Determination of Local Anesthetics in Human Plasma by Liquid-Liquid-Liquid Microextraction Coupled with High Performance Liquid Chromatography

Abstract

Liquid-liquid-liquid microextraction (LLLME) coupled with high-performance liquid chromatography was developed for the simultaneous determination of three local anesthetics, lidocaine, bupivacaine, and tetracaine in human plasma. The effects of the stirring rate, the extraction time, and the pH in the donor phase on the enrichment factor of analytes were investigated. Optimal experimental conditions, 200 μL benzene as the organic phase, 1.0 μL 0.2 mol/L HCl as the acceptor phase, 250 rpm of the stirring rate, and 45 min of the extraction time, were obtained. Under these conditions, high enrichment factors (more than 305-fold for all analytes) were achieved. The linear ranges of analytes studied were from 0.025 to 5 mg/L except tetracaine, for which the range was from 0.05 to 5 mg/L with correlation coefficients higher than 0.996. The limits of detection were 0.005 mg/L for lidocaine, 0.015 mg/L for bupivacaine, and 0.025 mg/L for tetracaine at signal-to-noise ratio of 3 ( S/ N=3). The relative standard deviations were lower than 5%. With LLLME, some substances in the human plasma, which interfered in the determination of analytes, were eliminated efficiently. The method with little solvent consumption was sensitive and suitable for determination of lidocaine, bupivacaine, and tetracaine in human plasma. This method was applied to the specimen of the patient who was treated with local anesthesia of lidocaine and bupivacaine revealed that simultaneous determination of above two local anesthetics in human plasma was possible.