Spectrophotometric Determination of Heparin Sodium Salt by Decoloration of Night Blue

Based on the color-fading of night blue by its strong interaction with heparin in an acetate buffer solution of pH 4.5,a spectrophotometric method for determination of heparin was proposed.Experimental conditions,including the values of pH of the reaction system,amount of night blue and time of reaction were tested and optimized,and mechanism of the reaction was also discussed.The magnitude of decrease in absorbance (ΔA) was found to keep linear relationship with mass concentration of heparin in the range within 2.0 mg·L-1 as measured at its absorption maximum of 618 nm.The proposed method was used in the analysis of sodium heparin injections,giving values of recovery found by standard addition method in the range of 100.3%-101.0%.