Applications

The bromine number and bromine index are important quality control parameters for the determination of aliphatic C=Cdouble bonds in petroleum products. Both indices provide information on the content of substances that react withbromine. The difference between the two indices is that the bromine number indicates the consumption of bromine in gfor 100 g sample and the bromine index in mg for 100 g sample.This Application Bulletin describes the determination of the bromine number according to ASTM D1159, ISO 3839, BS2000-130, IP 130, GB/T 11135 and DIN-51774-1. The bromine index determination for aliphatic hydrocarbons is described according to ASTM D2710, IP 299, GB/T 11136 and DIN 51774-2. For aromatic hydrocarbons the determination of the bromine index is described according to ASTM D5776 and SH/T 1767. UOP 304 is not recommended for the determination of the bromine number or bromine index because its titration solvent contains mercuric chloride.

Only coulometric Karl Fischer titration can determine low water contents with sufficient accuracy.This Application Bulletin describes the direct determination according to ASTM D6304, ASTM E1064, ASTM D1533, ASTM D3401, ASTM D4928, EN IEC 60814, EN ISO 12937, ISO 10337, DIN 51777, and GB/T 11146. The oven technique is described according to ASTM D6304, EN IEC 60814, and DIN 51777.

Anionic surfactants can be titrated with cationic surfactants and vice-versa. The Bulletin describes a multitude of substances that can be determined in this fashion and specifies the respective working conditions and parameters. In contrast to the classic two-phase titration in accordance with Epton, the titration with the anionic and cationic surfactants electrodes can be performed without chloroform. Furthermore, the equivalence point of the titration is difficult to determine in some cases with the Epton method and the titration cannot be automated.In many cases, a surfactant ISE is a remedy that is both environmentally friendly and suitable here. It was developed specially for application with potentiometrically indicated surfactant determinations.

This bulletin describes a procedure to determine the bromine index (BI) using coulometric titration. The bromine index is the fraction of reactive unsaturated compounds (mostly C=C double bonds) in hydrocarbons encountered in the petrochemical industry. The double bonds are split with the attachment addition of bromine.

This Application Bulletin shows the determination of the total base number in petroleum products by applying different titration types according to various standards.

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, iron(II), magnesium, and calcium in an extract of monoethylene glycol using cation chromatography with direct conductivity detection.

Determination of trimethylamine in hydrogen peroxide (31 %) using cation chromatography with direct conductivity detection after inline matrix elimination, inline preconcentration, and inline calibration.

Determination of magnesium, cadmium, and iron in phosphoric acid using cation chromatography with direct conductivity detection.

Lanthanum (La) is a transition metal which oxidizes easily in air to lanthanum(III) oxide. This oxide, as well as salts resulting from its dissolution in acid and recrystallization, is a component of different catalysts. Here, a lanthanum(III) acetate solution prepared by dissolution of lanthanum(III) oxide in acetic acid, has to be tested for a sodium contamination. The high concentration of La3+ is complexed by the dipicolinic acid in the eluent and forms anionic complexes. These complexes are eluted in the front and therefore do not interfere with the sodium impurity as well as other cations such as ammonium and calcium.

Determination of trace levels of cations and amines in hydrogen peroxide is important in quality determination of high-grade semiconductor chemicals. In particular, some manufactures look for 1 ppb trimethylamine or less in hydrogen peroxide samples. Ion chromatography after MiPCT-ME* with conductivity detection after sequential cation suppression is applied.

Determination of acetic anhydride in the presence of acetic acid in acylation mixtures.

A sample of concentrated mineral acid is dissolved in anhydrous acetonitrile, and the water content titrated with a solution of TEOF in acetonitrile. The TEOF reacts exothermically with water in the presence of a strong acid (acting as a catalyst).

A direct thermometric titration (TET) with 2 mol/L NaOH is used to determine the HF, NH4F, and maleic acid (C4H4O4) contents of acid cleaning solutions. Three endpoints (EPs) are obtained, which may be assigned as follows:EP1: C4H4O4 (pKa1 = 1.9), HF (pKa = 3.17)EP2: C4H4O4 (pKa2 = 6.07)EP2: NH4F (pKa = 8.2)The HF content is determined by subtracting the difference (EP2-EP1) from EP1.

