection of various volumes of a single standard solution. AN-S-302 describes the corresponding anion determination.

Reducing the analysis time is a demanding task because it is accompanied by a parallel reduction of peak resolution. With a Microbore column 100 mm in length, standard cations in tap water can be determined in only 5 minutes. Strontium can also be determined by simply extending the run time to 6.5 min.

Fast and handsome IC! Outstanding peak shapes on columns with the standard flow rate and a strong eluent. When the high-capacity Metrosep C 6 - 250/4.0 is used, this usually means long retention times. A strong eluent allows however the determination of the cations in drinking water in a short run time with very symmetrical peaks.

The column stability of the Metrosep C 6 - 250/4.0 was determined in long-term laboratory tests. Two injection series per day were run on each of six days in a row. Each series was comprised of nine tap water injections, three check standard injections and six tap water injections. The IC system was shut down on the seventh day of each series. As a whole, the system ran over 10 weeks and counted a total of 2,150 injections. The results show an outstanding reproducibility and verify the high column stability.

Biogenic amines and trimethylamine N-oxide (TMAO) are indicators for the quality of grape fermentation. The consumption of amine-rich wines often leads to headaches, which is why the amine concentrations in wine must be monitored. This Application Note describes the determination of trimethylamine N-oxide, putrescine, cadaverine and histamine, in addition to various standard cations, with the aid of the Metrosep C 6 - 100/4.0 column and subsequent direct conductivity detection.

Ammonia is present in tobacco – either naturally or added – and is realesed during smoking. Ammonia increases the appeal of smoking, and is therefore considered to increase the addictive potential. The determination of ammonium in tobacco is performed by acid extraction and ion chromatographic separation followed by non-suppressed conductivity detection.

Tobacco additives may contain cations like ammonium (see AN-C-168) as well as other cations as counter ions of organic acids. These additives include components to retain moisture and flavor of the tobacco. Ammonium is added to increase the appeal of smoking, and is therefore considered to increase the addictive potential. The determination of cations in tobacco additives is performed by ion chromatographic separation followed by non-suppressed conductivity detection.

Cation analysis in drinking water is a routine task in ion chromatography and can be achieved with a variety of separating columns. The use of a microbore Metrosep C 6 - 250/2.0 column with a high eluent concentration makes it possible to reduce analysis time to less than 12 minutes. Very symmetrical peaks with high sensitivity for the divalent cations are also achieved. Direct conductivity detection is applied.

Chipped wood and sawdust may be used in production of feed e.g., for ruminants. Melamine, a raw material for resins in wood adhesives, is limited to be used in feed. Therefore, the melamine concentration in sawdust has to be analyzed. Melamine determined after ion chromatographic separation with UV/VIS detection.

Whey is the remaining liquid after cheese production. It is mainly used as feed. It is also used as dietary supplement as a beverage or in powder form. This application determines lactic acid as well as cations in one determination. The Metrosep C 6 - 250/4.0 column separates sodium, potassium, magnesium, and calcium by ion exchange. It also acts as an ion-exclusion column, which separates lactic acid. Both lactic acid and the cations can be determined in the same run applying direct conductivity detection. While cations typically elute as negative peaks, lactic acid elutes as an early positive peak. MagIC Net shows both in the usual positive direction.

Microbore ion chromatography offers better sensitivity, shorter retention times, and consumes less eluent, increasing sample throughput and reducing running costs.

Palm oil is a vegetable oil that is used not only in the food industry but also for the manufacture of soaps and body care products. It is furthermore an important raw material for the generation of biodiesel. Depending on the degree of refinement, palm oil can be red, reddish or even colorless in appearance. The carotenes responsible for the color are removed during refinement and the oil becomes increasingly clear. In this Note, the chlorine and sulfur content of various palm oils are determined using Combustion IC.Keyword: pyrohydrolysis

AOF (adsorbable organic fluorine) is used to screen for per- and polyfluorinated alkyl substances in aqueous matrices via pyrohydrolytic combustion and ion chromatography.

In this Application Note, stepwise dissolution measurement (SDM) is applied to aluminum samples coated with different materials, in order to gain insights in corrosion protection. The combination of the Autolab PGSTAT204 with the 1 L Autolab corrosion cell and the NOVA software provides the suitable setup to perform SDM and other corrosion experiments.

In this Application Note, EIS is applied on three coated aluminium samples, before and after the stepwise dissolution measurement (SDM). This technique has been reviewed in the Application Note AN-COR-08.

