Determination of trace copper in steel samples with copper-thiocyanate-ethyl violet-microemulsion spectrophotometry

Copper and thiocyanate can form a complex anion [Cu(SCN)4]2-.Then ethyl violet forms an adsorption ion-association complex with [Cu(SCN)4]2-in pH 3.6 acetate buffer solution by using the nonionic(O/w) microemulsion(OP/n-C5H11OH/n-C7H16/H2O).The composition ratio of [Cu(SCN)4]2-to ethyl violet is 1:2.The maximum absorption wavelength of the ion-association complex is 660 nm.The apparent molar absorption coefficient is 1.08×l05 L·mol-1·cm-1.Beer′s law is obeyed in the concentration rang of 1.7-18.0 μg/50 mL for copper.The detection limit is 0.5 μg/50 mL.The method is applied to the determination of copper in the steel samples,the relative standard deviation is less than 2%,and the results are satisfactory.