Flow spectrophotometric determination of ammonium ion Original Research Article

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 μg ml−1 ammonium ion, detection limit (s/n = 3)  0.35 μg 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.