SPECTROPHOTOMETRIC AND SIMULTANEOUS DERIVATIVE SPECTROPHOTOMETRIC DETERMINATION OF GOLD(III) AND SILVER(I) WITH RHODANINE DERIVATIVE IN MICELLAR MEDIUM

The determination methods of the gold(III) and silver(I) with, 5-(4-hydroxy-3-methoxybenzylidene) rhodanine (3,4-MHBR) in the presence of benzyldimethyltetradecylammonium chloride (zephiramine), and 5-(3,4-dihydroxybenzylidene) rhodanine (3,4-DHBR) in the presence of cetyltrimethylammonium bromide (CTAB) have been described. The application of first- and second-derivative spectrophotometry to simultaneous determination of gold(III) and silver(I) in their mixtures have been assayed using ''zero-crossing'' technique of measurement. In the pH ranges 8.8-9.8 and 9.0-10.2 the ternary 1:3:3 and 1:2:2 complexes gold(III)-3,4-MHBR-zephiramine and silver(I)-3,4-MHBR-zephiramine have been formed with molar absorptivities of 4.98x10(4) and 4.64x10(4) dm(3) mol(-1) cm(-1) at 529 and 522 nm, respectively. The ternary 1:3:4 and 1:2:3 complexes gold(III)-3,4-DHBR-CTAB and silver(I)-3,4-DHBR-CTAB have been formed in the pH ranges 9.4-10.2 and 9.0-10.5 with molar absorptivities of 8.63x10(4) and 7.76x10(4) dm(3) mol(-1) cm(-1) at 560 and 555 nm, respectively. The first- and second-derivative spectra of these complexes allow the determination of one metal in the presence an excess of the other. Gold(III) (0.21-3.6 mu g cm(-3)) and silver(I) (0.12-2.63 mu g cm(-3)) in different ratios have been determined simultaneously with good precision and accuracy using the proposed methods. The statistical analysis of the experimental results are presented. The methods have been applied to simultaneous determination of gold and silver in silicate rocks.