Determination of zinc ions in water samples and pharmaceutical preparations

A spectrophotometric technique was adopted for the determination of zinc ions through coordination with 4-[2-pyridylazo]-1-naphthol [p- PAN] at pH 2.5 and formation of dark red color. Beer's law was obeyed in the concentration range of 2 to 40 mug zinc ions per 25 ml with maximum absorbance at 550 nm and molar absorptivity of 9.5 x 10 6 L mol -1 cm -1. Zinc ions were also determined amperometrically at an applied potential of +0.75 volt to the graphite electrode using st and ard solution of p-PAN in the concentration range of 1 x 10 -3 to 1 x 10 -6 M solution. Both procedures were applied for the determination of zinc ions in some water samples of Egypt and in pharmaceutical preparations