Rapid and sensitive analysis of diclofenac in human plasma by GC/SIM/MS

An analytical method for the determination of diclofenac with tolfenamic ac id as the internal standard was developed and validated in human plasma by capillary gas chromatography-mass spectrometry (GC/MS). After the addition of the internal standard, the compounds were extracted from plasma at acidi c pH into diethylether, which was then evaporated to dryness. The compounds were derivatized with pentafluoropropionic anhydride (PFPA) and a mixture (1000:2:3, v/w/w) of N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), a mmonium iodide (NPH4I). and dithioerythritol (DTE). They were determined by GC/MS at m/z 349 (a molecular ion) for diclofenac and mit 270 (a base ion) for tolfenamic acid. The recovery of this procedure was 97.8 %, and the li nearity for calibration was 0.9907 as the coefficient factor. The detection and quantitation limits were 0.1 and 0.5 ng/mL, respectively.