Determination of Copper(II) with Acid Chrome Blue K by A_N=0 Dual-wavelength Compensation Coefficient Spectrophotometry

An AN=0 dual-wavelength compensation coefficient spectrophotometric method has been established for the determination of copper(Ⅱ) using 533 nm as the discoloring peak's wavelength.The method was based on the red dark chelate formation between copper(Ⅱ) and acid chrome blue K(ACBK) in the NaOH medium(pH=12.7).This method could determine the real absorbance of the chromogenic Cu(ACBK) through eliminating the destructive interference of discolored ACBK on Cu(ACBK) and could also determine the similar real absorbance of the ACBK through eliminating the destructive interference of Cu(ACBK) on the discoloration of ACBK.This method provided 2-fold increase in sensitivity compared with the conventional spectrophotometric methods.The compensation coefficient fs of absorbance signal is 4.135 at wavelength of λp 573 nm and λN 533 nm and the signal molar absorptivity is 4.56×104 L·moL-1·cm-1,which is 3.73 times greater than that obtained by traditional method,and the linear range is 0.02～1.60 mg·L-1 Cu(Ⅱ).The developed method has been applied for the determination of Cu(Ⅱ) in water samples with recovery in the range of 96%～104%.