Evaluation of a benchtop ion trap gas chromatographic-tandem mass spectrometric instrument for the analysis of a model drug, tebufelone, in plasma using a stable-isotope internal standard.

The performance of a benchtop GC-ion trap MS-MS instrument, the Varian Saturn 4D, was evaluated for the analysis of a model drug, tebufelone, in plasma. The sample preparation scheme was designed to provide a highly complex extract with matrix-derived interferences eluting near and at the retention time of tebufelone and its stable-isotope-labeled analog. The performance of the ion trap in the selected-reaction-monitoring mode was evaluated and also compared with results obtained on a benchtop GC-MS linear quadrupole instrument operated in the selected-ion-monitoring mode. The ion trap, operated in the selected-reaction-monitoring mode, was found to provide a higher degree of selectivity for the analysis of tebufelone. The increased selectivity obtained on the ion trap operated in the selected-reaction-monitoring mode resulted in superior accuracy and precision, as well as a lower limit of quantitation relative to that obtained by the GC-MS analysis. A linear standard curve was obtained over three orders of magnitude and the limit of quantitation for tebufelone in plasma was 100 pg/ml using the GC-ion trap MS-MS instrument.