NEW SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF TRACE LEVEL OF SILVER USING 2,2'-DI(2,3,4-TRIHYDROXYPHENILAZO)BIPHENYL

A very simple, sensitive, highly selective and non-extractive spectrophotometric method for the determination of trace amounts of silver(I) has been developed. 2,2'-di(2,3,4-trihydroxyphenilazo)biphenil (DTFAB) has been proposed as a new analytical reagent for the direct non-extractive spectrophotometric determination of silver(I). In the water media DTFAB reacts with silver to give a highly absorbent greenish yellow chelate with a molar ratio 2:1 (Ag:DTFAB). The reaction was instantaneous and the maximum absorption was obtained at 540 nm and remains stable for 24 h. The average molar absorptivity and Sandell's sensitivity were found to be 4.3•104 l mol-1 cm-1 and 5.0 mkg/cm2 of silver(I), respectively. Linear calibration graphs were obtained for 0.1–30 mkg/ml of silver(I). A large excess of over 30 cations, anions and complexing agents do not interfere in the determination. The method is highly selective for silver and was successfully applied to synthetic mixtures. The method has high precision and accuracy (s = ± 0.01 for 0.5 mkg/l)