DUAL-WAVELENGTH SPECTROPHOTOMETRIC DETERMINATIONS OF COPPER AND ITS COMPOSITION OF THE COMPLEX WITH ERIOCHROME BLUE BLACK R

Copper has been determined by a modified dual-wavelength spectrophotom etric (DWS) method, using the reaction of Cu(II) with eriochrome blue black R (EBBR) at pH 12, which is sensitive and selective in the prese nce of both pentadecyltrimethylammonium bromide (PTMAB) and ascorbic a cid. The modified DWS can completely eliminate the effect of excess EB BR in its Cu(II) solution and give the real absorbance of the produced chelate of Cu(II) with EBBR, with increased analytical sensitivity an d decreased error. The composition of the complex of Cu(II) with EBBR can be determined easily and accuratively. Beer's law is obeyed over t he concentration range of 0-1.60 mg Cu per 1 and the true molar absorb ance of chelate Cu(EBBR)2 at 550 nm has been computed as 1.80 . 10(4) . mol-1 . cm-1. The detection limit of Cu is 0.04 mg. This method has been applied for the determination of trace amounts of copper in waste water with satisfactory results.