Determination of Trace Copper in Rice by Microemulsion Sensitization-Spectrophotometry

A new method to determine the trace copper in rice was established based on the sensitizing action of microemulsion(cetytrimethayl ammonium bromide,butanol,heptanol and water)in the chromogenic reaction of CAS with copper(Ⅱ).Cu2+ reacts with CAS to form a cyan complex in the NaAc-NaH2PO4 buffer solution of pH6.00 with excess amount of microemulsion with a apparent molar absorption coefficient 6.608×104L·mol-1·cm-1 at 604nm.A linear range is from 0 to 1.2mg/L with the regression equation of A=-0.01475+0.39036V,and correlation coefficient of 0.9996.The method is highly sensitive,accurate,and precise,and was applied to the determination of copper in rice with standard addition recoveries of 97%—104% and RSD=2.8%.