Single bubble in‐tube microextraction coupled with capillary electrophoresis

Abstract

Headspace (HS) extraction is a sample pretreatment technique for volatile and semivolatile organic compounds in a complex matrix. Recently, in-tube microextraction (ITME) coupled with CE using an acceptor plug placed in the capillary inlet was developed as a simple but powerful HS extraction method. Here, we present single bubble (SB) ITME using a bubble hanging to the capillary inlet immersed in a sample donor solution as a HS of submicroliter volume (∼200 nL). The analytes evaporated to the bubble were extracted into the acceptor phase through the capillary opening, then electrophoresis of the enriched extract was carried out. Since the bubble volume was much smaller than a conventional HS volume (∼1 mL), it was filled with the evaporated analytes rapidly and the analytes could be enriched much faster compared to conventional HS-ITME. Owing to the high surface-to-volume ratio of the SB, 5 min SB-ITME yielded the enrichment factor values similar to those of 10 min HS-ITME. When 5 min SB-ITME at room temperature was applied to a tap water sample, the enrichment factors of 2,4,6-trichlorophenol (TCP), 2,3,6-TCP, and 2,6-dichlorophenol were 53, 41, and 60, respectively, and the LOQs obtained by monitoring the absorbance at 214 nm were 5.6-8.3 ppb, much lower than 200 ppb, the World Health Organization guideline for the maximum permissible concentration of 2,4,6-TCP in drinking water.

Capillary Electrophoresis: A Three-Year Literature Review

“…The detailed protocol for the online coupling of direct immersed-single-drop microextraction (DI-SDME) with a CE-ultraviolet (UV) detector without modifying the commercial CE instrument was described by Jeong et al The protocol allowed for the simultaneous detection of naproxen, ketoprofen, and acidic endogenous components in urine at concentrations less than 10 μg/L. The same research group then explored a novel headspace SDME (HS-SDME) method known as single bubble in-tube microextraction (SB-ITME), demonstrating enhanced enrichment for chlorophenol compounds in tap water samples …”

“…The same research group then explored a novel headspace SDME (HS-SDME) method known as single bubble in-tube microextraction (SB-ITME), demonstrating enhanced enrichment for chlorophenol compounds in tap water samples. 20 Mikova et al reported the online combination of a liquidphase microextraction (LPME) technique, specifically hollowfiber liquid-phase microextraction (HF-LPME), with a commercial CE system through a simple setup. 21 They assembled the disposable HF-LPME device by attaching a porous polypropylene HF extraction unit to a 3D-printed HF holder.…”

Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications—Updated and completely revised edition

“…Additional details, including fundamentals and extensive classifications, can be found in recent reviews [474][475][476]. Among other clever approaches, it is worth mentioning the possibility to use the capillary to add solvents and mix the sample to determine tyrosine kinase inhibitors in plasma [384], additional uses of droplet extraction [477], including single bubble in-tube microextraction [478], and the use of alternative solvents [479] such as deep eutectic solvents [480] or ionic liquids [481]. Pavel Kuban's group recently reported the advantages of at-line coupling of hollow fiber liquid-phase microextraction to CE for trace determination of basic [482,483] and acidic drugs [484] in complex samples.…”