Speciation analysis of serum copper by ultrafiltration combined with graphite furnace atomic absorption spectrometry

Ultrafiltration combined with graphite furnace atomic absorption spectromet ry (GFAAS) was used to study protein binding and speciation of copper in hu man serum. Ultrafiltration was carried out using a cell unit with ultrafilt ration membranes having a nominal cut-off of 10,000 Dalton. The effects of various experimental factors including the kind and concentration of electr olyte, sample storage, pH, pressure and the preconditioning of the membrane s on the speciation analysis of serum copper by ultrafiltration were examin ed. It was observed that 4.5 +/- 2.3% of the total copper in serum was ultr afiltrable and this value did not seem to be influenced by the total serum elemental concentration, the pH (6.5 - 10) and the pressure (I 1.5 kg/cm(2) ). The preconditioning of the ultrafiltration system with 0.1 mol/L calcium nitrate can overcome the adsorption loss of copper effectively, and the ad dition of tris-HCl solution (pH 7.4) to serum accelerates the ultrafiltrati on. The present method was proved to be suitable for speciation analysis fo r its simplicity, rapidity, small sample requirement and easy control. The results obtained with the method are accurate and reliable.