The concentrations of toxic, biogenic amines in foods, particularly in fish and wine, are an important quality characteristic. The present Application Note shows the separation of putrescine, cadaverine and histamine in addition to the standard cations. Separation takes place on a Metrosep C Supp 1 - 250/4.0 with Dose-in Gradient; quantification via conductivity detection following sequential suppression.

Choline is important for the biosynthesis of numerous molecules, e.g., the neurotransmitter acetylcholine, and exists as an intermediate product in the human metabolism. Concentration determination takes place after microwave digestion. Separation is performed on the Metrosep C Supp 1 - 250/4.0 column following sequential suppression. Separation from the standard cations is outstanding.

Biogenic amines are released during the winemaking process. In wine, they are present as odorless salts. However, in the mouth their flavor is partially liberated, influencing the appearance for the wine taste. Besides this, biogenic amines have been related to lack of hygiene or poor manufacturing practices. The biogenic amines are determined applying suppressed cation chromatography.

This application focuses on the simultaneous analysis of cations and suppressed anions with a dual channel Metrohm IC operated by OpenLab CDS.

This Application Note presents ion chromatography as a precise method to analyze anions in beer as well as cations with non-suppressed conductivity. Automation with Inline Ultrafiltration is also discussed.

By using an enzymatic sensor with a screen-printed electrode, producers can measure lactic acid production, thereby monitoring fermentation processes.

Determination of low levels of chloride (to approximately 5 mg/L Cl-) by thermometric titration.

Determination of free fatty acids (FFA) in oils.

Determination of Na, P, and [Na]/[P] in precursor solutions and solids in the manufacture of sodium tripolyphosphate.

Determination of sodium as chloride in ketchups, sauces and, similar food products.

Determination of sodium in salts, process solutions, and foods.

Iodine value (IV) is a measure of the total number of double bonds present in fats and oils. It is expressed as the «number of grams of iodine that will react with the double bonds in 100 grams of fats or oils». The determination is conducted by dissolving a weighed sample in a non-polar solvent such as cyclohexane, then adding glacial acetic acid. The double bonds are reacted with an excess of a solution of iodine monochloride in glacial acetic acid («Wijs solution»). Mercuric ions are added to hasten the reaction. After completion of the reaction, the excess iodine monochloride is decomposed to iodine by the addition of aqueous potassium iodide solution, which is then titrated with standard sodium thiosulfate solution.

Titration of an unfiltered suspension of the sample with a standardized solution of aluminum containing a stoichiometric excess of potassium ions in the presence of ammonium hydrogen difluoride at ~ pH 3 to give an exothermic reaction, forming insoluble NaK2AlF6. The titrant is standardized against a solution prepared from anhydrous sodium sulfate or sodium carbonate. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube: https://youtu.be/lnCp9jBxoEs

A measured amount of salt is titrated directly with a solution of 1 mol/L tetrasodium EDTA to thermometrically determined endpoints for Ca and Mg. Acetylacetone is added to alter the Ca and Mg EDTA stability constants for better endpoint sharpness.

A measured amount of milk is treated with trichloroacetic acid to coagulate milk solids and liberate calcium and magnesium as dissociated ion. The coagulated milk is filtered or centrifuged, and an aliquot of the clear serum is titrated with a standard solution of 1 mol/L tetra-sodium EDTA to thermometrically determined endpoints for Ca and Mg. Acetylacetone is added to alter the Ca- and Mg- EDTA stability constants for better endpoint sharpness.

Sulfate is precipitated by reaction with an acidified barium chromate solution. The excess barium chromate is precipitated by basification with ammonia solution. Residual soluble chromate equivalent to the sulfate content of the sample is titrated with a solution of standard ferrous ion to a thermometrically determined endpoint.

Sulfate is precipitated as barium sulfate by reaction with an acidified barium chromate solution. The excess barium chromate is precipitated by basification with ammonia solution. Residual soluble chromate, equivalent to the sulfate content of the sample, is titrated with a solution of standard ferrous ion to a thermometrically determined endpoint.

This Application Note describes the determination of total sodium content in canned fish products using thermometric titration. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

This Application Note describes the determination of the total sodium content in instant noodles which are also called «two minute noodles» in some countries. These products contain considerable amounts of sodium (at least 50% of the recommended daily dosage), which means that precise analysis of the sodium content is required. Argentometric titration of the chloride content (assuming that the sodium content in the noodles originates exclusively from the sodium chloride that is added to them) is unsuitable for precise analysis, as the nutrient contents listed on the product packaging document the presence of additional sodium salts other than sodium chloride. Thermometric titration enables fast and direct determination of sodium. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