This Application Note supplements AN-H-003 with the treatment of the standard addition of sulfate as sulfuric acid. This technique may be contemplated when either sulfate levels are too low for a satisfactory direct titration, or when the sample matrix hinders endpoint detection, leading to poor precision and accuracy.

The water content of methyl ethyl ketone peroxide is determined according to Karl Fischer using two-component reagents in order to prevent unwanted side reactions. (Separate solvent is used to ensure a high excess of sulphur dioxide and amine in the titration vessel.)

The water content of ammonium and potassium peroxodisulphate is determined according to Karl Fischer using two-component reagents. To prevent unwanted side reactions the determinations are carried out at -20 °C. Because the potassium salt is insoluble in the solvent, a high-frequency homogenizer is used to disintegrate the salt particles.

The water content of cyclopropyl methyl ketone is determined according to Karl Fischer by coulometric titration using special reagents for aldehydes and ketones.

The water content of 2-methyl-1,3-butadiene and 2,5-norbornadiene is determined according to Karl Fischer using a special solvent mixture to prevent unwanted side reactions.

The water content of acetophenone and benzophenone is determined according to Karl Fischer using special KF reagents for ketones/aldehydes to prevent unwanted side reactions.

The water content of piperidine and piperazine is determined according to Karl Fischer using a buffered solvent mixture.

Determination of the water content of liquid ammonia according to Karl Fischer after absorption of the water in ethylene glycol.

The water content of aniline is determined according to Karl Fischer in buffered solvent.

The water content in Ca carbonate is determined by volumetric Karl Fischer titration.

Determination of NO3- and ClO4- in the presence of a large excess of HCl using anion chromatography with direct conductivity detection (using time program for full scale change after 18 min).

Determination of carbonate in a solution of methyl-monoethanol-amine with anion chromatography with direct conductivity detection.

Determination of chloride, bromide, and iodide in alkaline combustion solutions using anion chromatography with direct conductivity detection.

Determination of traces of iodide in HCl (25%) using anion chromatography with amperometric detection at a silver electrode.

Determination of traces of bromide in HCl (32%) using anion chromatography with amperometric detection at the silver electrode.

Determination of traces of iodide in acetic acid using anion chromatography with amperometric detection at the carbon paste electrode.

Monoethylene glycol (MEG) is used to remove water from natural gas before further processing. Due to high temperatures applied, glycol degradation to glycolic, formic, and acetic acid may occur. These reactions are unwanted as the emerging acids are corrosive. The determination of the organic acids is achieved by ion-exclusion chromatography with conductivity detection after inverse suppression.

Identification of unknown materials in the field can be a complicated affair, especially in critical situations, where speed, safety, and ease-of-operation are essential. Mira DS, Metrohm Raman’s handheld Raman analyzer, and the intelligent Universal Attachment (iUA) give the user automated Content ID capabilities. Content ID achieves through container identification of unknown materials quickly, easily, and safely.

This application note presents the Orbital Raster Scan (ORS) technology from Metrohm Raman to overcome low resolution, poor sensitivity, and sample degradation while still interrogating a large sample area.

Signal-to-noise ratio, spectrograph design, resolution of MIRA handheld Raman analyzers.

Low frequency Raman spectroscopy extends conventional Raman analysis by capturing vibrational modes down to 65 cm-1, enabling deeper insights into molecular structure, protein characterization, polymorph identification, and phase changes.

Determination of hypophosphite, formate, phosphate, adipate, p-nitrobenzoate, and sebacate in ethylene glycol using anion chromatography with conductivity detection after chemical suppression.

Determination of phosphate and tetrafluoroborate in 2% HF using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride, nitrate, and sulfate in methanol using anion chromatography with conductivity detection after chemical suppression.

Determination of fluoride, chloride, phosphate, and sulfate in boric acid using anion chromatography with conductivity detection after chemical suppression.

