Milk and milk products. Determination of nitrogen content and crude protein calculation. Kjeldahl method

2008 ◽  
Keyword(s):  
Nitrogen Content ◽  
Crude Protein ◽  
Milk Products ◽  
Kjeldahl Method

Comparison of Kjeldahl and the Elemental Analysis Methods for Determination of Nitrogen Content in Raw Natural Rubber

2013 ◽  
Vol 815 ◽  
pp. 722-726 ◽  
Author(s):  
Ning Li Qi ◽  
Pu Wang Li ◽  
Xian Hai Zeng ◽  
Hong Hai Huang ◽  
Zi Ming Yang ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Nitrogen Content ◽  
Elemental Analysis ◽  
Linear Correlation ◽  
Crude Protein ◽  
Analysis Method ◽  
Analysis Methods ◽  
Significant Difference ◽  
Kjeldahl Method

The nitrogen in raw natural rubber is mainly derived from crude protein of latex. In this study, the nitrogen content of six kinds of raw natural rubber was analyzed for evaluating Kjeldahl and elemental analysis methods. The nitrogen content ranged from 0.43% to 0.66% for Kjeldahl methods and from 0.45% to 0.75% for elemental analysis method. There was no significant difference between the two methods. The coefficient of variation was below 1%. The data of nitrogen content showed a simple linear correlation (r=0.9937) between the two methods. It was concluded that the elemental analysis method could replace Kjeldahl method in nitrogen analysis of raw natural rubber.

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

1989 ◽  
Vol 72 (5) ◽  
pp. 770-774 ◽  
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.

Determination of Nitrogen Content in Milk by the Kjeldahl Method Using Copper Sulfate: Interlaboratory Study

1988 ◽  
Vol 71 (5) ◽  
pp. 893-898 ◽  
Author(s):  
R Grappin ◽  
William Horwitz
Keyword(s):  
Quality Control ◽  
Nitrogen Content ◽  
Copper Sulfate ◽  
Interlaboratory Study ◽  
Internal Quality ◽  
Relative Standard ◽  
Nitrogen Concentrations ◽  
Kjeldahl Method ◽  
Repeatability And Reproducibility

Abstract Copper sulfate was substituted for mercury as the catalyst in the International Dairy Federation (IDF) Standard 20A:1986 method for the determination of nitrogen content in milk. The substitution was supported by results obtained in an interlaboratory study by 24 laboratories in 12 countries. Each laboratory analyzed 12 test samples of milk as blind duplicates in a double split level design with high, medium, and low nitrogen concentrations. The method protocol requires the concurrent analyses of an ammonium salt solution and a tryptophan solution as internal quality control standards with a minimum nitrogen recovery between 99 and 100% for the former and at least 98% for the latter. The repeatability and reproducibility relative standard deviations are 0.5 and 1%, respectively, for the range 0.35-0.70 g N/100 g. The performance of the laboratories that did not meet the required quality control specifications was clearly poorer than that of those that did meet the specifications.

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