Online coupling of bead injection lab-on-valve analysis to gas chromatography: application to the determination of trace levels of polychlorinated biphenyls in solid waste leachates

Abstract

Online sorptive preconcentration exploiting renewable solid surfaces, so-called bead injection (BI), in the miniaturized lab-on-valve (LOV) platform is for the first time hyphenated to gas chromatography (GC) for automated determination of trace level concentrations of organic environmental pollutants. Microfluidic handling of solutions and suspensions in LOV is accomplished by programmable flow with a multisyringe flow injection (MSFI) setup. The method involves the incorporation of minute amounts (3 mg) of reversed-phase copolymeric beads with hydroxylated surface (Bond Elut Plexa) into the channels of a poly(ether imide) LOV microconduit, thus serving as a transient microcolumn packed reactor for preconcentration of organic species. The analyte-loaded beads are afterward eluted with 80 microL of ethyl acetate into a rotary injection valve and subsequently introduced via an air stream into the programmable-temperature vaporizer (PTV) injector of the GC. The used beads are then backflushed and delivered to waste. The GC separation and determination is synchronized with the preconcentration steps of the ensuing sample. The potentials of the devised BI-LOV-GC assembly with electron capture detector for downscaling and automation of sample processing were demonstrated in the determination of polychlorinated biphenyls in raw landfill leachates and a leachate containing the Aroclor 1260 congener mixture. By sampling 12 mL of leachates to which 50 vol % methanol was added to minimize sorption onto the components of the flow network, the automated analytical method features relative recovery percentages >81%, limits of quantification within the range of 0.5-6.1 ng L(-1), relative standard deviations better than 9% at the 50 ng L(-1) level, and 25-fold decrease in cost of solid-phase extraction (SPE) consumables as compared with online robotic systems or dedicated setups.