Determination of sulfur in topical formulations by GC-MS

A new method has been developed for the determination of sulfur in topical formulations by GC-MS. The separation of the sulfur was achieved on a TR-5MS, 30m, 0.25mmID, 0.25µm column with a mobile phase containing helium at a flow rate of 1 mL/min. The column temperature is 190°C and the total run time is 13 min. The sulfur was detected at 64 m/z with selective ion mode. The injection volume was 1 μL. The assay was in for sulfur the concentration ranges from 10–15 µg/mL. LLOQs (µg/mL) and LLODs (µg/mL) 0.75 and 0.25 for sulfur. Recoveries of the sulfur were between 95% and 105% with intra-and inter-day precisions (as relative standard deviation) of ≤2%. Method validation was carried out according to ICH guideline Q2 (R1). Also, the uncertainty measurement study of the method developed for the determination of sulfur in topical formulations was carried out. The analytical method validated was successfully applied to topical formulations.