Capillary electrophoresis-mass spectrometry using an in-line sol-gel concentrator for the determination of methionine enkephalin in cerebrospinal fluid

摘要

In this study,a CE-MS method using a monolithic sol-gel concentrator for in-line solid-phase extraction(SPE)is evaluated for the analysis of methionine enkephalin in biological samples.Operational SPE parameters such as sample pH,loading volume,elution volume and composition have been studied.After optimization of the in-line preconcentration methodology,a 40-fold preconcentration was demonstrated for a methionine enkephalin test solution using a loading volume of 3200 nL.The method was linear in the range from 62.5 to 1000 ng/mL(R-2>0.99).R.S.D.values for migration times and peak areas were 1.2% and 8.4%,respectively.Finally, the analysis of cerebrospinal fluid samples spiked with methionine enkephalin and deproteinized with perchloric acid(1:1,v/v)showed a detection limit(S/N=3)of approximately 1 ng/mL(ca.5 nM).The recoveries of methionine enkephalin for three concentration levels(100,10 and I ng/mL)were in the range of 74-91%,demonstrating the promising potential of the methodology for the analysis of biological samples.