Rapid determination of trace copper in powdered drinks by EDTA titrimetry

Trace copper in powdered drinks is determined by the EDTA titrimetry.First,the samples are wetly digested by HNO3-HClO4.Then,in one wetly digested sample,with XO as the indicator,the total amount of metallic ions is determined with the standard solution of EDTA while the pH is 5 ～ 6.And in another wetly digested sample,thiourea is added to mask Cu2+,then metallic ions other than Cu2+ are determined with the standard solution of EDTA.The difference between the two results is the amount of copper.The RSD% is 0.48% and R is between 98.8% and 100.6%.