Determination of trace copper in serum by a new catalytic kinetic spectrophotometric method

A new catalytic kinetic method based on the decolorization reaction of rhodamine B has been established for the determination of copper in serum. In the presence of copper, rhodamine B can be oxidized by hydrogen peroxide in the NH3-NH4F medium. After each serum sample was digested with strong acid, the catalytic reaction was carried out in NH3-NH4F buffer (pH9.0) at 100 degrees C for 17 min (1.0 ml buffer, 2.0 ml rhodamine B, 1.2 ml H2O2 for a 25 ml reaction mixture). Copper concentration and log A(0)/A are linearly related over the concentration range of 20-140 ng/25 ml (r = 0.9999, y = 0.003387x - 0.05969). Repeated assay of a mixture normal serum sample gave CVs of 5.2% (n = 14). The mean recoveries were 98.3%, 101.2%, and 100.2% for three different serum samples. Ca, Mg, Fe, Zn, Na, K, Cl, P, and other elements in serum did not interfere with the determination. The concentrations of copper were 75-170 mu g/100ml in serum of 30 normal volunteers; the mean concentration was 115.4 mu g/100ml. (C) 1996 Academic Press, Inc.