Evaluation of solid-phase microextraction in combination with gas chromatography (SPME-GC) as a tool for quantitative bioanalysis

Abstract

Solid-phase microextraction in combination with capillary gas chromatography and a nitrogen–phosphorus detector as a bioanalysis tool was investigated. Lidocaine and three of its metabolites were used as model compounds, and human plasma and urine samples were used in this evaluation. Carbowax–divinylbenzene, polyacrylate, and polydimethylsiloxane fibers were tested. Absorption times were studied for all analytes separately. Carbowax–divinylbenzene fiber gave highest recovery in plasma samples compared to other fibers. Effects of temperature, addition of salt and agitation of the sample were studied. Recovery from plasma was improved by 2–4 times at pH 9 compared to pH 3. This is due to analytes not charged at high pH. Recovery from water was 2–4 times higher than from plasma using Carbowax–divinylbenzene coated fiber. This is due to protein binding of analytes in plasma. Chromatographic selectivity was high and all metabolites were well separated. Calibration curves were linear for all metabolites in human plasma and urine in the range 0.035–7.7 μM for lidocaine and 2,6-xylidine while 0.1–3.5 μM for glycinexylidide (GX) and monoethylglycinexylidide (MEGX). Precision, measures as relative standard deviation, was less than 15% and accuracy was in the range 80–115%. Limits of quantitation using plasma were 0.035 μM (8 ng/mL), 0.035 μM (4 ng/mL), 0.100 μM (18 ng/mL), and 0.100 μM (21 ng/mL) for lidocaine, 2,6-xylidine, GX, and MEGX, respectively. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 308–315, 2000