Feasibility of electroextraction as versatile sample preconcentration for fast and sensitive analysis of urine metabolites, demonstrated on acylcarnitines

In this work, we demonstrate the applicability of electroextraction (EE) to urine metabolites. To investigate which urine metabolite classes are susceptible to EE, off-line EE experiments were carried out with a prototype device, in which urine metabolites were electroextracted from ethyl acetate into water. The obtained extracts were examined with direct infusion MS and the results demonstrated that several compound classes could be extracted, amongst which amino acids and acylcarnitines. Acylcarnitines were selected for evaluation of the performance of EE. For this, the EE setup was adapted to capillary EE (cEE) to be able to analyze large urine sample series, and it was coupled online to LC-MS. cEE-LC-MS of acylcarnitines was optimized and characterized. The recovery, linearity, repeatability, and detection limit of the cEE-LC-MS method was good to excellent. To demonstrate the versatility of EE for sample preparation in analytical procedures, extracts were injected into a CZE-MS system, resulting in detection of the acylcarnitines along with more than 100 presumed metabolite peaks. The results presented here indicate that EE can be used as a fast sample preconcentration technique of low abundant urine metabolites, in combination with both LC and CZE.