Comparison of Kjeldahl and Dumas combustion methods for determination of nitrogen content in animal manures

In order to compare the determination features nitrogen content in animal manures by Dumas combustion method and Kjeldahl methods, five kinds of manures and one reference compound were analyzed for nitrogen concentrations using Kjeldahl and Dumas combustion procedures respectively. Statistical analysis was performed on Kjeldahl nitrogen and Dumas nitrogen values. The results showed that the Kjeldahl nitrogen content of animal manures ranged from 0.51% to 3.19% and the Dumas combustion nitrogen content ranged from 0.51% to 3.35%, there was no significant difference in the nitrogen mean values measured by the two methods, and the coefficient of variation of two methods were all below 5%. The nitrogen determined results from the all-samples population rendered a simple linear correlation (R2=0.987, p<0.05) between the two methods. All the Kjeldahl values as a function of Dumas values was close to 1:1 line. It was concluded that the Dumas combustion procedure is capable of replacing the Kjeldahl procedure for nitrogen analysis of animal manures in laboratory.