Linear Sweep Polarographic Determination of Chondroitin Sulfate with Toluidine Blue as Electrochemical Probe
Sun Wei, Zhao Na, Xu Xiao, Jiao Kui(College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042)
An electrochemical study on the interaction between chondroitin sulfate (CS) and toluidine blue (TB) using a mercury-working electrode in pH 5.0 Britton-Robinson (B-R) buffer solution was carried out. TB had a well-defined second order derivative linear-sweep polarographic wave at -0.04 V. Adding CS to the TB solution resulted in the decrease of the peak current without shift of the peak potential, which indicated that a supramolecular complex was formed and resulted in the decrease of the diffusion coefficient. The conditions of binding reaction and electrochemical detection were optimized. Based on the decrease of the reductive peak current, a new electrochemical method for CS quantitation was developed with the linear range of 6.0-30.0 mg/L and the linear regression equation of Ip″(nA) =92.96C (mg/L)-500.36 (n=16,r=0.9909). The established method was applied to the analysis of synthetic samples with satisfactory results. The binding constant (βs) and the binding number (m) of CS with TB were calculated by the voltammetric data with the results of βs= 2.57×1010 and m= 2.