Spectrophotometric determinationof zinc in cooking salts,tap and mineral waters with phenylglyoxal mono(2-pyridyl)hydrazone

The behaviour of phynylglyoxal mono(2-pyridyl)hydrazone (PGMPH) with various metal ions was studied by spectrophotometry. The reaction of zinc with PGMPH provides a sensitive and precise method for the determination of zinc in tap and mineral waters and in cooking salts. Zinc ion reacts with PGMPH at pH 7.2—8.5 in solutions containing 40% (v/v) ethanol to form a yellow-orange complex with maximum absorbance at 464—470 nm. The molar absorptivity of the 1:2 ZnPGMPH complex is 71 300 1 mol^?1 cm^?1. Interferences are considered in detail.