A comprehensive study of a new versatile microchip device based liquid phase microextraction for stopped-flow and double-flow conditions

A new geometry for a versatile microfluidic-chip device based liquid phase microextraction was developed in order to enhance the preconcentration in microfluidic chips and also to enable double-flow and stopped-flow working modes. The microchip device was combined with a HPLC procedure for the simultaneous determination of two different families as model analytes, which were parabens and non-steroidal anti-inflammatories (NSAIDs): Ethyl 4-hydroxybenzoate (Et-P), Propyl 4-hydroxybenzoate (Pr-P), Butyl 4-hydroxybenzoate (Bu-P), IsoButyl 4-hydroxybenzoate (iBu-P), salycilic acid (SAC), ketoprofen (KET), naproxen (NAX), diclofenac (DIC) and ibuprofen (IBU) in urine samples. The new miniaturized microchip proposed in this work allows not only the possibility of working in double-flow conditions, but also under stagnant conditions (stopped-flow) (SF-μLPME). The sample (pH 1.5) was delivered to the SF-μLPME at 20 μL min−1 while keeping the acceptor phase (pH 11.75) under stagnant conditions during 20 min. The highest enrichment factors (between 16 and 47) were obtained under stopped-flow conditions at 20 μL min−1 (sample flow rate) after 20 min extraction; whereas the extraction efficiencies were within the range of 27–81% for all compounds. The procedure provided very low detection limits between 0.7 and 8.5 μg L−1 with a sample volume consumption of 400 μL. Parabens and NSAIDs have successfully been extracted from urine samples with excellent clean up and recoveries over 90% for all compounds. In parallel, the new device was also tested under double flow conditions, obtaining good but lower enrichment factors (between 9 and 20) and higher extraction efficiencies (between 45 and 95) after 7 min extraction, consuming a volume sample of 140 μL. The versatile device offered very high extraction efficiencies and good enrichment factor for double flow and stopped-flow conditions, respectively. In addition, this new miniaturized SF-μLPME device significantly reduced costs compared to the existing analytical techniques for sample preparation since this microchip require few microliters of sample and reagents and it is reusabl

A novel integrated platform enabling simultaneous microextraction and chemical analysis on-chip

Altres ajuts: acords transformatius de la UABThe nature and size of biological, pharmaceutical or environmental analytes complicates their extraction and detection outside of laboratories and near the site of interest by the current chromatographic methods because they require the combination of bulky extraction and detection methods. In order to solve this inefficient centralized control, a ground-breaking and miniaturized proof of concept platform is developed in this work. The platform integrates for the very first time an electro-membrane extraction process and an accurate analyte quantification method in the same device, by using electrochemical impedance spectroscopy (EIS) as analytical technique. The microfluidic flow cell, including the microfluidic components, is fabricated in polymeric materials by rapid prototyping techniques. It comprises a four-electrode platinum thin-film chip that enables the control of the microextraction and the full characterization of the process, i.e., extraction efficiency determination, at the same time. The microfluidic system has been simulated by using computational tools, enabling an accurate prediction of the effect of the different experimental conditions in the microextraction efficiency. The platform has been validated in the microextraction of the nonsteroidal anti-inflammatory drug ketoprofen in a range from 0.5 ppm to 6 ppm. The predicted microextraction efficiency values obtained by EIS were compared with those calculated from the high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD), showing an excellent agreement. This validates the high potential of this integrated and miniaturized platform for the simultaneous extraction by electro-membrane and also the analysis within the platform, solving one of the of most important limitations of current systems

Design and optimisation of new microfluidic devices for biological sample extraction systems

