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

Abstract

AbstractA 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 (βs) and the binding number (m) of HSA with [Cup‐Cd(II)] complex were calculated by the voltammetric data with the results as βs=1.12×106 and m=1.