Determination of total nitrogen in sediments and plants using persulfate digestion. An evaluation and comparison with the Kjeldahl procedure

Accuracy and precision of the persulfate and Kjeldahl determinations of total nitrogen in solid samples were assessed with certified standards, plant material and river sediments. Accuracy determined with the certified reference materials was within an acceptable range to assure quality control for routine laboratory analyses. In addition, results obtained by examining plant samples indicated that TPN and TKN were not significantly different. Precision for analyses of all samples was high; however a direct comparison of plant material indicated that TPN (RSD = 5.3%) was more precise than TKN (RSD = 8.4%). TPN is a reasonable alternative to the standard TKN procedure for analysis of sediment and plant materials. The TPN method would increase the feasibility of conducting replicate analyses and would result in increased quality control.