Photometric Determination of Copper in Rice with Dibromo-p-Chloro-Chlorophosphonazo

The color reaction of copper(Ⅱ) with 2,6-dibromo-4-chloro-benzene chlorophosphonazo (CPA-DBC) was studied.In a buffer medium of HOAc-NaOAc at pH 4.7,copper(Ⅱ) reacts with CPA-DBC to form a blue-violet complex with a molar ratio (M∶R) of 1∶2,and a molar absorptivity of 2.3×104L·mol-1·cm-1 at its absorption maxima at 606 nm.Beer′s law is obeyed over the range of 0-25 μg of Cu(Ⅱ) in 25 mL of solution.The effect of 31 coexisting ions was tested.In its application to the determination of copper in rice,RSD′s (n=6) found were less than 2%,and the values of recovery test obtained by the standard addition method were in the range of 96.6%-98.7%.