This Application Note describes the determination of the total concentration of sodium in precursor solutions used in the manufacturing of margarine. The solutions of the precursors are mixed with edible fats and oils to make margarine. Traces of sodium chloride and other sodium and potassium salts may be added to the margarine during this process, usually in the form of emulsifiers, stabilizers, antioxidants, vitamins, coloring agents or flavor enhancers. The analysis of the total sodium content in the precursor solutions is more efficient and cost-effective for the manufacturers than later total sodium content analyses in the final product.As a rule, argentometric titration of chloride is used for indirect determination of the sodium content of foodstuffs. The assumption behind this approach is that the chloride ions are present in a molar ratio of 1:1 with the sodium ions. This is however not the case when – as is usually the case with foodstuffs containing sodium – additional compounds containing sodium are also present in the margarine. The use of potassium chloride as a partial replacement for sodium chloride in some formulations is an additional source of error.The direct titration of sodium by means of thermometric endpoint titration (TET) eliminates these problems. TET is a direct determination method that not only takes into account the entire sodium content present in the solution but is also not hampered by the presence of potassium ions. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

This application note describes the determination of the total sodium content in soy milk products. The methodology may also be applied to the determination of sodium in milk products from cows, goats and sheep. A standard addition technique is employed to permit the accurate and precise determination of sodium at relatively low levels.

This Application Note describes the determination of nitrite using thermometric endpoint titration with sulfamic acid. The nitrite content of a solution can be analyzed down to 0.2 mmol/L.

Sodium can be determined thermometrically in cheese without sample preparation and addition of additives. A homogenizer is responsible for distribution and stirring. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

Nitrate is present in all common agricultural products and due to an extensive use of fertilizers, the nitrate content can be disconcertingly high in vegetables and their fabricated products, like juices. The nitrate content is regulated in many countries because it can form nitrosamines within the human body. Nitrosamines can potentially cause cancer and therefore, the World Health Organization (WHO) has defined an accepted daily intake (ADI) for nitrate of 3.7 mg/kg. To control the nitrate content e.g., in juices, a quick and inexpensive assessment of its concentration is performed via standard addition with a nitrate ion selective electrode . The method can be automated and is faster and less expensive compared to competing chromatographic or spectroscopic methods.

Fluoride content in drinking water can be determined quickly and conveniently with the help of potentiometric titration and the ion-selective fluoride electrode (F-ISE). The F-ISE is calibrated with suitable standard solutions before the measurement.

Determination of the potassium content plays a major role in the food and beverage industry. Potassium is an essential mineral nutrient for humans. It is an important intracellular cation and also plays an important role in processes withincells, where it is involved in the regulation of numerous body functions like blood pressure, cell growth and muscle control.To declare the potassium content of drinks and food, it is usually determined by flame photometric method. However, flame photometry is linear only over a limited concentration range, and often sample dilution is necessary. Furthermore, the instrumentation is rather complex and expensive to buy and maintain. The ion measurement method presented here is a fast, less expensive, and reliable alternative to determine potassium content in beverages.

The determination of the potassium content in foodstuffs plays a major role in the food and dietary supplement industry, as potassium is an essential mineral nutrient for humans. It is an important intracellular cation and also plays a important role in processes within cells, where it is involved in the regulation of numerous body functions like blood pressure, cell growth and muscle control.As a dietary supplement, potassium is present in e.g., electrolyte powder, electrolyte drinks and food supplements. To quantify the potassium content in such products, e.g. flame photometry can be used. In this work, an alternative, ion measurement by standard addition, is described, which is fast, inexpensive and simple to use.

One of the major sources of fluoride intake for humans comes from foodstuff, such as tea. Tea actually has one of the highest potentials to increase the daily fluoride intake. Excessive fluoride intake may lead to dental or skeletal fluorosis. The World Health Organization does not recommend consuming water with a fluoride content higher than 1.5 mg/L. In the presented method according to DIN 10807, the fluoride content can be assessed quickly with an ion selective electrode.

Dissolved oxygen (DO), incorporated into juices during processing, affects quality parameters of the beverage during storage such as Vitamin C concentration, color, and aroma. Various oxygen removal methods are used during juice production, such as vacuum-deaeration or gas sparging to increase product quality and extend shelf life. However, these methods have the drawback that the aroma might be affected since the volatile compounds are also removed. By assessing the DO content in fruit juices, manufacturers can improve the overall product quality. This application note describes a fast and accurate determination of dissolved oxygen in juices by using an optical sensor.