El tractament de mostres és una etapa fonamental en el procés analític especialment en la determinació de compostos de baixa concentració en matrius complexes, a causa de la presència de substàncies majoritàries que emmascaren el senyal de l'analit d'interès en aquestes mostres, dificultant-ne l'anàlisi. A causa de l'interès que genera superar aquest desafiament, cada cop son més el nombre de línies i grups de recerca que se centren a desenvolupar tècniques i sistemes d'extracció de mostres biològiques o mediambientals. L'extracció en fase líquida (LPME) i l'extracció per electromembrana (EME) son tècniques de microextracció basades en l'extracció líquid-líquid. Ambdues tècniques es basen en el transport de l'analit a una fase acceptora aquosa, a través d'una membrana líquida suportada (SLM), que és un dissolvent orgànic immobilitzat als porus de la membrana polimèrica. Aquestes tècniques han estat miniaturitzades i adaptades a dispositius microfluídics fent possible una reducció dels costos de producció, de consum de dissolvent orgànic, de volum de mostra, de temps d'extracció i anàlisi, en comparació a les tècniques tradicionals; a més de facilitar-ne la manipulació i l'acoblament a equips d'anàlisi, com és l'HPLC. La tècnica d'impedància (EIS) és una tècnica electroquímica no destructiva que permet realitzar una caracterització exhaustiva dels sistemes electroquímics, aportant una àmplia informació del que passa a les interfases d'aquests sistemes. Gràcies a aquesta caracterització és possible assolir un profund coneixement dels processos que ocorren en els sistemes de microextracció per EME, permetent millorar aquests sistemes i predint les condicions òptimes d'extracció, reduint considerablement els temps i costos d'optimització. En aquest treball s'han desenvolupat plataformes microfluídiques d'extracció basades tant en les tècniques de LPME com en la d'EME, per aplicar-les posteriorment en mostres biològiques, aconseguint resultats sorprenents tant en els rendiments d'extracció obtinguts, com en la reducció gairebé o per complet de l'efecte matriu. A més, el desenvolupament de noves membranes líquides suportades d'origen natural apropa encara més aquests sistemes microfluídics d'extracció cap a sistemes completament sostenibles, tan necessaris actualment. Finalment, la incorporació d'EIS als dispositius adaptats a EME permet millorar els sistemes actuals, donant l'oportunitat de desenvolupar plataformes més sotisficades que facin possible susperar nous desafiaments.El tratamiento de muestras es una etapa fundamental en el proceso analítico especialmente en la determinación de compuestos de baja concentración en matrices complejas, debido a la presencia de sustancias mayoritarias que enmascaran la señal del analito de interés, dificultando su análisis. Debido al interés que genera superar este desafío, cada vez son más el número de líneas y grupos de investigación que se centran en desarrollar técnicas y sistemas de extracción de muestras biológicas o medioambientales. La extracción en fase líquida (LPME) y la extracción por electromembrana (EME) son técnicas de microextracción basadas en la extracción líquido-líquido. Ambas técnicas, se basan en el transporte del analito a una fase aceptora acuosa, a través de una membrana líquida soportada (SLM), que es un disolvente orgánico inmovilizado en los poros de la membrana polimérica. Estas técnicas han sido miniaturizadas y adaptadas a dispositivos microfluídicos haciendo posible una reducción de los costes de producción, de consumo de disolvente orgánico, de volumen de muestra, de tiempo de extracción y análisis, en comparación a las técnicas tradicionales; además de facilitar su manipulación y acoplamiento a equipos de análisis, como es el HPLC. La técnica de impedancia (EIS) es una técnica electroquímica no destructiva que permite realizar una exhaustiva caracterización de los sistemas electroquímicos, aportando una amplia información de lo que ocurre en las interfases de estos sistemas. Gracias a esta caracterización es posible alcanzar un profundo conocimiento de los procesos que ocurren en los sistemas de microextracción por EME, permitiendo mejorar estos sistemas y prediciendo las condiciones óptimas de extracción, reduciendo considerablemente los tiempos y costes de optimización. En este trabajo se han desarrollan plataformas microfluídicas de extracción basadas tanto en las técnicas de LPME como en la de EME, para su posterior aplicación en muestras biológicas, consiguiendo resultados sorprendentes tanto en los rendimientos de extracción obtenidos, como en la reducción casi o por completo del efecto matriz. Además, el desarrollo de nuevas membranas líquidas soportadas de origen natural acerca aún más a estos sistemas microfluídicos de extracción hacia sistemas completamente sostenibles, tan necesarios actualmente. Finalmente, la incorporación de EIS a los dispositivos adaptados a EME permiten mejorar los sistemas actuales, dando la oportunidad de desarrollar plataformas más sofisticadas que hagan posible superar nuevos desafíos.Sample treatment is critical step in the analytical process, especially in the determination of low concentration compounds in complex matrices, due to the presence of majority substances that cloud the signal of the analyte of interest in these samples, which makes their analysis difficult. Due to the interest in overcoming this challenge, an increasing number of research lines and groups are focusing on developing extraction techniques and systems for biological or environmental samples. Liquid phase extraction (LPME) and electromembrane extraction (EME) are microextraction techniques based on liquid-liquid extraction. Both techniques are based on the transport of the analyte to an aqueous acceptor phase through a supported liquid membrane (SLM), which is an organic solvent immobilised in the pores of the polymeric membrane. These techniques have been miniaturised and adapted to microfluidic devices, enabling a reduction in production costs, organic solvent consumption, sample volume, extraction and analysis time, compared to traditional techniques. Moreover, its handling and coupling to analytical equipment, such as HPLC, is facilitated. The Impedance technique (EIS) is a non-destructive electrochemical technique that allows an exhaustive characterisation of electrochemical systems, providing extensive information on what happens at the interfaces of these systems. Thanks to this characterisation it is possible to achieve a deep understanding of the processes happening in the microextraction systems by EME, allowing the improvement of these systems and predicting the optimal extraction conditions, reducing considerably the optimisation time and costs. In this work, microfluidic extraction platforms based on both LPME and EME techniques have been developed for their subsequent application to biological samples, achieving surprising results both in terms of extraction performance and in the almost complete reduction of the matrix effect. In addition, the development of new supported liquid membranes from natural origin brings these microfluidic extraction systems even closer to fully sustainable systems, which is currently so necessary. Finally, the incorporation of EIS into EME-adapted devices allows current systems to be enhanced, providing the opportunity to develop more sophisticated platforms that make it possible to overcome new challenges

