Determination of human serum albumin using aurothiomalate as electroactive label

A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I) bound to the anti-HSA was electrodeposited in 0.1 mol L-1 HCl at -1.00 V for 5 min then oxidised in 0.1 mol L-1 H2SO4 solution at +1.40 V for 1 min. Silver electrodeposition at -0.14 V for 1 min followed by anodic stripping voltammetry were then performed in aqueous 1.0 mol L-1 NH3-2.0x10(-4) mol L-1 AgNO3. For both non-competitive and competitive formats, calibration plots in the ranges 5.0x10(-10) to 1.0x10(-8) mol L-1 and 1.0x10(-10) to 1.0x10(-9) mol L-1 HSA, respectively, with estimated detection limits of 1.5x10(-10) mol L-1 (10 ng mL(-1)) and 1.0x10(-10) mol L-1 (7 ng mL(-1)), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay formats.