UV-Spectrophotometric Determination of Glucosamine Hydrochloride in Its Drug Capsule

Based on the phenomenon of coordination of glucosamine hydrochloride (GSM) with Ni²⁺ in alkaline medium to form a coordination complex having its absorption maximum at 219 nm, further research was done to work out a method for UV-spectrophotometric determination of GSM in its drug capsule. In the determination, the drug particles of GSM in a capsule were taken, weighed (ca. 0.24 g as labelled), dissolved and made its volume to 250 mL with water. An aliquot of 5.00 mL of this solution was taken and placed in a 50 mL volumetric flask, 10 mL of 0.10 mol·L^-1 sodium hydroxide solution and 2.00 mL of 1.0×10^-2mol·L^-1 nickel sulfate solution were added successively and volume of the solution was made up to 50 mL with 0.10 mol·L^-1 sodium hydroxide solution. Then the solution was placed into a water bath keeping at constant temperature of 20℃ for 15 min for completion of the coordination reaction. Absorbance of the solution was then measured at 219 nm. Linear relationship between values of absorbance measured and the respective concentrations of GSM was obtained in the range from 6.00×10^-4 to 4.00×10^-3mol·L^-1; the detection limit (3S/N) found was 4.10×10^-5mol·L^-1. On the base of GSM taken from a capsule, recovery was tested by addition of GSM standard solution at 4 concentration levels, giving results of recovery in the range of 80.0%-110% and values of RSDs (n=5) less than 0.2%. A substantial drug capsule was analyzed by this method, the concentration of GSM found was 7.26×10^-4mol·L^-1, which was equivalent to a mass of 0.238 6 g in the capsule by conversion calculation. This value was found in consistency with the labelled value.