A flow-injection system with a AgCl(s) mini-column is proposed for the determination of total nitrogen in plant digests by flame atomic absorption spectrometry. The method is based on Ag+ removal by ammonia through the formation of the diammine argentate(I) complex and further monitoring of the released Ag+. Nitrogen was determined in seven reference samples, in three replicates, with precision and accuracy comparable to the conductimetric procedure. The system is robust, and only slight sensitivity variations (< 2 %) have been noted during extended (4 h) operating periods. Sampling rate is about 100 h-1 and measurement repeatability is fair (relative standard deviation usually < 0.02).
N-total; flow-injection analysis; atomic absorption spectrometry; mini-column