A New Electrochemical Method for the Determination of Proteins with Cupferron‐Cadmium(II) Complex

A new electrochemical method was proposed for the determination of trace amounts of proteins based on the cupferron (Cup) and cadmium(II) complex Cup‐Cd(II)] as the voltammetric probe. In the selected pH 6.5 Britton–Robinson (B–R) buffer solution, Cup can interact with Cd(II) to form a stable complex of Cup‐Cd(II)], which had a sensitive linear sweep voltammetric reductive peak at ?0.654 V (vs. SCE). The addition of human serum albumin (HSA) into Cup‐Cd(II)] complex solution could greatly decrease the reductive peak current without the change of the reductive peak potential, which indicated that HSA could interact with Cup‐Cd(II)] complex to form a supramolecular biocomplex. The interaction mechanism was discussed and the decrease of reductive peak current was proportional to the concentration of HSA, which could be further used for the proteins determination. The optimal conditions of the binding reaction and the electrochemical detection were carefully investigated. Under the optimal conditions a new quantitative determination method for different kinds of proteins such as HSA, bovine serum albumin (BSA) and bovine hemoglobin (BHb) etc. was developed. The proposed method was simple, practical and relatively free from the interferences of coexisting substances, and it was further applied to the samples determination with satisfactory results. The binding constant (β_s) and the binding number (m) of HSA with Cup‐Cd(II)] complex were calculated by the voltammetric data with the results as β_s=1.12×10⁶ and m=1.