CAPILLARY GAS-CHROMATOGRAPHIC METHOD FOR THE MEASUREMENT OF SMALL CONCENTRATIONS OF MONOETHYLGLYCINEXYLIDIDE AND LIDOCAINE IN PLASMA

The major metabolite of lidocaine, monoethylglycinexylidide (MEGX) is currently used as a dynamic marker of liver function. It has been prov en, in recent advances, that the determination of MEGX formation after intravenous injection of lidocaine was an effective means of assessin g liver dysfunction in critically ill patients. An accurate and sensit ive gas chromatographic method has been developed for the determinatio n of small quantities of MEGX formed in such cases. The procedure invo lves a solid-phase extraction and injection of the extract (splitless mode) into a gas chromatograph equipped with a capillary column and ni trogen-phosphorus detector. The limit of detection is 1 ng/ml and the Limit of quantification is 2.5 ng/ml. The response is linear up to 50 ng/ml. The inter- and intra-assay coefficients of variation for MEGX a nd lidocaine are between 5 and 9%. This method can be used for the det ermination of small concentrations of MEGX in plasma and could be appl ied to analysis of small amounts of many other nitrogenous molecules. (C) 1998 Published by Elsevier Science B.V. All rights reserved.