Nitrogen values, Kjeldahl

Protein contents are calculated from Kjeldahl nitrogen values by applying the factor 6.25 as the nitrogen equivalent for protein. However, the nature of the nitrogenous components must be elaborated by further research. In a discus-... 

The value to be used for the protein content is defined as the Kjeldahl nitrogen multiplied by 6.25. Similarly, there are definitions regarding saturated fatty acids. 

For n = 15 cereal samples from barley, maize, rye, triticale, and wheat, the nitrogen contents, y, have been determined by the Kjeldahl method values are between 0.92 and 2.15 mass% of dry sample. From the same samples near infrared (NIR) reflectance spectra have been measured in the range 1100 to 2298 nm in 2nm intervals each spectrum consists of 600 data points. NIR spectroscopy can be performed much easier and faster than wet-chemistry analyses therefore, a mathematical model that relates NIR data to the nitrogen content may be useful. Instead of the original absorbance data, the first derivative data have been used to derive a regression equation of the form... 

The time-dependent changes in total Kjeldahl nitrogen (TKN) in aerobic and anaerobic bioreactors run according to the similar pattern. The final reduction of TKN in aerobic reactor was ca. 93% (Erses et al. 2008), while in the anaerobic reactor the TKN value remained at the high level to the end of the experiment. 

Example Figure 3.1, represents the absolute errors in nitrogen analysis by means of micro Kjeldahl s Method. Here, each vertical line labelled (xj - xt) designates the absolute deviation of the mean of the set from the true value. In Figure 3.1, A represents (xj - xf) the absolute error obtained by analyst-1 for the assay of benzyl-iso-thioureahydrochloride, whereas B represents (x2 - x() the absolute error obtained by analyst-2 for the assay of the same compound. 

Our assumption is that the lower values obtained for nitrogen linked by this fixing method perhaps cannot be determined by the Kjeldahl method. Also, the products obtained mechanochemically and those of the combustion residue may have different structures. 

The total nitrogen of orange juices was found to increase with the maturity of the fruit and ranged between. 068 to. 120 g per 100 ml (30). The actual protein values obtained by Clements (31) were about 20 percent of the acetone powder. Nearly 30 percent of the alcohol-insoluble solids of juice and about 20 percent of that of vesicular pulp were found to be protein as determined by the Kjeldahl procedure (32). These values are the actual protein that was precipitated by alcohol and are only a fraction of the total protein values usually reported for orange juice (8). The main source of proteins in citrus juice is probably in the form of enzymes and the plastids. At least 47 different enzymes have been reported to occur in citrus fruits (33). Citrus fruits also contain several phenolic amines (34), some of which such as syn-epherine, may have physiological importance (35). 

Crude protein and total lysine plus furosine Total nitrogen was determined by macro Kjeldahl digestion and protein estimated as N x 6.25. Total lysine values were obtained from conventional amino acid analyses carried out on 500-mg samples following digestion with 800 ml of 6M HC1 under reflux by use of a Biotronic LC 6000 or Kontron Liquimat III amino acid analyzer. Furosine was determined in the same way using 300 ml 7.8 M HC1 as described in ( 6 ) with an amino acid analyzer ( 7 ). 

Samples of these compounds were separately mixed with D-glucose at various concentrations, and their pH values were checked. Some mixtures were made up in buffer solutions. Total-nitrogen (Kjeldahl) and amino-nitrogen (Pope and Stevens149,16°) determinations were carried out on aliquots of... 

Analysis. The heating value, ash content, and sulfur distribution of the raw and treated coals were determined according to ASTM procedures (7). Iron in the extracts of the raw and treated coals was determined by titration with a cerium (IV) solution. Iron in the residues from the acid extractions of the raw and treated coals was determined spectrophotometrically using ferrozine (20). The liquid extracts were analyzed for total sulfur (as sulfate) by ion chromatography after separation of the sulfate from nitrate on an alumina column (21). Nitrogen was determined in the raw and treated coal and in their nitric acid-extracted residues by a modified Kjeldahl method. 

The nitrogen content was determined with two different methods, elemental analyses and the Kjeldahl method. The Kjeldahl method resulted in significantly lower values for both fuels. All the graphs with results are plotted using the higher nitrogen concentration without making any estimation on the relative accuracy of the two methods. 

The method for the quantitative determination of copovidone given by the Ph.Eur. monograph measures the nitrogen content (theoretical value 7.1%) by the Kjeldahl method. 

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