Determination of trace amounts of mercury(II) in water samples using a novel kinetic catalytic ligand substitution reaction of hexacyanoruthenate(II).

A simple, sensitive, selective and rapid kinetic catalytic method has been developed for the determination of Hg(II) ions at micro-level. This method is based on the catalytic effect of Hg(II) ion on the rate of substitution of cyanide in hexacyanoruthenate(II) with nitroso-R-salt (NRS) in aqueous medium and provides good accuracy and precision. The concentration of Hg(II) catalyst varied from 4.0 to 10.0x10(-6)M and the progress of reaction was followed spectrophotometrically at 525nm (lambda(max) of purple-red complex Ru(CN)(5)NRS, epsilon=3.1x10(3)M(-1)s(-1)) under the optimized reaction conditions; 8.75x10(-5)M [Ru(CN)(6)(4-)], 3.50x10(-4)M [nitroso-R-salt], pH 7.00+/-0.02, ionic strength, I=0.1M (KCl), temp 45.0+/-0.1 degrees C. The linear calibration curves, i.e. calibration equations between the absorbance at fixed times (t=15, 20 and 25min) versus concentration of Hg(II) ions were established under the optimized experimental conditions. The detection limit was found to be 1.0x10(-7)M of Hg(II). The effect of various foreign ions on the proposed method has also been studied and discussed. The method has been applied to the determination of mercury(II) in aqueous solutions.