Flow spectrophotometric determination of ammonium ion

A flow procedure is proposed for the determination of ammonium ion. The sample in basic medium is forced through a solid-phase reactor containing immobilized AgCl on polymeric pearl beads. The released Ag+, complexed with the ammonia, gives a blue ternary complex with the aid of bromopyrogallol red and 1,10-phenanthroline which is spectrophotometrically monitored at 636 nm. The calibration graph is linear over the range 1-20 mu g ml(-1) ammonium ion, detection limit (s/n = 3) = 0.35 mu g ml(-1) and relative standard deviation (slope) 1.9 % (n = 7). The sample throughput is 48 h(-1). The influence of foreign compounds is studied and the procedure is applied to ammonium ion determination in pharmaceutical formulations and fertilisers. (C) 1999 Elsevier Science B.V. All rights reserved.