Fourth Derivative Spectrophotometric Determination of Trace Silver after Preconcentration with the Ion Pair of 2-Nitroso-1-naphthol-4-sulfonic Acid and Tetradecyldimethylbenzylammonium Chloride by Microcrystalline Naphthalene or Column Method

Sa？etak Silver is quantitatively retained as 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S) and tetradecyldimethylbenzylammonium (TDBA) ion associated complex on microcrystalline naphthalene in the pH range 9.5-11.0 from large volumes of its aqueous Solutions of various alloys and biological samples. After filtration, the solid mass consisting of metal complex and microcrystalline naphthalene was dissolved in dimethylformamide (DMF) and the metal determined by fourth derivative spectrophotometry. Silver can alternatively be quantitatively adsorbed on (nitroso-S)-(TDBA)-naphthalene adsorbent packed in a column at a flow rate of 1-2 ml min-1 and determined similarly. The calibration curve is linear over the concentration range 0.2-30 pg ml-1 of silver in dimethylformamide solution by measuring the distance d4A/cU4 between (606 nm) and (562 nm) with a correlation coefficient of 0.9994 and relative standard deviation of ±1.1%. The analytical sensitivity is calculated to be 0.198(d4A/dA4)/ pg ml-1 from the slope of the calibration curve. The detection limit is 0.15 pg ml-1 for silver at the minimum instrumental settings (signal to noise ratio = 2). Various parameters such as the effect of pH, volume of aqueous phase and interference of a large number of metal ions on the determination of silver have been studied in detail to optimize the conditions for its determination in various complex samples