Determination of acetate, chloride, nitrate, and sulfate in aluminum oxide using anion chromatography with conductivity detection after chemical suppression.

Determination of acetate and dichloroacetate in chloroacetic acid using anion chromatography with conductivity detection after chemical suppression.

Determination of sulfate in methansulfonic acid (70%) using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride, nitrate, and sulfate in sodium thiocyanate using anion chromatography with conductivity detection after chemical suppression.

Determination of formate, acetate, chloride, benzoate, and oxalate in phenolic extracts using anion chromatography with conductivity detection after chemical suppression.

Determination of adipic acid and phthalic acid in an alkaline ester digestion solution using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride and sulfate in hypophosphoric acid using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride in concentrated nitric acid using anion chromatography with conductivity detection and chemical suppression.

Determination of traces of chloride in a quaternary ammonium hydroxide using anion chromatography with conductivity detection after chemical suppression and inline cation exchange to remove the matrix cations.

Determination of fluoride, chloride, and sulfate in an absorption solution containing H2O2 using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride and bromide in an absorption solution after Wickbold digestion using anion chromatographywith conductivity detection after chemical suppression.

Determination of traces of fluoride and sulfate in 35% hydrochloric acid (HCl) using anion chromatography with conductivity detection after chemical suppression and sample preparation by inline neutralization.

Determination of oxalate, thiosulfate, and thiocyanate in an amine solution using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride, chlorate, and sulfate in soda lye (50% sodium hydroxide) using anion chromatography with conductivity detection after sequential suppression and Metrohm Inline Neutralization.

Determination of chloride, nitrate, and sulfate in 85% H3PO4 using two-dimensional anion chromatography with conductivity detection after sequential suppression.

Determination of molybdate in 2.5% NaCl using anion chromatography with conductivity detection after chemical suppression and inline matrix elimination by molybdate preconcentration after the first separation and subsequent reinjection.

Determination of fluoride, chloride, phosphate, and sulfate in sodium tetraborate using anion chromatography with conductivity detection after sequential suppression. Inline acidification is applied to convert tetraborate into boric acid which is not retained on the preconcentration column. Inline calibration minimizes the anion contamination.

Metrohm Inline Neutralization is a well-established sample preparation technique for anion determinations in hydroxide solutions. The intelligent Partial Loop Injection Technique (MiPT) allows to calibrate the system with one single standard solution and to adjust the injection volume according to the anion concentrations in the sample. This method has been successfully applied to anion analysis in potassium hydroxide (50 and 85%) and in potassium carbonate solutions (83%).

Hydrogen peroxide is used as a cleaning, oxidizing and bleaching agent. Depending on its purity, it may contain inorganic anions as well as organic acid anions, such as oxalate, phthalate, and dipicolinic acid. Dipicolinic acid is a complexing agent that binds transition metal cations and is sometimes added to increase the stability of hydrogen peroxide.

The separation of short-chain organic acids from fluoride and chloride requires diluted eluents. These weak eluents, however, induce long retention times for divalent anions. Adding a stronger eluent later in the separation sequence by use of a Dose-in Gradient makes these anions elute more rapidly. Furthermore, the Dose-in Gradient offers the advantage of low equipment and technical expense.

Within the scope of the modernization of USP, chloride and sulfate are determined as impurities in potassium hydrogen carbonate (bicarbonate). USP41 monograph for potassium bicarbonate does not check for chloride and sulfate. Applying ion chromatography with conductivity detection after sequential suppression allows quantifying these impurities.

Analysis of sodium hydrogen carbonate (also known as sodium bicarbonate) for anionic contaminants is critical due the large amount of CO2 formed during suppression. Even applying sequential suppression does not completely remove the interferences due to the carbonate peak. The introduction of Inline Neutralization applying the Sample Preparation Module (SPM) with subsequent CO2 removal with the MCS (Metrohm CO2 Suppressor) prior to the injection solves the problem. After this pretreatment, the sequentially suppressed sample is analyzed without issues.

