A flow procedure is proposed for the determination of ammonium ion. The sam
ple in basic medium is forced through a solid-phase reactor containing immo
bilized 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 dev
iation (slope) 1.9 % (n = 7). The sample throughput is 48 h(-1). The influe
nce of foreign compounds is studied and the procedure is applied to ammoniu
m ion determination in pharmaceutical formulations and fertilisers. (C) 199
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