COMPARISON OF COMBUSTION AND KJELDAHL METHODS FOR DETERMINATION OF NITROGEN IN OILSEEDS

The recent development of combustion-type nitrogen analyzers capable o f handling relatively large samples with semi-automatic operation offe rs a potential replacement for the Kjeldahl method for direct determin ation of nitrogen. Nitrogen analyses for canola seed, flaxseed, sunflo wer seed, mustard seed and soybeans on a LECO (St. Joseph, MI) FP-428 Nitrogen Analyzer were evaluated against results from the Grain Resear ch Laboratory's (GRL) Kjeldahl system. The nitrogen analyzer gave sign ificantly higher values than the Kjeldahl method, resulting in a corre ction of low values in the GRL Kjeldahl, caused by the inability to us e mercury as catalyst. The standard error for results from the analyze r was comparable to that for the Kjeldahl method. The nitrogen analyze r also was faster than the Kjeldahl method and has less environmental impact. The combustion method has replace the Kjeldahl method for rout ine nitrogen determinations in oilseed surveys conducted by the GRL.