Ionic liquid-based headspace in-tube liquid-phase microextraction coupled with capillary electrophoresis for sensitive detection of phenols

Progress in on-line, at-line, and in-line coupling of sample treatment with capillary and microchip electrophoresis over the past 10 years: A review

The review presents an evaluation of the development of on-line, at-line and in-line sample treatment coupled with capillary and microchip electrophoresis over the last 10 years. In the first part, it describes different types of flow-gating interfaces (FGI) such as cross-FGI, coaxial-FGI, sheet-flow-FGI, and air-assisted-FGI and their fabrication using molding into polydimethylsiloxane and commercially available fittings. The second part deals with the coupling of capillary and microchip electrophoresis with microdialysis, solid-phase, liquid-phase, and membrane based extraction techniques. It mainly focuses on modern techniques such as extraction across supported liquid membrane, electroextraction, single drop microextraction, head space microextraction, and microdialysis with high spatial and temporal resolution. Finally, the design of sequential electrophoretic analysers and fabrication of SPE microcartridges with monolithic and molecularly imprinted polymeric sorbents are discussed. Applications include the monitoring of metabolites, neurotransmitters, peptides and proteins in body fluids and tissues to study processes in living organisms, as well as the monitoring of nutrients, minerals and waste compounds in food, natural and wastewater.

Single bubble in-tube microextraction coupled with capillary electrophoresis

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.

Voltammetric Sensor Based on Molecularly Imprinted Chitosan-Carbon Nanotubes Decorated with Gold Nanoparticles Nanocomposite Deposited on Boron-Doped Diamond Electrodes for Catechol Detection

Phenolic compounds such as catechol are present in a wide variety of foods and beverages; they are of great importance due to their antioxidant properties. This research presents the development of a sensitive and biocompatible molecular imprinted sensor for the electrochemical detection of catechol, based on natural biopolymer-electroactive nanocomposites. Gold nanoparticle (AuNP)-decorated multiwalled carbon nanotubes (MWCNT) have been encapsulated in a polymeric chitosan (CS) matrix. This chitosan nanocomposite has been used to develop a molecular imprinted polymers (MIP) in the presence of catechol on a boron-doped diamond (BDD) electrode. The structure of the decorated MWCNT has been studied by TEM, whereas the characterization of the sensor surface has been imaged by AFM, demonstrating the satisfactory adsorption of the film and the adequate coverage of the decorated carbon nanotubes on the electrode surface. The electrochemical response of the sensor has been analyzed by cyclic voltammetry (CV) where excellent reproducibility and repeatability to catechol detection in the range of 0 to 1 mM has been found, with a detection limit of 3.7 × 10-5 M. Finally, the developed sensor was used to detect catechol in a real wine sample.