Investigations of the Kjeldahl Method For the Determination of Nitrogen

Abstract This simple method of centrifugal analysis for total protein in human breast milk is based on the change in the wavelength of the absorbance maximum of Coomassie Brilliant Blue G-250 when the dye is bound to protein. Within-run and between-day CVs were 3.8% and 4.8%, respectively. Compared with a micro-Kjeldahl method for determination of total nitrogen, the coefficient of correlation was 0.99.

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Generic Combustion Method for Determination of Crude Protein in Feeds: Collaborative Study

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/72.5.770 ◽

1989 ◽

Vol 72 (5) ◽

pp. 770-774 ◽

Cited By ~ 19

Author(s):

Rose A Sweeney

Keyword(s):

Crude Protein ◽

Collaborative Study ◽

Combustion Method ◽

Performance Requirements ◽

General Terms ◽

Relative Standard ◽

Kjeldahl Method ◽

Standard Deviations ◽

And Performance

Abstract Nine laboratories participated in a collaborative study on determination of crude protein in animal feeds to compare a generically described combustion method with the AOAC mercury catalyst Kjeldahl method (7.015). The combustion method was written in general terms of method principle, apparatus specifications, and performance requirements. The sample set comprised closely matched pairs of feed ingredients and mixed products ranging from 10 to 90% protein. Ten pairs ground to 0.5 mm were the focus of the study; 4 pairs were ground to 1.0 mm for comparison. Nicotinic acid and lysine monohydrochloride were included as standards. Collaborators were instructed to report their results for performance checks using materials supplied. Only one laboratory failed to meet the proposed limits. Seven laboratories used the LECO Model FP-228 analyzer and 2 used the LECO CHN 600 analyzer. For the 0.5 mm pairs, repeatability standard deviations (sr) ranged from 0.09 to 0.58 for the Kjeldahl method and from 0.14 to 0.33 for the combustion method, with a pooled sr value of 0.28 and relative standard deviation (RSDr) of 0.59%. Reproducibility standard deviations (SR) ranged from 0.23 to 0.86 (Kjeldahl) and from 0.30 to 0.61 (combustion), with a pooled sR value of 0.52 and RSDR of 1.10%. Grand means for the samples ground to 0.5 mm were 47.65% protein by the combustion method and 47.41% protein by the Kjeldahl method. For samples ground to 1.0 mm, corresponding values were 31.82 and 31.50% protein. The generic combustion method has been approved interim official first action.

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XXXIII.—I. On the Estimation of Carbon in Organic Substances by the Kjeldahl Method. II. Its Application to the Analysis of Potable Waters

Transactions of the Royal Society of Edinburgh ◽

10.1017/s0080456800032828 ◽

1895 ◽

Vol 37 (4) ◽

pp. 743-757

Author(s):

Charles Hunter Stewart

Keyword(s):

Accurate Method ◽

Great Accuracy ◽

Organic Substances ◽

Applied Chemistry ◽

Carbon And Nitrogen ◽

Kjeldahl Method ◽

The Will ◽

Time Required

An easy and yet accurate method of determining carbon and nitrogen in organic substances has long been a desideratum, especially among those engaged in the application of chemistry to biological, hygienic, and agricultural questions. For the determination of nitrogen the method of Dumas, with its numerous modifications, is still the only one applicable in all cases, but the time required for it, and the manipulative dexterity necessary, has prevented its wide application for the above-named purposes. The method of Will and Varrentrap, though less generally applicable, is easier, and, until the publication of Kjeldahl's method, was most frequently used in applied chemistry. Kjeldahl claims for his method the same applicability and as great accuracy as the Will and Varrentrap method, with the added advantage of greater ease in working.

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Losses from cattle faeces during chemical analysis

Australian Journal of Experimental Agriculture ◽

10.1071/ea9740716 ◽

1974 ◽

Vol 14 (71) ◽

pp. 716 ◽

Cited By ~ 3

Author(s):

L Falvey ◽

A Woolley

Keyword(s):

Dry Matter ◽

Nitrogen Loss ◽

Routine Method ◽

Drying Time ◽

Sample Digestion ◽

Faecal Material ◽

Kjeldahl Method ◽

Cattle Faeces ◽

Nitrogen Contents

The effects of drying temperature and method of sample digestion on the determination of nitrogen and dry matter in the faeces of cattle grazing pastures of two different nitrogen contents were examined. Nitrogen loss varied from 8 to 20 per cent depending on the temperatures and associated length of drying time. The variation in the loss between samples from animals grazing the two pastures was small, tending to be higher for the samples taken from animals grazing a higher nitrogen pasture. Sample digestion by the H2SO4-H2O2 method was found to be as satisfactory as the micro-Kjeldahl method. Drying at 100�C for 24 hours gave the least loss of nitrogen. This procedure in conjunction with the H2SO4-H2O2 , digestion is proposed as a routine method for determination of nitrogen in faecal material.

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Automation of Methods for Meat and Meat Products. I. Determination of Protein

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/53.5.907 ◽

1970 ◽

Vol 53 (5) ◽

pp. 907-910 ◽

Cited By ~ 1

Author(s):

Jon E Mcneal ◽

Albert Karasz ◽

Elmer George

Keyword(s):

Meat Products ◽

Automated Method ◽

Kjeldahl Method ◽

Standards Development ◽

Meat Samples ◽

Selection Of

Abstract An automated method for the analysis of protein in meat was studied. The investigation included selection of proper standards, development of a method for presolubilizing meat samples for presentation to the AutoAnalyzer, and the construction of AutoAnalyzer manifolds to give protein results comparable to those obtained by the official AOAC Kjeldahl method. The method was found to be applicable to meat and meat products ranging from 5 to 25% protein.

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Manual Salicylate-Hypochlorite Procedure for Determination of Ammonia in Kjeldahl Digests

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/65.5.1076 ◽

1982 ◽

Vol 65 (5) ◽

pp. 1076-1079

Author(s):

Helen E Fukumoto ◽

George W Chang

Keyword(s):

Correlation Coefficient ◽

Spectrophotometric Method ◽

Coefficient Of Variation ◽

Precise Timing ◽

Coefficients Of Variation ◽

Moderate Volume ◽

Kjeldahl Method

Abstract The determination of nitrogen in Kjeldahl digests of urine and feces has been simplified by using a manual spectrophotometric method with salicylate and hypochlorite. It neither involves the hazards of the phenol-hypochlorite method, nor requires an automated analyzer. We determined the conditions which minimize the need for precise timing and neutralization of acidic digests and obtained coefficients of variation of about 0.8%. Agreement between the spectrophotometric method and the conventional micro-Kjeldahl method was excellent; a correlation coefficient of 0.9992 and a coefficient of variation of the estimate of 2.1% were obtained. This method is well suited for a laboratory with a moderate volume of samples. We could process at least 200 digests per day, in contrast with the 60 per day which we had previously done by the Kjeldahl distillation and titration.

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