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 c apillary gas chromatography (CGC) to quantify ropivacaine and its metabolit es in human plasma was investigated. The analysis was performed using eithe r a nitrogen phosphorus detector (NPD) or a mass-spectrometric detector. Fo r extraction, Carbowax/divinylbenzene, polyacrylate and polydimethylsiloxan e fibers were tested. Absorption and desorption times were studied for all analytes separately. The Carbowax/divinylbenzene fiber gave the highest rec overy in plasma samples as compared to the other fibers. The effects of tem perature, addition of salt, and agitation of the sample were studied. The v alidation of the method showed that the chromatographic selectivity was sat isfactory and all metabolites were well separated. SPME gave higher deviati on as compared to published data for solid-phase and liquid-liquid extracti on as sample preparation methods but the acceptance criteria for the study validation were well in line with the international criteria. The major dis advantage of SPME in quantitative bioanalysis is that the fiber does not wi thstand a complete run (standards + blanks + QC samples + patient samples). Also, the duality of fiber and the fiber length can differ from batch to b atch. (C) 2001 John Wiley & Sons, Inc.