The presence of acidic components in volatile solvents could be a result of contamination, decomposition during storage, distribution or manufacture. An increased acid content in solvents could lead to a variety of problems like shorter storage stability or chemical corrosion. Using the Optrode for indication, the acidity is determined by photometric titration with sodium hydroxide as titrant and phenolphthalein as indicator. If the volatile solvent is water soluble, it is dissolved in deionized water, if not, it is dissolved in carbon-dioxide free ethanol.

The bromine index is an important parameter for the determination of aliphatic C=C double bonds in petroleum hydrocarbons. For the titration, a solvent mixture of glacial acetic acid, methanol, and dichloromethane is usually used.In this Application Note, the chlorinated solvent in the solvent mixture was replaced with toluene, resulting in a more environmentally beneficial method in comparison to ASTM D2710 and IP 299.

The bromine index is an important quality control parameter for the determination of aliphatic C=C double bonds in aromatic hydrocarbons and is thus a measure for the presence of aliphatic unsaturation in these materials. In situ generated bromine reacts with the aliphatic double bonds. When the titration is finished an excess of free bromine causes a sudden change in the measured potential thus indicating the equivalence point.

Sodium lactate is a salt form of lactic acid used in many regulated industries—therefore an accurate determination of the lactate content is required and is already covered in several norms. One such monograph by the US Pharmacopoeia (USP) results in high accuracies and well-defined titration curves but uses titrants and solvents that are more costly than necessary. In comparison, the presented modified method from Metrohm requires a 1:1 mixture of water and acetone and uses aqueous hydrochloric acid as titrant, resulting in an estimated cost reduction of 40% per titration compared to the USP method (USP–NF 2021, Issue 2). Furthermore, the time needed for each analysis is reduced to just 12% of the USP method (excluding blank determination). This Application Note presents both methods to determine lactate content and shows the results obtained on an OMNIS system.

Direct titration is a simple and precise way to accurately measure the caffeine content in different nonaqueous products. The OMNIS Titrator equipped with a dSolvotrode reliably determines caffeine through flexible analyses combined with high-end software.

The iodometric back titration is a precise method used to accurately measure the caffeine content in various aqueous samples. Reliable determinations are made easy using the OMNIS Titrator equipped with a dPt Titrode.

Determination of traces of fluoride, bromide, nitrate, phosphate, and sulfate using anion chromatography with conductivity detection after chemical suppression and subsequent UV/VIS detection.

Determination of bromide in calcium chloride using anion chromatography with UV/VIS detection.

Determination of aluminum in phosphoric acid using cation chromatography with UV detection after post-column reaction with catechol violet.

Determination of Fe, Pb, Cd, and Cu in Co(Ac)2 solution using the MME.

Determination of Cr, Mn, and Ti in a PTA solution containing HCl.

Determination of Ni, Co, and Fe in a PTA solution containing HCl.

Determination of Zn, Cd, Pb, Cu, and Cr in triglyceride.

Determination of Cd, Pb, and Sb in acetic acid.

Determination of Zn, Cd, Pb, Ni, and Co in hydrochloric acid (37.8%).

Determination of Zn, Cd, Pb, Ni, and Co in Javelle water.

4-Carboxybenzaldehyde can be reduced directly on the DME in a solution containing ammonium.

Determination of W(VI) in the organic phase after digestion

Cr(VI) is determined with the complexant DTPA at pH 6.2 by adsorptive stripping voltammetry (AdSV) at the HMDE.

Mo is determined by polarography at the SMDE in nitric acid solution.

Zn and Pb are determined by anodic stripping voltammetry (ASV) in acetate buffer at pH 4.6.

Iron can be determined in ethanol by adsorptive stripping voltammetry (AdSV) at the HMDE. PIPES buffer is used as supporting electrolyte and catechol as complexing agent at a pH value of 7.0.

The concentration of nickel in ethylene glycol can be determined by adsorptive stripping voltammetry (AdSV) after the organic matrix is destroyed by UV digestion.

