Introduction of high nitrogen doped graphene as a new cationic carrier in electromembrane extraction

Solid supports and supported liquid membranes for different liquid phase microextraction and electromembrane extraction configurations. A review

Liquid phase microextraction (LPME) and electromembrane microextraction (EME) can be considered as two of the most popular techniques in sample treatment today. Both techniques can be configurated as membrane-assisted techniques to carry out the extraction. These supports provide the required geometry and stability on the contact surface between two phases (donor and acceptor) and improve the reproducibility of sample treatment techniques. These solid support pore space, once is filled with organic solvents, act as a selective barrier acting as a supported liquid membrane (SLM). The SLM nature is a fundamental parameter, and its selection is critical to carry out successful extractions. There are numerous SLMs that have been successfully employed in a wide variety of application fields. The latter is due to the specificity of the selected organic solvents, which allows the extraction of compounds of a very different nature. In the last decade, solid supports and SLM have evolved towards "green" and environmentally friendly materials and solvents. In this review, solid supports implemented in LPME and EME will be discussed and summarized, as well as their applications. Moreover, the advances and modifications of the solid supports and the SLMs to improve the extraction efficiencies, recoveries and enrichment factors are discussed. Hollow fiber and flat membranes, including microfluidic systems, will be considered depending on the technique, configuration, or device used.

An overview on nanostructure-modified supported liquid membranes for the electromembrane extraction method

Electromembrane extraction (EME) is an extraction method on the micro scale, in which charged compounds are extracted from a donor phase (sample solution) into an acceptor phase via a supported liquid membrane (SLM) containing a water-immiscible organic solvent. To enhance the extraction efficiency and selectivity in this method, some studies have focused on the modification of the SLM, and thus many strategies have been reported for this purpose. One of these techniques is the introduction of nanomaterials in the SLM structure, which can enhance the extraction efficiency. In the current study, the different nanostructures used for SLM modification in the EME method are reviewed. Furthermore, the related analytical parameters of the developed techniques are classified and tabulated. It is hoped that this review will motivate further research in this field using other nanostructures.

Electromembrane extraction of polar substances - Status and perspectives

In this article, the scientific literature on electromembrane extraction (EME) of polar substances (log P < 2) is reviewed. EME is an extraction technique based on electrokinetic migration of analyte ions from an aqueous sample, across an organic supported liquid membrane (SLM), and into an aqueous acceptor solution. Because extraction is based on voltage-assisted partitioning, EME is fundamentally suitable for extraction of polar and ionizable substances that are challenging in many other extraction techniques. The article provides an exhaustive overview of papers on EME of polar substances. From this, different strategies to improve the mass transfer of polar substances are reviewed and critically discussed. These strategies include different SLM chemistries, modification of supporting membranes, sorbent additives, aqueous solution chemistry, and voltage/current related strategies. Finally, the future applicability of EME for polar substances is discussed. We expect EME in the coming years to be developed towards both very selective targeted analysis, as well as untargeted analysis of polar substances in biomedical applications such as metabolomics and peptidomics.

A low-voltage electro-membrane extraction for quantification of imatinib and sunitinib in biological fluids

Aim: Hollow-fiber-based supported liquid membrane was modified utilizing nanostructures such as graphite, graphene oxide or nitrogen-doped graphene oxide, for electro-membrane extraction (EME) of imatinib and sunitinib from biological fluids. By applying these conductive nanostructures, a low-voltage EME device (6.0 V) was fabricated. Materials & methods: A response surface methodology through central composite design was used to evaluate and optimize effects of various essential factors that influence on normalized recovery. Results: Optimal extraction conditions were set as, 1-octanol with 0.01 % (w/v) graphene oxide functioning as the supported liquid membrane, an extraction time of 17.0 min, pH of the acceptor and the donor phase of 2.8 and 7.9, respectively. Conclusion: The method was successfully applied to quantify imatinib and sunitinib in biological fluids.

Comparison of three electromembrane-based extraction systems for NSAIDs analysis in human urine samples

A comparative study on the extraction efficiency of five non-steroidal anti-inflammatories was carried out using three different electromembrane extraction (EME) devices with different geometries. The employed setups were (a) a hollow fiber configuration (HF-EME), (b) a microfluidic device that allows working in semi-dynamic mode (μF-EME), and (c) a static miniaturized flat membrane device (FM-EME). Each system was applied to the extraction of salicylic acid (SAC), ketoprofen (KTP), naproxen (NAX), diclofenac (DIC), and ibuprofen (IBU) and subsequent determination by high-performance liquid chromatography with UV and fluorescence detection (HPLC/UV-DAD-FLD). Voltage, pH composition, and extraction time were optimized for all devices. Additionally, volume ratio was investigated for HF-EME and FM-EME and flow rate for the microfluidic device. HF-EME provides the best result in terms of sensitivity with a limit of detection (LOD) between 0.1 and 1.5 ng mL^-1 for SAC and KTP, respectively, while LODs for μF-EME were between 100 ng mL^-1 and 400 ng mL^-1 for SAC and DIC, respectively; however, a lower amount of sample was required. Finally, the obtained results, in terms of enrichment factors and extraction recoveries, were discussed to establish the advantages and disadvantages of each device. The proposed EME methods were successfully applied to the determination of the target analytes in fortified human urine samples. Graphical abstract.

Carrier-mediated extraction: Applications in extraction and microextraction methods

The present review is mainly focused on the overview of carrier mediated extraction (principles and applications) being reported over the last two decades and discusses the extraction process through carriers in various extraction methods such as Bulk liquid membranes, supported liquid membranes, emulsion liquid membranes and polymer inclusion membranes. Several types of carriers such as neutral, anionic, cationic, macrocyclic and supramulecular carriers are discussed. Also their application for metal, anions, drugs and environmental compounds are investigated. Carriers have been demonstrated to be useful for the selective extraction and recovery of numerous cations and anions enhancing the extraction properties of traditional solvent extraction and ion-exchange processes. Several types of carriers have different transport mechanisms. In these mechanisms, transport configurations are addressed and emphasized and the detailed information on the type of carrier are presented along with their specific separation modes. The performance of different carriers in terms of selectivity as well as efficiency are also discussed. Finally, the application of different carriers for the extraction of various compounds are compared and reviewed. To our best knowledge no reviews have been published on carrier-mediated extraction methods.

Electromembrane extraction-Recent trends and where to go

Electromembrane extraction (EME) is an analytical microextraction technique, where charged analytes (such as drug substances) are extracted from an aqueous sample (such as a biological fluid), through a supported liquid membrane (SLM) comprising a water immiscible organic solvent, and into an aqueous acceptor solution. The driving force for the extraction is an electrical potential (dc) applied across the SLM. In this paper, EME is reviewed. First, the principle for EME is explained with focus on extraction of cationic and anionic analytes, and typical performance data are presented. Second, papers published in 2016 are reviewed and discussed with focus on (a) new SLMs, (b) new support materials for the SLM, (c) new sample additives improving extraction, (d) new technical configurations, (e) improved theoretical understanding, and (f) pharmaceutical new applications. Finally, important future research objectives and directions are defined for further development of EME, with the aim of establishing EME in the toolbox of future analytical laboratories.

Rotating electrode in electro membrane extraction: a new and efficient methodology to increase analyte mass transfer

Rotating electrode electromembrane extraction (REEME) as a new EME approach was introduced for the extraction of basic drugs from different matrices.