Determination of ropivacaine and its metabolites in human plasma using solid phase microextraction and GG-NPD/GC-MS

The performance of solid-phase microextraction (SPME) in combination with capillary gas chromatography (CGC) to quantify ropivacaine and its metabolites in human plasma was investigated. The analysis was performed using either a nitrogen phosphorus detector (NPD) or a mass-spectrometric detector. For extraction, Carbowax/divinylbenzene, polyacrylate and polydimethylsiloxane fibers were tested. Absorption and desorption times were studied for all analytes separately. The Carbowax/divinylbenzene fiber gave the highest recovery in plasma samples as compared to the other fibers. The effects of temperature, addition of salt, and agitation of the sample were studied. The validation of the method showed that the chromatographic selectivity was satisfactory and all metabolites were well separated. SPME gave higher deviation as compared to published data for solid-phase and liquid-liquid extraction as sample preparation methods but the acceptance criteria for the study validation were well in line with the international criteria. The major disadvantage of SPME in quantitative bioanalysis is that the fiber does not withstand a complete run (standards + blanks + QC samples + patient samples). Also, the duality of fiber and the fiber length can differ from batch to batch. (C) 2001 John Wiley & Sons, Inc.