Applikationer

In modern days, a new breed of energetic (explosive) materials is emerging. Traditional aromatic nitrates are still in use, but there is dire need of analytical techniques for energetic materials in the chemical class of peroxides, azo etc. This presentation will demonstrate the use of a modern HPLC system with traditional detector (DAD) and also coupled with mass spectrometry for the analysis of abovementioned various classes of energetic materials.

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.

The pH value and oxidation reduction potential (ORP) of soil provide important information about soil properties, such as solubility of minerals and ion mobility. Knowledge of these properties allows making predictions concerning plant growth, bacterial activity, nutrients that may be needed, possible corrosive effects on buildings, etc.Here, the determination of the pH value is described according to ISO 10390, EN 15933 and ASTM D4972. Th oxidation reduction potential determination is carried out in a suspension.

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.

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.

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.

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.

Determination of traces of gadolinium, samarium, neodymium, cerium, and lanthanum using cation chromatography with direct conductivity detection after Metrohm Inline Filtration.

Organic halides must be monitored in the environment. Combustion ion chromatography (CIC) is used for accurate halogen analysis in solids following EN 17813:2023.

Nitrogen is essential for plant growth. In soil, it can be present in the form of nitrate, ammonium, or urea. Knowing the nitrogen content of soil and in which form it is present helps selecting the right kind of fertilizer to stimulate plant growth.This Application Note shows a fast and reliable way to determine the ammonium concentration in soil by using standard addition.

To assess the quality of a soil it is necessary to know its nutrients. For example, it is necessary that the level of bio-available ions is known as a deficiency might negatively affect plant growth. One of the most important ions is potassiumwhich is directly absorbed in its ionic form by plants roots. It is an essential nutrient and required for proper growth and reproduction.One commonly used method to assess the K content is the extraction of phosphorous and potassium from soil with an acidic, to pH 4.1 buffered solution of calcium acetate, calcium lactate, and glacial acetic acid. This test is called calcium acetate lactate test (CAL-test). Commonly, the extract is analyzed by flame photometric method. In this application note we present a fast and inexpensive alternative using the potassium ion selective electrode.

As a rule, soil contains small percentages of chromium that originate chiefly from rock weathering processes, although anthropogenic sources also exist. The speciation analysis of trivalent – Cr(III) – and hexavalent chromium – Cr(VI) – is important, because the former is a trace element and the latter is highly toxic. The two chromium species are separated as Cr(III)-EDTA-complex and chromate on the Metrosep A Supp 4 - 250/4.0 column. Mass spectrometric isotope dilution analysis (SIDMS) is used for quantification.

Speciation analysis of iron is important, given that its oxidation level has a great influence on environmental response, not only with respect to its absorption by organisms but also to the transport and the storage of the element. Iron(II) and Iron(III) are separated on the Metrosep A Supp 10 S-Guard/4.0 column. IC-ICP/MS with isotope dilution is used for quantification.

Naphtha is the first petroleum product during the distillation process of crude oil or coal tar. It is primarily used as a base material for the production of gasoline or as a solvent. Accidental spills occur regularly at many locations throughout the world, leading to soil contamination.Investigation of contaminated sites is usually performed using gas chromatography, for which the soil sample has to be frozen, grinded, and subsequently extracted prior to the analysis. Using Visible-Near Infrared Spectroscopy such sample preparation steps are not necessary at all, making this method a viable, fast, and simple to use alternative.

The content of organic matter, limestone, silt, clay, and sand, along with pH value and exchangeable calcium and magnesium in soil can be determined in seconds with NIRS.

Metrohm’s MIRA XTR handheld Raman spectrometer enables fast, reagent-free identification of phosphate species, enabling continuous monitoring of dynamic systems.

Raman spectroscopy with PLS modeling enables rapid, accurate, nondestructive quantification of the total phosphate content in solution with minimal sample preparation.

Determination of fluoride, chloride, nitrite, nitrate, and sulfate in soil eluates using anion chromatography with conductivity detection after chemical suppression.

Determination of silicate, sulfate, and phosphate in a clay extract using anion chromatography with conductivity detection before and after chemical suppression. Using a step gradient and switching valve to work with or without chemical suppression.

Determination of nitrite and nitrate in a plant extract using anion chromatography with conductivity detection after chemical suppression.

Soluble tungsten and molybdenum are available in soil mainly as their oxosalts, tungstate and molybdate. Tungstate is rather a hazardous compound, which may interfere with plant growth. Molybdate, on the other hand, is a required micronutrient, required e.g. for nitrate fixation in legumes. Both can easily be determined after alkaline digestion with ion chromatography followed by conductivity detection after chemical suppression.

The rapid growth of the Earth's population has led to massive increases in the consumption of energy and resources and in the production of consumer products and chemicals. It is estimated that 17 million chemical compounds are currently on the market, of which 100,000 are produced on a large industrial scale. Many of these enter the environment. This leads to a demand for sensitive analytical procedures and high-performance analytical instruments.pH value, conductivity and oxygen requirement are important characteristics in water and soil analysis. The first two of these can be determined rapidly; for the third, the titration that is used is also the one used in numerous single determinations. This article describes several important standard-compliant determinations in water and soil analysis.

This Metrohm White Paper presents the important role of electrochemistry in the environmental sciences. The applications have to do with basic research for the fuel cell that yields energy from wastewater, the electrical clean-up of contaminated soil and electrochemical CO2 reduction of greenhouse gases for isolating chemical raw materials.

The coupling of ion chromatography and inductively coupled plasma mass spectrometry (ICP/MS) leads to a high-performance measurement system that masters several particularly challenging analyses. It enables for example reliable determination of element compositions, oxidation states and chemical bonds. This information is used, for example, for assessing the toxicity of medications, environmental and water samples as well as foods and beverages.

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