Direct injection of large volumes of plasma in a column-switching system for the analysis of local anaesthetics. II. Determination of bupivacaine in human plasma with an alkyldiol silica precolumn.
A column-switching high-performance liquid chromatographic system was applied for the determination of bupivacaine in plasma. A 500-microliter plasma sample was directly introduced onto a C18-alkyl-diol silica (ADS) precolumn separating analytes from proteins and polar endogenous compounds. The fraction containing bupivacaine and ropivacaine (internal standard) was back-flushed and transferred to a conventional reversed-phase column (Kromasil C18) for final separation. A single ADS precolumn could withstand more than 50 ml of plasma injections without changing analytical performance. Quantitative studies showed a broad range of linearity (0.033-3.31 micrograms/ml) and high recovery (95-99.9%) with coefficients of variation less than 3.1%. The advantages of the ADS material are its high capability of sample clean-up, due to rapid elution of plasma proteins and endogenous compounds to waste, and its ability to elicit a stable baseline. As a result, UV detection could be performed at 210 nm and clean chromatograms with baseline separation for desired peaks were obtained within 15 min. The detection limit of this system was 10 ng/ml defined by a signal-to-noise ratio of 3:1. The concentration of bupivacaine in patients determined by this method agreed well with the values obtained from an alternative method, making the technique applicable for pharmacokinetic studies in humans.
Analytical Pharmaceutical Chemistry, Uppsala University Biomedical Centre, Sweden.
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D000577:Amides / Q000097:blood*; D000779:Anesthetics, Local / Q000097:blood*; D002045:Bupivacaine / Q000097:blood*; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D010949:Plasma; D015203:Reproducibility of Results; D000077212:Ropivacaine; D013056:Spectrophotometry, Ultraviolet
D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D002045:Bupivacaine