Applications

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).

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.

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.

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

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.

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).

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.

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.

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

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.

NIR spectroscopy enables fast, reagent-free analysis of fat, moisture, protein, fiber, ash, and starch in animal feed, streamlining quality control with no sample prep.

This study shows how a pre-calibrated NIRS instrument is used for multiparameter analysis of several pet food quality indicators like protein, moisture, fat, and ash.

NIR spectroscopy enables fast, reliable analysis of key quality parameters in alfalfa forage (e.g., protein, fiber, and moisture) without any sample preparation.

Determination of fumarate, lactate, formate, and propionate in animal food using ion-exclusion chromatography with suppressed conductivity detection.

Oxidation stability is an important parameter to assess the quality of animal feed. It provides information about the long-term resistance to degradation of the fatty acids, which can predict the storage stability of the product. Oxidation stability of many animal feeds can be directly and reproducibly measured by the Rancimat method, if polyethylene glycol (PEG) is used as the carrier material.No sample preparation is required for this application. This Application Note describes the determination of oxidation stability of fish food and dog treats. More information on the Rancimat method can be found on the Metrohm website.

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

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

N,N-dimethylglycine is an amino acid derivative found in plants and animals. The respective sodium salt is available as nutritional supplement. In this context it is expected to have athletic performance enhancer effects and acts against fatigue. It is also accepted as a poultry feed addition. The determination is performed applying a Dose-in Gradient with subsequent conductivity detection after sequential suppression. To enhance the selectivity of the separation, a combination of a Metrosep A Supp 7 - 250/4.0 and a Metrosep A Supp 16 Guard/4.0 was used.

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