Dissolved oxygen (DO) is generally considered detrimental to wine quality, especially if introduced after fermentation, storage, or bottling. The presence of oxygen after primary fermentation and during the later stages of winemaking can enhance browning reactions, chemical and microbiological instability, and the formation of off-flavors such as acetaldehyde. Knowing the DO content in wine is important through the entire wine production process, because oxidation is a common fault in bottled wines. With the 913 pH/DO meter and the 914 pH/DO/Conductometer, the oxygen content of wine can be determined quickly and easily directly on site.

In municipal water supplies, higher dissolved oxygen (DO) content is desirable because it improves the taste of drinking water. However, high DO levels also speed up corrosion in water pipes. For this reason, industries utilize water with as little DO as possible, and add scavengers such as sodium sulfite to remove any oxygen from a water supply. Municipal water supply pipes are normally coated inside with polyphosphates to protect the metal from contact with oxygen, thus allowing higher DO contents. Therefore, monitoring the DO content online in a water supply is important to assess its DO content to either improve taste or minimize pipe corrosion. Using an optical sensor, such as the O2-Lumitrode, allows a fast and reliable determination according to ISO 17289.

In the food industry, it is essential to determine and monitor certain quality parameters to guarantee consistency. This is especially important for liquid dairy products, which are subject to a strict cold chain. Both the dissolved oxygen (DO) and the pH value have proven to be reliable quality criteria. Oxygen shortens the shelf life and influences the product quality (e.g., nutritional value, color, and flavor). The DO content depends on the salinity in the sample, which is automatically calculated and corrected by the 914 pH/DO/Conductometer during the parallel conductivity measurement. Acidity is another important characteristic to measure that can be checked easily using the pH value. With the 914 pH/DO/Conductometer, all important quality criteria can be monitored with one device.

This Application Note offers an easy way to determine the ammonia content in cacao nibs by using ion measurement, applying the standard addition technique in a reliable cost- and time-saving manner.

Excess sodium intake increases the risk of health issues. Ion-selective electrodes (ISEs) offer a fast, accurate, and cost-effective method for measuring sodium in food.

Groundwater contains many minerals, but can be contaminated by sodium-rich leachate from landfills. Accurate Na determination in water is possible following AOAC 976.25 using the Na-ISE.

The water content of yoghurt powder is determined according to Karl Fischer. Because of the relatively high water and fat content, the sample is prediluted with a 1:1 mixture of chloroform and methanol.

The water content of sweet liquorice is determined according to Karl Fischer. To dissolve the sample, a mixture of methanol and formamide is used as solvent and a high-frequency homogenizer as stirring device.

The water content of lemongrass oil is determined according to Karl Fischer. To prevent unwanted side reactions, special KF reagents for aldehydes and ketones are used and the determination is carried out at 0 ... 4 °C.

The water content of flour is determined according to Karl Fischer. To shorten the analysis times and to obtain more precise results, the determinations are carried out at 50 °C.

The water content of animal fat extract is determined according to Karl Fischer.

The water content of smoked salmon and smoked trout is determined according to Karl Fischer.

The water content of potato chips is determined according to Karl Fischer using the oven method (140 °C).

The water content of spices is determined according to Karl Fischer. To release the water from the cells, a high-frequency homogenizer has to be used.

The water content of margarine is determined according to Karl Fischer.

This Application Note describes the determination of the water content in gelatine using the oven technique.

This Application Note describes the automated determination of the water content in liqueur (30% v/v) using volumetric Karl Fischer titration (MATi 10).

In this application note, Karl Fischer titration is used to determine water content in sodium acetate trihydrate. The MATi 10 allows this determination to be automated, saving users time in the laboratory.

The water content determination by volumetric Karl Fischer titration is one of the most important analyses worldwide. Using an OMNIS system consisting of an OMNIS Titrator and an OMNIS Sample Robot, the fully automatic analysis of water content is possible in various products and matrices. The OMNIS Sample Robot is capable of running several different titrations in parallel. In this Application Note, we present the results of a volumetric Karl Fischer titration run in parallel to an aqueous acid-base titration on the same system. The water content is not influenced by the parallel running aqueous titration, allowing the combination of potentiometric titrations and Karl Fischer titrations on the same automated system.

The vaping and electronic cigarette industries are growing. The mixtures used in these products are usually called e-liquid, e-fluid, or e-juice. Toensure the quality of these e-liquids, testing the most important parameters is required. One important quality control parameter is water or moisture content.Water/moisture content determination by Karl Fischer titration (KFT) is an established and reliable procedure. Compared to other methods the advantages of KFT are its accuracy, speed, and selectivity. For high water content samples, such as e-liquids, volumetric KFT is the method of choice.In this Application Note a system for the fast and reliable determination of the water content in E-liquids is presented. This fully automated system performs the analysis including system preparation, blank, titer, and sample determination completely unattended. Hence, the workload of the operator is reduced to only weighing in the sample and placing the sealed sample vessels on the system.

