COMPARISON OF P-FLUOROKETOROLAC AND [O-18(3)]KETOROLAC FOR USE AS INTERNAL STANDARDS FOR THE DETERMINATION OF KETOROLAC BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY (GC MS)/

A chemical and a stable-isotope analog, p-fluoroketorolac and [O-18(3) ]ketorolac respectively, were directly compared for applicability as i nternal standards for the determination of ketorolac in plasma samples using gas chromatography/mass spectrometry (GC/MS) with selective-ion -monitoring detection, following derivatization to form the methyl est ers. This comparison involved analyzing ketorolac calibration standard s and spiked plasma samples that contained both internal standard cand idates. The response for ketorolac and each internal standard was moni tored simultaneously and electronically integrated peak heights were o btained. Thus, for each analysis performed, a response ratio was obtai ned for each internal standard relative to an identical ketorolac resp onse. Linearity of response for ketorolac calibration standards and ac curacy for spiked plasma sample analysis were compared using each inte rnal standard. The use of [O-18(3)]ketorolac as the internal standard provided superior accuracy data for the analysis of ketorolac in plasm a samples. (C) 1998 Elsevier Science B.V. All rights reserved.