Determination of Total Nitrogen in Plant Material¹

TLDR

The study presents a simple, precise method for estimating total nitrogen in plant tissue, including a modification for high‑nitrate samples. Plant tissues are digested in pyrex Folin‑Wu tubes using a salt‑catalyst‑sulfuric acid mixture, heated in an aluminum block to boiling for 60 min after clearing. The method produced total N values comparable to standard AOAC procedures, with a coefficient of variation of 0.87–1.10%, and enables simultaneous digestion of 60 samples, greatly improving efficiency.

Abstract

Abstract A simple and precise procedure for estimating total N in plant tissue is described; a modification is also described for analysis of samples containing high nitrate concentrations. Plant tissue samples are placed in pyrex Folin‐Wu tubes and digested with a salt‐catalyst‐sulfuric acid mixture by heating the tubes in an aluminum block. Samples are digested at the boiling point of the mixture for 60 min after initial clearing of the digests. Analyses of diverse plant materials, containing from 0.006 to 0.3% NO 3 ‐N 3 indicated that the proposed and standard AOAC procedures yielded essentially the same total N values. The coefficient of variation for the proposed methods varied from 0.87 to 1.10%. The tube digestion procedures described allows digestion of 60 plant samples simultaneously and thus greatly improve the efficiency of total N determinations.