Determination of diclofenac sodium, flufenamic acid, indomethacin and ketoprofen by LC-APCI-MS

A sensitive, selective and accurate high-performance liquid chromatography- mass spectrometry (LC-MS) assay for the determination of selected non-stero idal anti-inflammatory drugs (NSAIDs), namely diclofenac sodium (DIC), fluf enamic acid (FLU), indomethacin (IND) and ketoprofen (KET), tither individu ally or in mixtures, was developed. The examined drugs were injected onto S him-pack GLC-CN column and were eluted with a mobile phase consisting of ac etonitrile and 20 mM ammonium acetate solution (5:1 v/v)/pH 7.4 at a flow r ate 1 ml min(-1). The mass spectrometer. operated in the single ion monitor ing mode, was programmed to admit the negative ions [M-H](-) at m/z 295.9 ( DIC), 280.1 (FLU), 355.8 (IND) and 252.9 (KET), respectively. The calibrati on curves were linear (r greater than or equal to 0.9993) over the concentr ation range 50-300 ng ml(-1) (FLU, DIG) and 100-500 ng ml(-1) (KET, IND) wi th detection limits of 0.5-3.0 ng. The mean predicted concentrations for th e analytes were in the range - 5.9 and 5.2% of the nominal concentrations. Within-day and between-day precision were in the range of 0.8-9.1% of the R .S.D. Mean recovery percentages of the individual compounds from laboratory -made mixtures and pharmaceutical formulations were (99.5-101.5%) and (100. 6-102.2%), respectively. (C) 2001 Elsevier Science B.V. All rights reserved .