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Chemical Methods
Published in Jerome Greyson, Carbon, Nitrogen, and Sulfur Pollutants and Their Determination in Air and Water, 2020
Organic nitrogen may be determined by means of a very important and commonly used titrimetric procedure known as the Kjeldahl method. Kjeldahl nitrogen determinations are based on the catalytic conversion*of organic nitrogen to ammonium sulfate, followed by conversion of the ammonium sulfate to ammonium hydroxide by reaction with sodium hydroxide. Heating highly basic ammonium hydroxide solutions can free ammonia according to NH4OH=NH3+H2O
Water quality
Published in David Butler†, John W. Davies††, Urban Drainage, 2000
David Butler†, John W. Davies††
Analytically, organic nitrogen and ammonia are determined together using the Kjeldahl method. In this test, the aqueous sample is boiled to remove any pre-existing ammonia and then digested, during which the organic nitrogen is converted to ammonia. The amount of ammonia produced is then determined as detailed in the next section.
Fundamentals
Published in N.C. Basantia, Leo M.L. Nollet, Mohammed Kamruzzaman, Hyperspectral Imaging Analysis and Applications for Food Quality, 2018
The chemical analysis of food is the subject area concerning the development, application and study of analytical techniques to characterise food and agricultural products (McGorrin, 2006; Nielsen, 2010). These provide information regarding a wide variety of characteristics of foods, including their structure, composition, physicochemical properties and sensory attributes. This data is critical as it enables new product development and quality control, while troubleshooting product problems and customer complaints. However, with the exponentially growing global population and the ever-increasing consumer awareness and concern about the safety, origin, and authenticity of foods, there is exaggerated pressure on food quality managements systems. In addition, traditional (proximate analyses: moisture, ash, fat, protein, carbohydrate) and modern analytical methods (chromatographic, mass spectrometry, and molecular based) employed to characterise food are destructive, require well-trained analysts, are time-consuming and expensive, and often generate harmful waste products. For example, to determine the protein content of food samples, the most commonly used techniques are the Kjeldahl digestion (Kjeldahl, 1883; Sáez-Plaza et al., 2013) and the Dumas combustion (Dumas & Boussingault, 1844) methods. Both these methods are considered the standard, official methods; however, both are destructive, require skilled analysts, and present potentially hazardous situations if not operated correctly. In addition, the Kjeldahl method requires the use of corrosive reagents (such as concentrated sulphuric acid and sodium hydroxide) and produces toxic waste. Similarly, conventional methods for food microbial analyses are regarded as the “gold standard” in many food microbiology laboratories. The conventional culture techniques, although laborious, are still used in the food industry and food-related research because they offer cost effectiveness, ease of use, and familiarity (Gracias & McKillip, 2004). These include a combination of, but are not limited to, culture and colony techniques (Beuchat, 1992; Baird & Lee, 1995), molecular (Feng, 1997; Elmerdahl Olsen, 2000) and immunological methods (Notermans & Wernars, 1991), such as the polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). This multistep approach can be tedious and laborious and is more likely to introduce errors throughout the process. Furthermore, specialised growth media, supplementary staining and microscopy may also be required, which extends the identification of timeframe, prohibiting shipment and sale of the products. Thus, there is a need for rapid, non-destructive analytical techniques for food quality and safety analysis.
Effects of differential degree of chemical modification on the properties of modified starches: Sizing
Published in The Journal of Adhesion, 2018
Sarkodie Bismark, Zhu Zhifeng, Tawiah Benjamin
Kjeldahl method basically comprises three steps: The digestion of the sample, distillation, and titration. Basically, the sample is first digested in strong sulfuric acid in the presence of a catalyst, which helps in the conversion of the amine nitrogen into ammonium ions. The ammonium ions are then converted into ammonia gas, heated, and distilled. The ammonia gas is led into a trapping solution where it dissolves and becomes an ammonium ion once again. Finally, the amount of the ammonia that has been trapped is determined by titration with a standard solution, and a calculation made.
Mineral composition of Atriplex halimus plant as influenced by genotype and thermal regime
Published in International Journal of Phytoremediation, 2021
Leonarda Dessena, Maurizio Mulas
Phosphorous was determined according to the molybdate spectrophotometric method (AOAC 2005) by reading through the UV-VIS spectrophotometer (Hitachi model 100-60, Tokio, Japan) at a wavelength of 650 nm. For nitrogen determination, we used the Kjeldahl method.