Comparison of Dumas and Kjeldahl methods with automatic analyzers on agricultural samples under routine rapid analysis conditions

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Abstract
With the improvement in dry combustion nitrogen (N) analyzer technology and because of the expense of disposing of hazardous laboratory waste chemicals, the Dumas method is replacing the traditional Kjeldahl method as the method of choice for N analysis. Consequently, comparison of the Dumas method with the Kjeldahl method is important. Typically such comparisons have been done on small numbers of distinctive samples. The objective of this research was to evaluate the performance of instruments which use automated Dumas (Macro-N) and Kjeldahl (KjelFoss) methods for N analysis of agricultural materials in a routine high-throughput laboratory situation. Samples of manure, sewage sludge, plant tissue, plant seeds, and fibers of feedstuffs were analyzed for N concentrations using both instruments. The statistics of the N concentrations were evaluated for all samples as a group and as specific sub-populations. The N results from the all-samples population rendered a simple linear correlation coefficient of 0.9...