Chromatographic behavior of underivatized lidocaine and metabolites in CGC

Determination of some local anesthetics in human serum by gas chromatography with solid-phase extraction

A method of analysis based on solid-phase extraction coupled with capillary gas chromatographic system for determination of mepivacaine, bupivacaine and lidocaine from human serum was developed. As extraction sorbents were used Chromosorb 103, Tenax-GC and Chromosorb T. The best extraction sorbent proved to be Chromosorb 103. Their recoveries ranged from 91 to 94% at the target concentrations of approx. 1.5 microgml(-1) in serum. Relative standard deviation of the recoveries ranged from 3.11 to 5.30 at these concentrations. As internal standard was used lidocaine. The chromatographic analysis was performed on a gas chromatograph equipped with a capillary column, HP-Innowax, and flame ionisation detector. Samples were injected in splitless mode. This method was applied in a stomatological clinic to healthy volunteers to whom superior-posterior alveolar nerve block anesthesia with mepivacaine was administered.

Utility of nonaqueous capillary electrophoresis for the determination of lidocaine and its metabolites in human plasma: a comparison of ultraviolet and mass spectrometric detection

A nonaqueous capillary electrophoresis/electrospray mass spectrometry method for the separation of lidocaine (LID) and two of its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), has been developed. The separation medium was: 70 mM ammonium formate and 2.0 M formic acid in acetonitrile/methanol (60:40 v/v). With a sheath liquid of methanol/water (80:20 v/v) containing 2% formic acid and positive ion detection, reproducible determinations (8-11% relative standard deviation (RSD)) of lidocaine and its metabolites were performed in spiked human plasma. The limits of detection (LODs) were between 69.1 and 337 nM. The influences of sheath liquid composition, nebulizing gas pressure and drying gas temperature on the separation were examined.

Separation of lidocaine and its metabolites by capillary electrophoresis using volatile aqueous and nonaqueous electrolyte systems

The separation of the basic drug lidocaine and six of its metabolites has been investigated both by using volatile aqueous electrolyte system, at low pH and by employing non-aqueous electrolyte systems. In aqueous systems, the best separation of the compounds under the investigated conditions was achieved by using the electrolyte 60 mM trifluoroacetic acid (TFA)/triethylamine (TEA) at pH 2.5 containing 15% methanol. With this electrolyte, all seven compounds were well separated with high efficiency and migration time repeatability. The separations with bare fused-silica capillaries and polyacrylamide-coated capillaries were compared with higher separation efficiency with the latter. On the other hand, near baseline separation of all the seven compounds was also obtained by employing the non-aqueous electrolyte, 40 mM ammonium acetate in methanol and TFA (99:1, v/v), with comparable migration time repeatability but lower separation efficiency relative to the aqueous system.

High-performance liquid chromatography-tandem electrospray mass spectrometry for the determination of lidocaine and its metabolites in human plasma and urine

A sensitive, selective and accurate high-performance liquid chromatographic-tandem mass spectrometric assay was developed and validated for the determination of lidocaine and its metabolites 2,6-dimethylaniline (2,6-xylidine), monoethylglycinexylidide and glycinexylidide in human plasma and urine. A simple sample preparation technique was used for plasma samples. The plasma samples were ultrafiltered after acidification with phosphoric acid and the ultrafiltrate was directly injected into the LC system. For urine samples, solid-phase extraction discs (C(18)) were used as sample preparation. The limit of quantification (LOQ) was improved by at least 10 times compared to the methods described in the literature. The LOQ was in the range 1.6-5 nmol/l for the studied compounds in plasma samples.

Simultaneous determination of lignocaine hydrochloride and phenylephrine hydrochloride by HPTLC

A high performance thin layer chromatographic (HPTLC) method for the simultaneous quantification of lignocaine hydrochloride (LIG) and phenylephrine hydrochloride (PHE) is described. The mobile phase consisted of ethyl acetate-methanol ammonia (4:1:0.4 v/v/v). The densitometric determination of LIG and PHE was carried out at 262 nm and 291 nm, respectively. The calibration curves of LIG and PHE were linear in the range of 8-18 microg and 4-9 microg, respectively. The method was validated with respect to system precision, method precision, recoveries, intra-day and inter-day variation. The system was applied for the simultaneous determination of LIG and PHE from a new drug delivery system. The results indicate that the method is simple, specific, selective and reliable for simultaneous quantitative determination of LIG and PHE as bulk drug and from formulations.