Electro membrane extraction combined with capillary electrophoresis for the determination of amlodipine enantiomers in biological samples

Electromembrane extraction--a novel extraction technique for pharmaceutical, chemical, clinical and environmental analysis

Electromembrane extraction (EME) is a novel sample preparation technique in pharmaceutical, chemical, clinical and environmental analysis. This technique uses electromigration across artificial liquid membranes for selective extraction of analytes and sample enrichment from complex matrices. This review focuses on the setup, general procedure and parameters affecting the extraction efficiency of EME. An overview of innovations in EME (on-chip EME, low voltage EME, drop-to-drop EME, pulsed EME and EME followed by low-density solvent based ultrasound-assisted emulsification microextraction) is also presented in this article and attention is focused on the use of EME for pharmaceutical, chemical, clinical and environmental analysis.

Microextraction techniques combined with capillary electrophoresis in bioanalysis

Over the past two decades, many environmentally sustainable sample-preparation techniques have been proposed, with the objective of reducing the use of toxic organic solvents or substituting these with environmentally friendly alternatives. Microextraction techniques (MEs), in which only a small amount of organic solvent is used, have several advantages, including reduced sample volume, analysis time, and operating costs. Thus, MEs are well adapted in bioanalysis, in which sample preparation is mandatory because of the complexity of a sample that is available in small quantities (mL or even μL only). Capillary electrophoresis (CE) is a powerful and efficient separation technique in which no organic solvents are required for analysis. Combination of CE with MEs is regarded as a very attractive environmentally sustainable analytical tool, and numerous applications have been reported over the last few decades for bioanalysis of low-molecular-weight compounds or for peptide analysis. In this paper we review the use of MEs combined with CE in bioanalysis. The review is divided into two sections: liquid and solid-based MEs. A brief practical and theoretical description of each ME is given, and the techniques are illustrated by relevant applications.

Pulsed electromembrane extraction: a new concept of electrically enhanced extraction

In the present work, pulsed electromembrane extraction (PEME) is introduced for the first time as an efficient and inexpensive method for the extraction of ionizable compounds from different matrices. The setup proposed for electromembrane extraction (EME) provides a very stable system and satisfactory repeatability (RSDs<4.4) in comparison with existing methods. In this paper, PEME is conducted for the extraction of model analytes from biological fluids. The effective parameters such as extraction time, applied voltage and the duration of pulse and outage period are optimized using the experimental design. Preconcentration factors in the range of 100-140 and recoveries in the range of 95-108 were obtained in different biological matrices. The linear dynamic ranges of 5-200 ng mL(-1) (with correlation coefficient higher than 0.9955) and limits of detection of 1.0 ng mL(-1) were obtained for both of the drugs. The figures of merit of PEME were compared with the results from conventional EME, which proves the advantages of the proposed technique.

Recent approaches in sensitive enantioseparations by CE

The latest strategies and instrumental improvements for enhancing the detection sensitivity in chiral analysis by CE are reviewed in this work. Following the previous reviews by García-Ruiz et al. (Electrophoresis 2006, 27, 195-212) and Sánchez-Hernández et al. (Electrophoresis 2008, 29, 237-251; Electrophoresis 2010, 31, 28-43), this review includes those papers that were published during the period from June 2009 to May 2011. These works describe the use of offline and online sample treatment techniques, online sample preconcentration techniques based on electrophoretic principles, and alternative detection systems to UV-Vis to increase the detection sensitivity. The application of the above-mentioned strategies, either alone or combined, to improve the sensitivity in the enantiomeric analysis of a broad range of samples, such as pharmaceutical, biological, food and environmental samples, enables to decrease the limits of detection up to 10⁻¹² M. The use of microchips to achieve sensitive chiral separations is also discussed.

Electromembrane extraction: a new technique for accelerating bioanalytical sample preparation

The recent societal requirements to explore more environmentaly friendly solutions in the field of sample preparation have gained increasing focus during recent years. A reduction in the consumption of hazardous organic solvent owing to environmental and cost perspectives, small amounts of sample available and time reduction, have been major incentives for scientists to miniaturize existing sample preparation methods. Some of these challenges were addressed by the introduction of electromembrane extraction (EME), a totally new extraction principle where a potential difference is applied across a thin organic membrane immobilized in the pores in the wall of a porous polypropylene membrane. The potential difference is utilized to extract charged analytes of interest from the sample, across the organic membrane, and into an aqueous acceptor solution present inside the lumen of the hollow fiber. This article focuses on the potential of EME in bioanalysis, including discussions of EME performance.