The concentration of Fe(total) is determined in monoethylene glycol by adsorptive stripping voltammetry with 2,3-dihydroxy-naphthalene as complexing agent. The detection limit of the method is approx. 0.1 µg/L with respect to the content in the measuring vessel. If no bromate is added to the supporting electrolyte the sensitivity of the method is about 10 times lower. All reagents have to be added in the order as listed below. Fe(II) and Fe(III) give signals with the same sensitivity. All reagents typically contain iron impurities, especially the 2,3-dihydroxy-naphthalene. Therefore a subtraction of the reagent blank is recommended.

The concentration of Fe is determined polarographically in phosphoric acid. The method is suitable for iron in concentrations in the ppm range. Fe(II) and Fe(III) show signals with the same sensitivity

The concentration of Ni and Co is determined by adsorptive stripping voltammetry at the HMDE with dimethylglyoxime (DMG) as complexing agent.

The concentration of Fe is determined by adsorptive stripping voltammetry at the HMDE with 1-nitroso-2-naphthol (1N2N) as complexing agent.

The concentration of nitrobenzene in aniline is determined by polarography in an ethanol / acetic acid electrolyte.

The presence of copper in fuel ethanol blends has gained considerable attention since Cu2+ catalyzes oxidative reactions in gasoline leading to olefin decomposition and gum formation. Cu2+ in ethanol can easily be determined using anodic stripping voltammetry (ASV) in ethanol/gasoline blends without any sample pretreatment.

This e-book explains how Raman and near-infrared (NIR) spectroscopy enable rapid, nondestructive polymer analysis, ensuring high quality while reducing costs and waste.

Propylene oxide (PO) is a major industrial product used in assorted industrial applications, mainly for the production of polyols (the building blocks for polyurethane plastics). Several production methods exist, with and without co-products. This white paper lays out opportunities to optimize PO production for safer and more efficient processes, higher quality products, and substantial time savings by using online process analysis instead of laboratory measurements.

Underestimation of quality control (QC) processes is one of the major factors leading to internal and external product failure, which have been reported to cause a loss of turnover between 10–30%. As a result, many different norms are put in place to support manufacturers with their QC process. However, time to result and the associated costs for chemicals can be quite excessive, leading many companies to implement near-infrared spectroscopy (NIRS) in their QC process. This paper illustrates the potential of NIRS and displays cost saving potentials up to 90%.

Ion measurement can be conducted in several different ways, e.g., ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP-OES), or atom absorption spectroscopy (AAS). Each of these are well-established, widely used methods in analytical laboratories. However, the initial costs are relatively high. In contrast, ion measurement by the use of an ion-selective electrode (ISE) is a promising alternative to these costly techniques. This White Paper explains the challenges which may be encountered when applying standard addition or direct measurement, and how to overcome them in order for analysts to gain more confidence with this type of analysis.

This white paper summarizes the steps involved in converting an existing manual titration procedure to semi-automated or automated titration procedures. It discusses topics such as selecting the right electrode and titration mode. For a better understanding, the discussion topics are illustrated with three examples.

Ion chromatography mass spectrometry (IC-MS) is a powerful tool that can handle many challenging analytical tasks which cannot be performed adequately by IC alone. IC-MS is a robust, sensitive, and selective technique used for the determination of polar contaminants like inorganic anions, organic acids, haloacetic acids, oxyhalides, or alkali and alkaline earth metals. After separation of the sample components via IC, mass selective detection guarantees peak identity with low detection limits. The inclusion of automated Metrohm Inline Sample Preparation (MISP) allows not only water samples, but also chemicals, organic solvents, or post-explosion residues to be readily analyzed without need for extensive manual laboratory work. This White Paper explains the benefits of IC-MS over IC in certain cases, the hyphenation of IC and different MS systems, as well as related norms and standards.

The objective of validation of an analytical procedure is to demonstrate that it is suitable for its intended purpose. Recommendations for the validation of analytical methods can be found in ICH Guidance Q2(R1) Validation of Analytical Procedures: Text and Methodology and in USP General Chapter <1225> Validation of Compendial Procedures. The goal of this white paper is to provide some recommendations for the validation of titration methods.

This White Paper focuses on selected IC-MS applications for the straightforward identification and quantification of organic acids and inorganic anions in different matrices.