Simultaneous determination of copper and cadmium as Cu(DDTC) 2 Spectrophotometrically after fractional extraction

Copper(II) and cadmium(II) forms M(DDTC) 2 complexes (M=Cu, Cd) with diethyldithiocarbamate (DDTC) that is extracted in CHCl 3 /CCl 4 . Yellow Cu(DDTC) 2 shows maximum absorbance at 435 nm whereas Cd(DDTC) 2 has no absorption. Extract was divided into two fractions. Absorption of one fraction is directly measured which is equivalent to Cu(II) present in sample. Addition of excess copper(II) to the second fraction of the extract displaces cadmium quantitatively forming additional Cu(DDTC) 2 as its stability is higher than Cd(DDTC) 2 . The absorbance of second extract is measured subsequently when additional absorbance is equivalent to cadmium. Linear calibration range was obtained 0.05–17 µg mL -1 for cadmium and 0.02–12 µg mL -1 for copper with the regression coefficient (r 2 ) 0.998 for each. In the presence of EDTA as masking agent very good selectivity was achieved.