Development and Evaluation of a 66-Well Plate Using a Porous Sorbent in a Four-Phase Extraction Assisted by Electric Field Approach

Enhancing Analytical Sensitivity and Selectivity for Methylene Blue Determination in Water Samples by Using Multiphase Electroextraction Coupled with Optical Absorption Spectroscopy and Surface-Enhanced Raman Scattering

While optical analysis spectroscopy offers operational ease and low cost, it suffers from limitations regarding sensitivity when it comes to analyzing analytes at low concentrations. On the other hand, surface-enhanced Raman spectroscopy (SERS) offers high sensitivity but low selectivity in complex matrices. In this study, we have effectively addressed these challenges by integrating multiphase electroextraction (MPEE) as a sample preparation technique with these two spectroscopic methods for determining methylene blue (MB) dye in tap water samples. A Box-Behnken design was utilized for optimizing electroextraction parameters such as extraction time, pH, and acetonitrile percentage in the donor phase. After optimization, optical absorption spectroscopy results in a linear analytical curve within the range of 30 to 375 mg L-1 of MB, with method validation demonstrating high precision (relative standard deviation between 3.0 and 9.9%), recovery (99-105%), and detection and quantification limits of 1.3 and 4.0 μg L-1, respectively. On the other hand, using SERS, it was possible to detect MB in concentrations as low as 0.05 μg L-1. The extremely low concentrations of MB detected (in the range of a few ppb and ppt) and the acceptable validation performance parameters obtained highlight the potential of MPEE to enhance the applicability of spectroscopic techniques in routine analyses, especially when dealing with complex and challenging samples.

Electromigration of Charged Analytes Through Immiscible Fluids in Multiphasic Electrophoresis

Multiphasic buffer systems have been of greatest interest in electrophoresis and liquid-liquid electrotransfer; this study extends that foundation by exploring the interplay of the geometric and viscous properties of an interleaving oil layer on the electrotransfer of a charged analyte from an aqueous solution into a hydrogel. We utilized finite element analysis to examine two complementary configurations: one being electrotransfer of a charged analyte (protein) in an aqueous phase into a surrounding hydrogel layer and another being electrotransfer of the protein from that originating aqueous phase - through an interleaving oil layer of predetermined viscosity and thickness - and into a surrounding hydrogel layer. Results indicate that the presence of an oil layer leads to increased skew of the injected peak. To explain this difference in injection dispersion, we utilize Probstein's framework and compare the Péclet (Pe) number with the ratio between length scales characteristic to the axial and radial dispersion, respectively. The formulation assigns electrotransfer conditions into six different dispersion regimes. We show that the presence or absence of an interleaving oil layer moves the observed peak dispersion into distinct electrotransfer regimes; the presence of an oil layer augments the electrophoretic mobility mismatch between the different phases, resulting in a five-fold increase in Pe and a six-fold increase in the ratio between the axial to radial dispersion characteristic lengths. We further show that oil viscosity significantly influences resultant injection dispersion. A decrease in oil-layer viscosity from 0.08 Pa·s to 0.02 Pa·s results in a >100% decrease in injection dispersion. Our theoretical predictions were experimentally validated by comparing the electrotransfer regimes of three different mineral oil samples. We show that lowering the oil viscosity to 0.0039 Pa·s results in an injection regime similar to that of the absence of an oil layer. Additionally, we measure the migration distance and show that average electromigration velocity over the transit duration is inversely proportional to the viscosity of an interleaving oil layer. Understanding of the impact of electrotransfer of charged species across multiple immiscible fluid layers on peak dispersion informs the design of multiphasic electrophoresis systems.

Electroextraction of methylene blue from aqueous environmental samples using paper points coupled with hollow fiber membranes

This article introduces a novel approach by coupling paper points with hollow fiber membrane for electroextraction (PP-HF-EE). The method was innovatively applied to extract methylene blue (MB) from large water volumes (up to 580 mL). A comprehensive study of six key parameters - organic filter, acceptor and donor phase composition, extraction time, applied voltage, and sample volume - was conducted using conventional flatbed scanning and digital image analysis. Our results revealed that extraction performance was primarily influenced by time, with low voltages (50 V) and low-conductivity organic filters (1-decanol) yielding comparable results to higher settings (300 V or 1-pentanol). Under optimized conditions (50 V, 60 min, 1-decanol as the organic filter), analytical performance parameters were assessed, demonstrating acceptable precision (RSD <18% for intra- and inter-day measurements) within a linear range of 5-100 μg L-1 (r = 0.98). PP-HF-EE demonstrated reliability through stable and reproducible electric current measurements during all extraction studies. Utilizing an extremely cost-effective detection system, PP-HF-EE achieved detection limits in the low ppb range, highlighting its potential as a promising variation of electromembrane extraction for environmental sample analysis.

