In liquid phase microextraction, high enrichment factors (EFs) can be obtained using an acceptor phase of small volume. By hanging an acceptor drop at the separation capillary tip, single drop microextraction (SDME) can be in-line coupled with capillary electrophoresis (CE). The small surface-to-volume ratio of the drop enables high EFs to be obtained in a short time. One practical issue in SDME is how to keep the drop attached to the capillary stably. Here, we present novel but extremely simple in-tube microextraction (ITME) using the liquid inside the capillary as an acceptor phase, without forming a drop at the capillary tip. In this report, we demonstrate headspace (HS) extraction-ITME-CE fully automated using a commercial CE instrument. As a first example of HS-ITME-CE, chlorophenols in an aqueous sample solution were extracted into the acceptor plug in a separation capillary, simply by placing the capillary filled with a basic run buffer in the HS above the sample, and then electrophoresis of the extracts in the capillary was carried out. Owing to the robust nature of the acceptor phase, the extraction temperature and time ranges of HS-ITME can be extended significantly, compared to HS-SDME. HS-ITME-CE was first demonstrated for the determination of chlorophenols in a red wine sample using a basic aqueous acceptor plug. It was also applied to extract neutral organic pollutants such as BTEX (benzene, toluene, ethyl benzene, and xylene) from an aqueous sample using an acceptor plug of chloroform. The extracts were then analyzed with a micellar electrokinetic chromatography mode of CE.<br/>We also present single bubble microextraction (SBME) technique coupled with CE, a simple but easy way of conducting HS extraction of a small volume sample for subsequent CE analysis. Instead of using a sealed vessel to prepare a HS, an air bubble much smaller than 1 <i>µ</i>L was formed at the tip of a capillary by injecting a plug of air into the capillary containing an acceptor plug and ejecting the air plug after immersing the capillary into a sample donor. Then, SBME-CE was performed using the acceptor plug remained in the capillary. Due to the small volumes of the bubble headspace and acceptor plug, it was possible even for a small volume donor to retain a high ratio of the donor and acceptor volumes for high enrichment factors. All the headspace extraction steps were carried out automatically using a commercial CE instrument without modification.

Simple but powerful headspace extraction methods using a commercial capillary electrophoresis instrument

251st National Meeting (2016)

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