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 x 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 ug mL-1 for Zn & 0.02-12 ug 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 ug mL-1 for Zn & 0.23 ug 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."