A simple sample pretreatment device with supported liquid membrane for direct injection of untreated body fluids and in‐line coupling to a commercial CE instrument

Abstract

A simple sample pretreatment device was developed employing extractions across supported liquid membranes (SLMs) and in-line coupling to a commercial CE instrument. The device consisted of two polypropylene conical units interspaced with a polypropylene planar SLM, which were impregnated with 1-ethyl-2-nitrobenzene. The two units and the SLM were pressed against each other, donor unit was filled with 40 μL of an untreated body fluid and acceptor unit with 40 μL of DI water. The device was then placed into conventional CE vial fitted with a soft spring, which was depressed during injection into CE capillary and ensured that the SLM was not ruptured. Position of separation capillary injection end and high-voltage electrode in the CE instrument was optimized in order to ensure efficient injection of pretreated body fluids. The device can be easily assembled/disassembled and SLMs can be replaced after each extraction thus minimizing sample carry-over, avoiding tedious SLM regeneration, and reducing total pretreatment time and costs. The pretreatment device was examined by direct injection of human urine and serum spiked with nortriptyline, haloperidol, and loperamide. The basic drugs were diffusionaly transported across the SLM within 10 min and were injected into the separation capillary directly from the SLM surface in the acceptor unit, whereas matrix components were retained by the SLM. The in-line SLM-CE method showed good repeatability of peak areas (3.8-11.0%) and migration times (below 1.4%), linear relationship (r(2) = 0.990-0.999), and low LODs (12-100 μg/L).