Nitrogen Kjeldahl analysis

Organic carbon analyses were made in duplicate by a combustion train method in the Microanalytical Laboratory, School of Chemistry, University of Minnesota, and Kjeldahl nitrogen analyses were done in triplicate in the Minnesota State Board of Health Laboratory. Averages of the readings are used here (Table III and VI) and are rounded off to the second decimal. Carbonate was removed from the samples by treatment with 0.5N hydrochloric acid prior to the carbon analyses. 

Bound nitrogen includes all nitrogen-containing compounds, except N2, dissolved in water. Kjeldahl nitrogen analysis, described in Section 7-2, is excellent for amines and amides but fails to respond to many other forms of nitrogen. An automated combustion analyzer converts almost all forms of nitrogen in aqueous samples into NO, which is measured by chemiluminescence after reaction with ozone 17... 

Kjeldahl nitrogen analysis Procedure for the analysis of nitrogen in organic compounds. The compound is digested with boiling H2S04 to convert nitrogen into NHj", which is treated with base and distilled as NH into a standard acid solution. The moles of acid consumed equal the moles of NH3 liberated from the compound. 

L9. Levin, B., and Oberholzer, V. G., Paper electrophoresis of serum proteins with micro Kjeldahl nitrogen analysis of the protein fractions A comparison with free electrophoresis and salt fractionation methods. Am. J. Clin. Pathol. 23, 205 (1953). 

ProMera 10.11 A Kjeldahl nitrogen analysis of a 3.88-mg sample of etlumolamine required 5.73 ml of 0.0110 N hydrochloric acid for titration of the ammonia produced. Calculate the percentage of nitrogen in the compound. 

Elemental analysis is probably the oldest method that has been used to analyze textile finishes. It is still the gold standard in that aU newly developed methods are judged by how well results from the new method compare to results from elemental analysis. Traditional wet chemical methods, such as Kjeldahl nitrogen analysis, continue to have a place in finish analysis. Elemental analysis can be qualitative or quantitative, depending on the need. 

R18. Rodkey, F. L., Tris(hydroxymethyl)aminomethane as a standard for Kjeldahl nitrogen analysis. Clin. Chem. 10, 606-610 (1964). 

Determination of finish add-ons or blend ratios for textiles containing cotton are of prime Interest in textile finishing laboratories. Many approaches have been taken to acquire this information including Kjeldahl nitrogen analysis, other wet chemical determinations, x-ray fluorescence or diffraction (O, and Infrared spectroscopy (2-6). 

Random copolymer synthesis Poly(acrylamide-co-sodium acrylates) (1) were prepared (reaction 5) by ammonium persulfate initiation in distilled water at a 10% monomers concentration at 25°C. The copolymers were isolated by precipitation into methanol, followed by freeze drying. The reactivity ratios were determined and the predicted copolymer composition was in excellent agreement with that experimentally determined by the micro Kjeldahl nitrogen analysis. Molar feed ratios of acrylamide to sodium acrylate varied from 96/4 to 55/45. 

In the Kjeldahl nitrogen analysis, the final product is NH4 in HCl solution. It is necessary to titrate the HCl without titrating the NH4 ion. 

Polyacrylonitrile is one of the components of lacquer coatings used to moistureproof electrical equipment. The nitrile based at 4.48 n has been used by Adams and Swann [ ] for quantitative determination of the coating thickness as this is essentially free of interferences in this case. Samples are run in methyl isobutylketone or toluene and a horizontal baseline is drawn from the solution absorbance at 4.90 /I to 4.48 /x. Only one cell (200 n thick) is used and absorbance (corrected for baseline) is measured to give nitrile content. Standardization is from similar measurements on samples where the nitrile content is determined by Kjeldahl nitrogen analysis. 

As microwave sample preparation has evolved, standard microwave procedures have been developed and approved by numerous standard methods organisations (ASTM, AOAC International, EPA, etc.), see ref. [64]. Examples are standard test methods for carbon black/ash content (ASTM Method D 1506-97), lead analysis in direct paint samples (ASTM Method E 1645-94), etc. Table 8.15 shows some microwave ashing references (detection weight). A French AFNOR method utilises the atmospheric pressure single-mode microwave method as an alternative sample preparation procedure for Kjeldahl nitrogen determination [84], The performance of a microwave-assisted decomposition for rapid determination of glass fibre content in plastics for QC has been described [85]. 

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. 

Potassium sulfate is used in fertilizers as a source of potassium and sulfur, both of which are essential elements for plant growth. Either in simple form or as a double salt with magnesium sulfate, potassium sulfate is one of the most widely consumed potassium salts in agricultural apphcations. It is preferred over potassium chloride for certain types of crops such as, tobacco, citrus, and other chloride—sensitive crops. Some other applications include making gypsum cements to make potassium alum in the analysis of Kjeldahl nitrogen and in medicine. 

The purity of the recrystallized DL-aspartic acid was established by nitrogen analysis by the Kjeldahl and Van Slyke methods. The decomposition point of this product is 325-348°. 

Dry the feces in a vacuum oven overnight, or lyophilize and grind, for nitrogen analysis using a Kjeldahl method (unitbi.2). 

Technicon Instruments Corp. (1977) Digestion and Sample Preparation for the Analysis of Total Kjeldahl Nitrogen and/or Total Phosphorus in Food and Agricultural Products using the Technicon BD-20/40 Block Digestor, Technicon Industrial Method No.369-75A, Technicon Instruments Corporation, New York, USA. 

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