Impedance model for voltage optimization of parabens extraction in an electromembrane millifluidic device

Comparison of the applicability of electromembrane extraction and liquid-phase microextraction for extraction of non-polar basic drugs from different biological samples: Using clozapine as the model analyte

Understanding and comparing the applicability of electromembrane extraction (EME) and liquid-phase microextraction (LPME) is crucial for selecting an appropriate microextraction approach. In this work, EME and LPME based on supported liquid membranes were compared using biological samples, including whole blood, urine, saliva, and liver tissue. After optimization, efficient EME and LPME of clozapine from four biological samples were achieved. EME provided higher recovery and faster mass transfer for blood and liver tissue than LPME. These advantages were attributed to the electric field disrupting clozapine binding to interfering substances. For urine and saliva, EME demonstrated similar recoveries while achieving faster mass transfer rates. Finally, efficient EME and LPME were validated and evaluated combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The coefficient of determination of all methods was greater than 0.999, and all methods showed acceptable reproducibility (≤14%), accuracy (90%-110%), and matrix effect (85%-112%). For liver and blood with high viscosity and complex matrices, EME-LC-MS/MS provided better sensitivity than LPME-LC-MS/MS. The above results indicated that both EME and LPME could be used to isolate non-polar basic drugs from different biological samples, although EME demonstrated higher recovery rates for liver tissue and blood.

Green strategies using solvent-free biodegradable membranes in microfluidic devices. Liquid phase microextraction and electromembrane extraction

In this work, a novel solvent-free microfluidic method based liquid phase microextraction has been proposed for the first time. A comprehensive study of liquid phase microextraction (LPME) and electromembrane extraction (EME) implemented in microfluidic formats has been carried out to investigate the efficiency of biodegradable membranes (such as agarose) without organic solvent to develop fully environmental microfluidic methods. For this study, non-polar and polar basic compounds (five) were selected as model analytes and different agarose membrane compositions were synthesized and tested with and without organic solvent (solvent-free). Under optimal experimental conditions, the extraction efficiencies obtained using solvent-free LPME-chip devices were similar to the ones obtained using solvent-free EME-chip devices at very low voltages (0.25 V), however, LPME microfluidic format was selected due to its simplicity. The proposed green microfluidic device was successfully applied in urine samples with recoveries between 80 and 93% for all analytes and relative standard deviation below 7% for all analytes. Results were compared with experiments previously conducted using conventional (polypropylene) membranes, observing that solvent-free microfluidic systems based on biodegradable solid support materials have proven to be an attractive alternative and offered the same advantages in terms of membrane stability allowing consecutive extractions compared to supported liquid membranes (SLM) microfluidic methods.

An improved microfluidic device to enhance the enrichment factors in liquid phase microextraction: application to the simultaneous extraction of polar and non-polar acids in biological samples

A new microfluidic device to enhance the enrichment factor in miniaturized systems is proposed. The microfluidic system was design for liquid phase microextractions, and it was applied to the simultaneous extraction of acidic compounds of a wide range of polarity (0.5 < log P < 3). The device operated under stagnant acceptor phase conditions and all the operational parameters involved were optimized. Tributyl phosphate was found to be a new highly efficient supported liquid membrane to simultaneously extract analytes of very different polarities. The optimal donor and acceptor phase were pH 2 and pH 13, respectively. The donor flow rate and the extraction time were investigated simultaneously, offering great versatility with high enrichment factors (EFs). Limits of quantitation were within 0.02 and 0.09 µg mL^-1 for all compounds at 10 µL min^-1 as donor flow rate and 20-min extractions, offering EFs between 11 and 18 with only 200-µL sample volume consumption. The method was successfully applied to human urine samples, observing recoveries between 47 and 90% for all compounds. This new proposed microfluidic system increases the wide range of applications, especially when the analytes are present in lower concentrations in the sample.

Green Method for the Selective Electromembrane Extraction of Parabens and Fluoroquinolones in the Presence of NSAIDs by Using Biopolymeric Chitosan Films

A chitosan biopolymeric membrane was successfully used as a support in a green electromembrane extraction procedure for the simultaneous and selective extraction of seven parabens and three fluoroquinolones in the presence of three non-steroidal anti-inflammatory drugs. The optimal experimental conditions (10 mL donor phase and 50 μL acceptor phase, pH 10 in both phases; 80 V of applied voltage during 15 min of extraction time) were determined, providing high enrichment factors for six of the studied parabens (EF ≥ 90) and the three fluoroquinolones (EF ≥ 50). Wide linear concentration ranges (0.5-500 μg L^-1), good linearity (>97%), low limits of detection (0.2-1.1 μg L^-1), and good repeatability (relative standard deviation values 4-10%) were achieved. The proposed method was successfully applied for the extraction of the target analytes from different kinds of water samples (river, lake, and swimming pool). The usage of a chitosan membrane in the extraction process presents many advantages, as it is a biodegradable and versatile support, offering a good alternative to commercial plastic materials commonly used in this methodology and these procedures.

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.