Multiphase electroextraction of malachite green from surface water and its determination using digital imaging and chemometric tools

This study introduces a novel method for the quantification of malachite green (MG), a pervasive cationic dye, in surface water by synergizing multiphase electroextraction (MPEE) with digital image analysis (DIA) and partial least square discriminant analysis. Aimed at addressing the limitations of conventional DIA methods in terms of quantitation limits and selectivity, this study achieves a significant breakthrough in the preconcentration of MG using magnesium silicate as a novel sorbent. Demonstrating exceptional processing efficiency, the method allows for the analysis of 10 samples within 20 min, exhibiting remarkable sensitivity and specificity (over 0.95 and 0.90, respectively) across 156 samples in both training and test sets. Notably, the method detects MG at low concentrations (0.2 µg L-1) in complex matrices, highlighting its potential for broader application in environmental monitoring. This approach not only underscores the method's cost-effectiveness and simplicity but also its precision, making it a valuable tool for the preliminary testing of MG in surface waters. This study underscores the synergy among MPEE, DIA, and chemometric tools, presenting a cost-efficient and reliable alternative for the sensitive detection of water contaminants.

Multiphase electroextraction as a simple and fast sample preparation alternative for the digital image determination of doxorubicin in saliva

Monitoring chemotherapeutic drugs in biological fluids is, in many cases, extremely important for dose adjustment, the maintenance of therapies, and the control of side effects. In this work, a method for determining the doxorubicin in saliva by digital image analysis (DIA) was optimised and validated. Images from a paper point were obtained using a conventional and cheap flatbed scanner at a 600 ppp resolution. The RGB data channels were obtained from the images in a region of 15 × 15 pixels around the sorbent vertex. The paper point was used as sorbent material in sample preparation using a multiphase electroextraction system. Following optimisation using a Doehlert experimental design, the method was able to simultaneously extract 66 samples in 20 min. The high selectivity of the electric field associated with the sorption capacity of the cellulosic material allowed the chemotherapy drug to be pre-concentrated and quantified in a range between 50 and 500 μg L^-1 (R² > 0.98). The method also exhibited adequate parameters (limits of detection and quantification, recovery, and precision) indicating its potential application in the monitoring of doxorubicin and similar drugs in saliva.

Electric field-assisted multiphase extraction to increase selectivity and sensitivity in liquid chromatography-mass spectrometry and paper spray mass spectrometry

In this work, for the first time, chromatographic paper was used for a multiphase extraction assisted by an electric field (MPEF) and directly coupled to paper spray mass spectrometry (PS-MS). Using this approach, five tricyclic antidepressants (TCAs) were determined in oral fluid. Firstly, the MPEF conditions were optimized using liquid chromatography-mass spectrometry (LC-MS/MS). The effects of the chromatographic paper and the types of electrolyte used in the acceptor phase, the organic solvent type and the amount used in the donor phase, the extraction time, and the applied electric potential were all investigated. After optimization, the analytes were extracted from the donor solution (sample and acetonitrile 1:1 (v/v)) over a period of 10 min at 300 V, crossing the free liquid membrane (1-octanol) and reaching the acceptor phase (chromatographic paper wetted with 400 mmol L^-1 acetic acid). The method using LC-MS/MS was validated, demonstrating a linear range from 2 to 12 ng mL^-1, with detection and quantification limits of 0.13-0.25 and 0.44-0.84 ng mL^-1, respectively, an intraday precision of less than 20%, and no matrix effect observed. The optimized MPEF conditions were then applied to determine TCAs by PS-MS and for this analysis cyclobenzaprine was used as an internal standard. The easy, fast and direct approach of coupling MPEF with PS-MS analysis, as well as the pre-concentration and the low standard deviation of replicates (less than 20%), demonstrates that this method can be useful for screening in clinical and toxicological analysis.

