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The determination of heparin with linear sweep voltammetry has been developed in this paper based on its interaction with light green (LG). In pH 2.0 Britton -Robinson (B -R) buffer solution, LG has a sensitive linear sweep voltammetric reduction peak at À 0.41 V (vs. SCE) and heparin can react with LG to form an ion-association electroactive complex, which resulted in the decrease of the peak current of the reaction solution. Under the selected experimental conditions the decrease of peak current was directly proportional to the concentration of heparin in the range of 0.8 -20.0 mg/mL with the linear regression equation as Di '' p (nA) ¼ 79.12 C À 101.44 (n ¼ 14, g ¼ 0.996) and the detection limit as 0.28 mg/mL (3s). The effects of coexisting substances on the determination of heparin were investigated and the results showed that this method had good selectivity. The method was further applied to the determination of heparin content in heparin samples with satisfactory results and good recovery.

The interaction of phenosafranine (PSF) with a glycosaminoglycan of heparin (Hep) in aqueous solution was characterized by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in this paper and further used for Hep detection. In pH 1.5 Britton-Robinson (B-R) buffer solution PSF had a well-defined voltammetric reductive peak at -0.256 V (vs SCE), and the electrochemical response was faded by the addition of Hep. Cyclic voltammetric experiments indicated that the electrochemical behaviors of free PSF didn't change no matter whether Hep was presented in PSF solution or not. Based on the decrease of the peak current, a second order derivative linear sweep voltammetry was used to establish a sensitive electroanalytical method for Hep. The peak current was proportional to the concentration of Hep in the range of 0.7~20.0 mg L -1 , demonstrating that this method was suitable for routine Hep detection. Under optimal conditions, the linear regression equation for the Hep determination was DIp²(nA) = 46.30 C (mg L -1 ) + 343.31 (n = 11, g = 0.991) with a detection limit of 0.08 mg L -1 (3s). The established method was further successfully applied to heparin sodium injection samples determination. The interaction mechanism was discussed based on the electrostatic attraction of the negatively charged Hep with the positively charged PSF, and the stoichiometry of Hep-PSF was calculated by the voltammetric method.

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