Simultaneous Determination Of Zn And Cu : Spectrophotometric measurement of Cu(DDTC)2 for the simultaneous determination of Zinc and Copper

A simple spectrophotometric method is presented for the rapid determination of Zn using diethyldithiocarbamate(DDTC) as a new spectrophotometric reagent in a acidic (0.001 M H2SO4) aq. solution. Complex formed by Cu with DDTC is more stable than Zn. The method is based on the quantitative replacement of Zn(II) with Cu(II) from its DDTC-complex and subsequent measurement of Cu(DDTC)2 at 435 nm (max). Therefore, simultaneous determination of both Cu and Zn has been proposed. The average molar absorptivity of the method for Zn determination was found to be 2.86 105 L. mol.-1 cm.-1. The reaction is instantaneous & the absorbance remains stable for over 72 h. The Sandell's sensitivity was found to 3.076 ng cm-2 of Zn. Linear calibration range was obtained of 0.02-14 g mL-1 for Zn & 0.02-12 g mL-1 for Cu. The stoichiometric composition of chelate is 1:2 (Zn/Cu : DDTC). The method is characterized by a detection limit of 0.29 g mL-1 for Zn & 0.23 g mL-1 for Cu. Large excess of over 50 cations, anions & complexing agents do not interfere in the determination. The method was successfully applied to a number of environmental, biological, food, pharmaceutical & fertilizer samples.