Nonaqueous Miscible Liquid-Liquid Electroextraction for Fast Exhaustive Enrichment of Ultratrace Analytes by an Exponential Transfer and Deceleration Mechanism

Conventional electrical-field-assisted sample preparation (EFASP) methods rely on analyte transfer between immiscible phases and require at least one aqueous phase in contact with the electrode. In this paper, we report a novel nonaqueous miscible liquid-liquid electroextraction (NMLEE) technique that enables fast exhaustive enrichment of ultratrace analytes from a milliliter-level donor in a vial to a microliter-level acceptor in a tube. Miscible nonaqueous solvents are used for the donor and acceptor to overcome common EFASP problems such as high charge or mass transfer resistance, loss of analytes in the membrane phase, water electrolysis, back-extraction, bubble generation, and difficulties in the application of high voltage for fast migration. According to theoretical derivation and experimental verification results, the concentrations of analytes in the donor and their migration velocity in the acceptor both decrease exponentially with time, and the extraction recovery correlates linearly with the current variation. These mechanisms result in efficient enrichment by forming an analyte-enriched zone and allow the extraction progress and recovery to be monitored and estimated based on the current variation. NMLEE was coupled with liquid chromatography-mass spectrometry to analyze 10 amphetamine-type drugs, atropine, nortriptyline, and methadone in blood and urine samples. This method provided low limits of detection (0.003-0.1 ng·mL^-1), satisfactory extraction recoveries (89.6-104.1%), and RSDs (<12.3% for intraday and <8.8% for interday), which met the requirements of the ICH guidelines. This study may contribute to the further development of EFASP methods for effective ultratrace analyses in forensic science.

Large-volume electric field-assisted multiphase extraction of malachite green from water samples: A multisample device and method validation

In this work, a new large-volume multiphase, multi-sample electroextraction device was developed and applied to selectively extract malachite green (MG) from water samples. This device was easily constructed with ordinary materials and capable of extracting ten samples simultaneously, obtaining MG preconcentrated on a solid support, to fit into a pipette tip. A multi-well plate was applied to extract MG from aquaculture water samples, and the extracts containing the desorbed MG were analysed by LC-DAD and LC-MS/MS. The signals from both detectors were used in two independent validation procedures. Linearity, matrix effect, selectivity, precision, trueness, and limits of detection and quantification were all evaluated. For both detectors, linearity was demonstrated in the range of 0.5-5 μg L^-1 (R² > 0.98). Matrix effect was insignificant for LC-DAD only, and the average preconcentration factor was about 60 times. Recoveries ranged from 94 to 113% for LC-DAD and 95-115% for LC-MS/MS analysis. ANOVA was applied to estimate the standard deviation under repeatability (6.96-8.61% for LC-DAD and 5.98-7.41% for LC-MS/MS) and within-reproducibility (6.96-8.61% for LC-DAD and 6.56-7.41% for LC-MS/MS) conditions. The limits of detection and quantification for LC-MS/MS analysis were 4.29 and 28.74 ng L^-1, respectively, while, for LC-DAD, these limits were 14.29 and 95.81 ng L^-1, respectively. The results demonstrated that the developed method was suitable for determining MG in water samples, and the large-volume multiphase, multi-sample electroextraction device proved to be a powerful sample preparation technique to obtain high clean-up and large preconcentration levels, which are of paramount importance for environmental applications.

Cellulose cone tip as a sorbent material for multiphase electrical field-assisted extraction of cocaine from saliva and determination by LC-MS/MS

A porous and hydrophilic sorbent material was used in an extraction system, assisted by electric fields, for the extraction of cocaine in saliva and subsequent determination by ultra-high-performance liquid chromatography associated with sequential triple quadrupole mass spectrometry (UHPLC-MS/MS). The cellulose-based material was characterized by scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The time and voltage variables applied in the extraction process were investigated through a Doehlert experimental design, and with the best conditions found (35min and 300 V) some validation parameters were evaluated. The established working range was 1-100 μg L^-1 (R² > 0.99), and the detection and quantification limits determined were 0.3 and 0.8 μg L^-1, respectively. Recoveries from 80 to 115% and coefficient of variation ≤15 and 16% for intra-day and inter-day assays, respectively, were obtained for sample concentrations of LOQ, 5, 25, and 75 μg L^-1, indicating satisfactory accuracy and precision for the proposed method. In addition, the method presented no matrix effect, and the extraction efficiency was between 56 and 70%. The results showed that the material used has adequate physicochemical characteristics and can be applied as a sorbent and electrolyte support in multiphase extractions using electric fields.