Catalytic-Kinetic Determination of Silver(I) Using Hexacyanoferrate(II) and 2,4,6-Tripyridyl-1,3,5-Triazine(TPTZ)

A highly sensitive and selective kinetic spectrophotometric method is proposed for the determination of silver in nanogram quantities. The method is based on catalytic activity of silver(I) in enhancing the green colour formation between potassium ferrocyanide and 2,4,6-tripyridyl-1,3,5-triazine (TPTZ) which is otherwise a very slow reaction at pH 2.0. The absorbance spectrum of the green coloured solution in presence of silver showed two peaks of almost equal intensity one at 405 nm and another at 600 nm. At both the wavelengths the absorbance of the experimental solution increased proportionally with the amount of silver(I) in the range 5 – 410 ng mL^-1 and 10 – 610 ng mL^-1 respectively. Other experimental conditions like pH, reagent concentration, ferrocyanide concentration and effect of time for obtaining maximum reaction rate were optimized. The molar absorptivity, Sandell's sensitivity, detection limit, determination limit and relative standard deviation (n = 8) were determined as 1.57 × 106 L mol^-1 cm^-1, 0.065 ng cm^-2, 1.6 ng mL^-1, 4.8 ng mL^-1 and 0.81 % respectively. The effect of various diverse ions on the determination of silver was studied. The method was applied for the determination of silver in alloys, biological samples, effluents, real water and in ayurvedic medicines.