Water content determination by volumetric Karl Fischer titration is one of the most important analyses worldwide, particularly when it comes to food quality. This parameter has a major influence on the growth of microorganisms, and thus indirectly affects the storability of the raw materials and final products. Consistent quality is only possible with precise measurements during the process. This measurement is performed with the Metrohm Eco KF Titrator for flour, dough, and baked goods.

Karl Fischer reagents contain buffer substances (usually imidazole) since the reaction constant is dependent on the pH value. A constant pH therefore ensures the most repeatable results. In 2015, imidazole was classified by European Union the as a CMR (carcinogenic, mutagenic or toxic) substance and the statement H360D was added, stating possible harm to fertility or a fetus. Meanwhile, other reagents free of imidazole are available for purchase. This Application Note summarizes test measurements with 34433 HYDRANAL™ NEXTGEN Coulomat AG-FI.

Test measurements on water standards are performed with an OMNIS KF Titrator and Karl Fischer reagents Aquagent® Complet 5 and Methanol Fast from Scharlau.

Determination of bromide and bromate in drinking water using anion chromatography with MS detection.

The maximum contaminant concentrations (Maximal Contaminant Level, MCL) of inorganic arsenic and selenium species in drinking water should not exceed 10 and 50 µg/L, respectively. Given that each of the two elements occurs in two oxidation levels – trivalent and pentavalent – a separation step is necessary prior to ICP/MS detection. This Application Note shows the simultaneous determination of the two arsenic (arsenite and arsenate) and selenium species (selenite and selenate). Separation takes place on the Metrosep Dual 3 - 100/4.0 column.

Differentiation between Cr(III) and Cr(VI) is possible following ISO 24384 guidelines by combining ion chromatography with inductively coupled plasma mass spectrometry.

Perchlorate contamination in drinking water may have different sources. Besides natural deposits, anthropogenic sources like fertilizers and rocket fuel residue add to hazardous water contamination. Perchlorate interferes with iodine uptake into the thyroid gland. Newborns and children are particularly vulnerable, affected as thyroid hormones are essential for growth. Besides ion chromatography (IC) followed conductivity detection, IC hyphenated with an MS detector can be used to measure perchlorate down to sub-µg/L levels. In this application IC is hyphenated with a triple-quadrupole MS (IC-MS/MS) for perchlorate determination in order to meet the requirements of EPA 332.0. This IC-MS/MS setup avoids the possible interference of sulfate.

Chlorinating drinking water can form carcinogenic byproducts. EPA Method 557 enables µg/L-level quantification of haloacetic acids using Metrohm IC-MS/MS technology.

During drinking water disinfection with chlorine, chloramine, or ozone, potentially toxic halogenated byproducts can be formed. The disinfectants can react with naturally occurring bromide and/or organic matter in the source water and form one of the most common and highly toxic disinfection byproducts (DBPs): haloacetic acids (HAAs). To protect human health, maximum tolerable levels of HAA in drinking waters are regulated (EPA 816-F-09-004). The EPA Method 557 specifies the analysis of HAAs beside bromate and dalapon by ion chromatography coupled to tandem mass spectroscopy (IC-MS/MS) with LODs varying from 0.02–0.11 µg/L. However, even with single MS, a high sensitivity is achieved to determine the current MCLs within an adequate accuracy. This Application Note describes the analysis of bromate, chlorite, monochloroacetic acid (MCAA), monobromoacetic acid (MBAA), bromochloroacetic acid (BCAA), bromodichloroacetic acid (BDCAA), dibromoacetic acid (DBAA), dichloroacetic acid (DCAA), tribromoacetic acid (TBAA), chlorodibromoacetic acid (CDBAA), and trichloroacetic acid (TCAA) with IC/MS. The Metrohm Driver 2.1 for EmpowerTM offers the analysis as a single software solution with EmpowerTM.

The new DIN draft standard 38407-53 outlines TFA analysis in water using direct injection LC-MS/MS, enabling quantification from 0.1–3.0 μg/L as shown in this Application Note.

Determination of methylarsonic acid and dimethylarsinic acid using anion chromatography with direct conductivity detection.

Determination of chloride, nitrate, phosphate, sulfate, and oxalate in dried potatoes using anion chromatography with direct conductometric detection.

Determination of chloride, nitrate, and sulphate in sugar-containing solutions without matrix elimination using anion chromatography with direct conductometric detection.

Determination of silicate in tap water using anion chromatography with direct conductivity detection.