An acid dichromate digestion procedure for total nitrogen determination in soils

2000 ◽  
Vol 31 (3-4) ◽  
pp. 521-527 ◽  
Author(s):  
K.L. Sahrawat ◽  
K.V.S. Murthy
Keyword(s):  
Total Nitrogen ◽  
Digestion Procedure ◽  
Nitrogen Determination

Total Nitrogen Determination of Various Sample Types: A Comparison of the Hach, Kjeltec, and Kjeldahl Methods

1987 ◽  
Vol 70 (3) ◽  
pp. 410-412
Author(s):  
Kevin L Watkins ◽  
Trygve L Veum ◽  
Gary F Krause
Keyword(s):  
Total Nitrogen ◽  
Sample Type ◽  
N Content ◽  
Nitrogen Determination ◽  
N Sources ◽  
Wide Range ◽  
Determination Methods ◽  
The Mean ◽  
Intermediate Results

Abstract Conventional Kjeldahl analysis with modifications, Kjeltec analysis with block digestion and semiautomated distillation, and the Hach method for determining nitrogen (N) were compared using a wide range of samples. Twenty different sample types were ground and mixed. Each sample type was divided into 5 subsamples which were analyzed for N by each of the 3 methods. In each sample type, differences (P < 0.05) were detected among the 3 N determination methods in 5 of the 20 N sources analyzed. The mean N content over all 20 samples was higher with Kjeldahl analysis (P < 0.05) than with Kjeltec, while Hach analysis produced intermediate results. Results also indicated that the Hach procedure had the greatest ability to detect differences in N content among sample types, being more sensitive than either other method (P < 0.05).

Direct and Indirect Determination of True Protein Content of Milk by Kjeldahl Analysis: Collaborative Study

1991 ◽  
Vol 74 (2) ◽  
pp. 281-288 ◽  
Author(s):  
David M Barbano ◽  
Joanna M Lynch ◽  
J Richard Fleming
Keyword(s):  
Nitrogen Content ◽  
Protein Content ◽  
Total Nitrogen ◽  
Collaborative Study ◽  
Total Nitrogen Content ◽  
Nonprotein Nitrogen ◽  
Protein Nitrogen ◽  
Nitrogen Determination ◽  
True Protein

Abstract Currently, the reference procedure for determination of the "protein" content of milk is based on measurement of the total nitrogen content of milk by the Kjeldahl method (AOAC method, 920.105). About 6% of the total nitrogen content of milk Is nonprotein nitrogen. Therefore, total nitrogen multiplied by the conversion factor 6.38 overestimates the true protein content of milk on average by about 6%. In the present study, new direct and Indirect methods were developed for measurement of the true protein content of whole milk by Kjeldahl nitrogen determination. Both new methods are sample preparation procedures used to fractionate the nitrogen-containing compounds In milk prior to measurement of the nitrogen content of these fractions by Kjeldahl analysis. The collaborative study consisted of 9 pairs of blind duplicate milk samples that were analyzed for total nitrogen, nonprotein nitrogen, and protein nitrogen by each of 10 laboratories. Both methods for true protein measurement (direct and Indirect) gave acceptable statistical performance characteristics and good agreement between methods. The new direct method requires about half the laboratory analysis work of the indirect method (i.e., total minus nonprotein nitrogen). The methods have been adopted official first action by AOAC as (1) a new method for nonprotein nitrogen determination in milk, (2) a new method (direct) for determination of protein nitrogen content of milk, and {3) an alternative method (indirect) for determination of protein nitrogen content of milk.

Zirconium Dioxide, A New Catalyst, in the Kjeldahl Method for Total Nitrogen Determination

1974 ◽  
Vol 57 (5) ◽  
pp. 1228-1230 ◽  
Author(s):  
William Glowa
Keyword(s):  
Total Nitrogen ◽  
Zirconium Dioxide ◽  
Mercuric Oxide ◽  
Cupric Sulfate ◽  
Nitrogen Determination ◽  
Mixed Catalyst ◽  
Kjeldahl Method

Abstract The standard Kjeldahl method for the determination of total nitrogen in fertilizers, feeds, foods, and beverages has been modified to eliminate the use of mercuric oxide, which is poisonous to the environment. A new mixed catalyst, consisting of 0.60 g cupric sulfate and 0.20 g zirconium dioxide in combination or 0.70 g zirconium dioxide alone, is recommended to replace the 0.70 g or more of mercuric oxide used in all official macro Kjeldahl methods.

Tellurium as Catalyst in Semimicro Kjeldahl Method for Total Nitrogen Determination

1982 ◽  
Vol 65 (4) ◽  
pp. 786-790
Author(s):  
Christina F-H Liao
Keyword(s):  
Total Nitrogen ◽  
Organic Nitrogen ◽  
Complete Recovery ◽  
Nitrogen Compounds ◽  
Nitrogen Determination ◽  
Plant Soil ◽  
Clearing Time ◽  
Kjeldahl Digestion ◽  
Kjeldahl Method ◽  
Agricultural Materials

Abstract A modified semimicro Kjeldahl procedure is described for total nitrogen determination in agricultural materials and refractory organic nitrogen compounds, in which tellurium, alone or in combination with copper, is used as a catalyst. Tellurium alone is adequate for complete recovery of nitrogen from nicotinic acid if the acid:salt ratio is carefully controlled to nearly 1. However, when a mixture of tellurium and copper is used, complete nitrogen recovery could be obtained at a higher acidrsalt ratio. Use of a mixture also reduces clearing time when compared with copper alone in the Kjeldahl digestion. For samples containing nitrate, a Devarda's alloy (Cu:Al:Zn = 10:9:1) is proposed as a reducing agent in the pretreatment procedure to convert nitrate to ammonium in 6N H2SO4, with subsequent digestion of the sample by using a mixture of K2S04-catalyst and concentrated H2SO4. The proposed method is applicable for total nitrogen determination including NO3-N in plant, soil, and fertilizer samples.

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