Electromembrane Extraction of Naphthenic Acids in Produced Water Followed by Ultra-High-Resolution Mass Spectrometry Analysis

Naphthenic acids comprise one of the most toxic compounds of the produced water released from offshore oil platforms. Therefore, developing and applying faster, simpler, and more efficient analytical methods for analyzing naphthenic acids are urgently needed. Electromembrane extraction (EME) uses the electrokinetic migration of target ions through a porous membrane. Herein, the EME method was applied to extract naphthenic acids from produced water. The EME method was optimized, and the optimal conditions encompassed decanol as the organic solvent, the sample with pH 10.0, 5 min of extraction at 200 V, and the ratio 4:1 (borate buffer/matrix, v/v). Electrochemical impedance spectroscopy confirmed charged species' migration from produced water through the EME. Subsequently, all extracts were analyzed by ultra-high-resolution mass spectrometry. The EME efficiency was assessed by comparing the extraction results to the liquid-liquid extraction (LLE) method results. Analytical results showed good linearity for both solvent and matrix curves (R² > 0.98). Low detection limits ranged from 0.10 to 0.13 μg mL^-1 and quantification limits from 0.36 to 0.45 μg mL^-1. Precision and accuracy values ranged from -13.3% to 16.5%. These values fit the proposed method, demonstrating that the EME was more efficient than LLE in naphthenic acid extraction. The EME method preferably extracted aromatic compounds with double-bond equivalence from 6 to 8. The EME coupled with ultra-high-resolution mass spectrometry was demonstrated as a promising analytical approach to naphthenic acid extraction as an efficient and more environmentally friendly alternative to conventional extraction methods.

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.

Electromembrane extraction in microfluidic formats

Electromembrane extraction is a microextraction technique where charged analytes are extracted across a supported liquid membrane and selectively isolated from the sample based on an electrical field. Since the introduction in 2006, there has been continuously increasing interest in electromembrane extraction, and currently close to 50 new articles are published per year. Electromembrane extraction can be performed in different technical configurations, based on standard laboratory glass vials or 96-well plate systems, and applications are typically related to pharmaceutical, environmental, and food and beverages analysis. In addition to this, conceptual research has developed electromembrane extraction into different milli- and microfluidic formats. These are much more early-stage activities, but applications among others related to organ-on-chip systems and smartphone detection indicate unique perspectives. To stimulate more research in this direction, the current article reviews the scientific literature on electromembrane extraction in milli- and microfluidic formats. About 20 original research articles have been published on this subject so far, and these are discussed critically in the following. Based on this and the authors own experiences with the topic, we discuss perspectives, challenges, and future research.

A selective and efficient microfluidic method-based liquid phase microextraction for the determination of sulfonamides in urine samples

Liquid phase microextraction (LPME) into a microfluidic has undergone great advances focused on downscaled and miniaturized devices. In this work, a microfluidic device was developed for the extraction of sulfonamides in order to accelerate the mass transfer and passive diffusion of the analytes from the donor phase to the acceptor phase. The subsequent analysis was carried out by high performance liquid chromatography with UV-DAD (HPLC-DAD). Several parameters affecting the extraction efficiency of the method such as the supported liquid membrane, composition of donor and acceptor phase and flow rate were investigated and optimized. Tributyl phosphate was found to be a good supported liquid membrane which confers not only great affinity for analytes but also long-term stability, allowing more than 20 consecutive extractions without carry over effect. Under optimum conditions, extraction efficiencies were over 96 % for all sulfonamides after 10 minutes extraction and only 10 µL of sample was required. Relative standard deviation was between 3-5 % for all compounds. Method detection limits were 45, 57, 54 and 33 ng mL^-1 for sulfadiazine (SDI), sulfamerazine (SMR), sulfamethazine (SMT) and sulfamethoxazole (SMX), respectively. Quantitation limits were 0.15, 0.19, 0.18 and 0.11 µg mL^-1 for SDI, SMR, SMT SMX, respectively. The proposed microfluidic device was successfully applied for the determination of sulfonamides in urine samples with extraction efficiencies within the range of 86-106 %. The proposed method improves the procedures proposed to date for the determination of sulfonamides in terms of efficiency, reduction of the sample volume and extraction time.

An efficient microfluidic device based on electromembrane extraction for the simultaneous extraction of acidic and basic drugs

The simultaneous extraction of acidic and basic compounds is considered a great challenge. In this work, an efficient and fast microfluidic device is described for the simultaneous determination of acidic and basic drugs by two electromembrane extraction, offering extraction efficiencies over 98% for all analytes in human urine samples and solving the difficulties encountered to date. The sample is submitted into the device and the collected acceptor phase is directly analyzed by diode array detector and high-pressure liquid chromatography (HPLC). The device consisted of three poly(methylmethacrylate) layers and four electrodes to perform EME in two steps in a single device. Two acidic analytes (ketoprofen and naproxen) and two basic analytes (amitriptyline and loperamide) were selected as model analytes. The device proposed works under stable electric field conditions, low current intensities that confers great stability to the supported liquid membrane. After a comprehensive study of the SLM, 1:1 2-nitrophenyl octhyl ether:dodecanol was selected as optimal. This device has also been successfully applied in 1:2 diluted bovine plasma samples with recoveries over 84% and a relative standard deviation below 6%. This microfluidic device needs small sample volumes (lower than 50 μL) and offers short extraction times (10 min) and excellent clean-up. Furthermore, it has proven to be a robust and reproducible device after more than 30 consecutive extractions, and thanks to the low potential required (5 V), it allows its compatibility with a single battery.