Simultaneous Determination of 4 Kinds of Residual Organic Solvents in Clobetasol Propionate by Capillary Gas Chromatography

OBJECTIVE:To establish the method for the content determination of 4 kinds of residual organic solvents(methanol,ethanol,N,N-dimethylformamide,dimethylsulfoxide) in clobetasol propionate. METHODS:The residual solvents in beclometasone dipropionate were separated on HP-INNOWAX capillary column. 1,6-dioxane was used as solvent. The carried gas was nitrogen at flow rate of 1.0 mL·min-1. The programmed column temperature was set as follows:maintained at 60 ℃ for 5 min and raised to 160 ℃ at the rate of 30 ℃·min-1 followed by holding for 5 min. The injector temperature and FID detector temperature were controlled at 160 ℃ and 250 ℃,respectively. The splitting-ratio was 5.0 ∶ 1. Hydrogen was use as fuel gas at flow rate of 30 mL·min-1 with air as combustion-supporting gas at flow rate of 450 mL·min-1. The makeup gas was nitrogen at flow rate of 25 mL·min-1. The injection volume was 1 μL. The contents of 4 kinds of residual solvents in 5 batches of samples were determined under same condition. RESULTS:Methanol,ethanol,N,N-dimethylformamide,dimethylsulfoxide in clobetasol propionate were completely separated. The linear ranges were 0.02-1.0 g·L-1(r=1.000) . Average recovery rates were 97.6%-102.5%(RSD2.88%) . The minimum quantitative concentrations were 0.60 μg·mL-1,0.98 μg·mL-1,0.38 μg·mL-1,0.85 μg·mL-1,respectively. Methanol was found in 1 batch of sample and ethanol was found in 2 batches of samples. No organic solvent was found in other batches of samples. CONCLUSIONS:The established method is proved to be accurate and sensitive. It can be used for simultaneous determination of 4 kinds of residual organic solvents in clobetasol dipropionate.