Micro-Determination of Protein Containing SH– and –S–S– Groups Based on the Polarographic wave of an Electroactive Derivative

Abstract.

This paper presents a new simple and sensitive method for the micro-determination of protein containing SH– and –S–S– groups based on the single sweep polarographic wave of an electroactive derivative. In 0.04 mol L⁻¹ Na₃PO₄ and 0.2% ascorbic acid solution, protein is heated in a boiling water bath for 15 min, the reaction product giving a sensitive reduction wave at −0.70 V (vs. SCE). The wave height is linearly proportional to the concentration of protein. The calibration curves of bovine serum albumin (BSA), human serum albumin (HSA), ovalbumin (OVA) and lysozyme (Lyso) are constructed under the optimal conditions. For BSA and HSA, the linear ranges and detection limits are 0.05–24 mg L⁻¹ and 0.02 mg L⁻¹, respectively. The method has been applied to the determination of protein in human serum samples with satisfactory results. The mechanism of the polarographic wave was also studied, and the results show that S²⁻ ion is released from the protein molecule during the derivatization reaction, the wave being attributed to the reduction of HgS.