CATALYTIC DETERMINATION OF SILVER(I) BY EXTRACTIVE FLOW-INJECTION ANALYSIS

A new catalytic method for the determination of silver(I) was develope d based on a metal exchange reaction between ethylenediaminetetraaceta tomercury(II) (Hg-II - EDTA) in the aqueous phase and bis(diethyldithi ocarbamato)copper(II) (Cu-II - DDTC) in the organic phase. This exchan ge reaction (Cu-II - DDTCorg + Hg-II-EDTA --> Hg-II - DDTCorg + Cu-II - EDTA, where org denotes the organic phase) was observed to proceed s lowly and the Cu-II - DDTC complex transferred quantitatively to Hg-II - complex in the organic phase in the equilibrium state. In this syst em, silver(I) acts as the catalyst and can be determined by measuring the decrease in the absorbance of the Cu-II - DDTC complex (lambda(max ) = 435 nm). The reaction was applied to the extractive flow injection analysis of silver(I). The present method allows the determination of silver(I) at 10(-7) mol dm(-3) level with the sampling frequency of 3 0 h(-1). The relative standard deviation of 0.28% (n = 10) was obtaine d at 4.0 x 10(-7) mol dm(-3) of silver(I). (C) 1998 Elsevier Science B .V.