Electromembrane extraction using deep eutectic solvents as the liquid membrane

In this work, we investigated for the first time hydrophobic deep eutectic solvents (DES) as supported liquid membrane (SLM) for electromembrane extraction (EME). Camphor, coumarin, DL-menthol, and thymol were used as non-ionic DES components. Different DESs compositions were tested, to study systematically the importance of hydrogen bonding and dispersion/aromatic interactions during mass transfer across the SLM. Unexpectedly, mixtures of coumarin and thymol were highly efficient SLMs, and provided exhaustive or near-exhaustive extraction of non-polar bases, non-polar acids, and polar bases. SLMs with such performance for both bases and acids, in a large polarity window, are not found in current literature. The SLMs were highly aromatic, very strong hydrogen bonding donors, and moderately strong hydrogen bonding acceptors. Aromatic (π type) interactions were apparently very important for transfer of bases, while hydrogen bonding were dominant for acids. EME of six polar basic drugs from plasma, with a coumarin and thymol mixture as SLM, and combined with UHPLC-MS/MS analysis, was evaluated to test the potential for analytical applications. Plasma was diluted 1:1 with phosphate buffer pH 2.0. Calibration curves were linear in the therapeutic ranges (0.970 < R2 < 0.999), recoveries ranged between 47 and 93%, and repeatability was within 1.6–10.7% RSD. The clean-up efficiency was excellent and no matrix effects from plasma were seen. Presence of trace levels of coumarin in the acceptor phase was however found to cause some ion enhancement. Based on the current work, we foresee more research on the use of DES in EME

Electromembrane extraction using deep eutectic solvents as the liquid membrane

In this work, we investigated for the first time hydrophobic deep eutectic solvents (DES) as supported liquid membrane (SLM) for electromembrane extraction (EME). Camphor, coumarin, DL-menthol, and thymol were used as non-ionic DES components. Different DESs compositions were tested, to study systematically the importance of hydrogen bonding and dispersion/aromatic interactions during mass transfer across the SLM. Unexpectedly, mixtures of coumarin and thymol were highly efficient SLMs, and provided exhaustive or near-exhaustive extraction of non-polar bases, non-polar acids, and polar bases. SLMs with such performance for both bases and acids, in a large polarity window, are not found in current literature. The SLMs were highly aromatic, very strong hydrogen bonding donors, and moderately strong hydrogen bonding acceptors. Aromatic (π type) interactions were apparently very important for transfer of bases, while hydrogen bonding were dominant for acids. EME of six polar basic drugs from plasma, with a coumarin and thymol mixture as SLM, and combined with UHPLC-MS/MS analysis, was evaluated to test the potential for analytical applications. Plasma was diluted 1:1 with phosphate buffer pH 2.0. Calibration curves were linear in the therapeutic ranges (0.970 < R2 < 0.999), recoveries ranged between 47 and 93%, and repeatability was within 1.6–10.7% RSD. The clean-up efficiency was excellent and no matrix effects from plasma were seen. Presence of trace levels of coumarin in the acceptor phase was however found to cause some ion enhancement. Based on the current work, we foresee more research on the use of DES in EME.Agencia de Gestió d’Ajusts Universitaris i the Recerca 2017-SGR-3