This review focuses on the combination of elemental detection techniques with liquid-phase microextraction (LPME), namely, single drop microextraction, hollow fiber based liquid-phase microextraction, dispersive liquid-liquid microextraction, and related techniques. General features of different microextraction procedures, historical overview and automation of LPME are described and compared, along with examples of new developments and applications presented to demonstrate its potential for trace and ultra-trace metal analysis. Furthermore, potential applications and an outlook on the combination of LPME and elemental detection techniques for inorganic analysis are presented. ; The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project n. CTQ2016-79991-R) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).
Magnetic deep eutectic solvents (MDESs) have recently produced a torrent of pioneering applications in endless areas of sample preparation. By including a magnetic nanomaterial (e.g., magnetic nanoparticles) or a paramagnetic anion (e.g., [FeCl4]-) in their structure, MDESs exhibit a strong response under the application of an external magnetic field. Furthermore, the use of MDESs, as a sorbent or solvent in extraction techniques, have been scarcely employed to develop green analytical methods, characterized by the avoid of time-consuming steps and the use of toxic organic solvents, as well as the application of small amounts of MDESs, for the determination of organic and inorganic contaminants, drugs, proteins, among others in environmental, food and biological matrices. This review highlights the application of MDESs in sample preparation in analytical chemistry. Challenges and future outlooks of new MDESs are also presented. ; The authors would like to thank the Regional Government of Valencia (PROMETEO/2018/087) for the financial support. The authors extend their appreciation to Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T). This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society.
Zeolites are ordered crystalline materials with a promising performance for a wide range of applications such as catalysis, petrochemistry, environmental remediation, and medicine, but have scarcely been evaluated in Analytical Chemistry. Their unique and fascinating properties such as their high surface area, high adsorption capacity and molecular selectivity, chemical and thermal stability, ion-exchange capacity, low cost extraction and synthesis, and their easy modification, which provides a wide range of zeolite-based materials, make zeolites potential sorbents for extraction procedures. Therefore, in this review, we provide an overview of the current status of zeolites and zeolite-based materials used in extraction and microextraction techniques with reference to recent applications and highlight some of the novel advances. ; The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project no. CTQ2016-79991-R) for financial support. P. Baile also thanks the Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).
[cat] A causa de l'augment de l'entrada de contaminants en el medi aquàtic, el control de l'aigua és essencial. En aquest sentit, els governs han augmentat el control de l'aigua a través de regulacions més estrictes. Pel que és important desenvolupar mètodes analítics eficients en termes de cost, precisió, freqüència d'anàlisi i impacte ambiental per controlar les emissions de contaminants i així verificar el compliment de les normes definides. No obstant això, les anàlisis mediambientals plantegen algunes dificultats a causa de la complexitat de les matrius de les mostres, ja que en general els analits d'interès són a nivell de traces i hi ha una àmplia varietat de possibles interferents, fent gairebé obligatòria una etapa de pretractament de la mostra abans de la detecció. Les noves tendències es centren en l'ús de tècniques de microextracció, com ara la microextracció en fase sòlida (SPME) i la microextracció líquid-líquid dispersiva (DLLME). No obstant això, les etapes de pretractament són llargues i impliquen un gran consum de reactius i mostra quan es duen a terme de forma manual. Així, l'automatització del pretractament de la mostra té un paper important per aconseguir mètodes analítics eficients i ràpids. Per tant, l'objectiu principal d'aquesta tesi ha estat desenvolupar diferents metodologies basades en tècniques d'anàlisi en flux per a la determinació de paràmetres d'interès ambiental. Aquestes metodologies es basen en la implementació de tècniques de microextracció, és a dir SPME i DLLME, en sistemes en flux, en particular utilitzant sistemes d'anàlisi per injecció seqüencial, sistemes d'anàlisi per injecció en flux multixeringa i lab-on-valve. L'ús de tècniques de detecció espectrofotomètriques i fluorimètriques ha permès el desenvolupament d'analitzadors totalment automàtics. Així, el potencial de les tècniques d'anàlisi en flux per implementar diferents tècniques de pretractament de la mostra queda demostrat en aquesta tesi amb el desenvolupament de set sistemes analítics automàtics per determinar ferro, alumini, tensioactius aniònics i catiònics, i filtres UV, aplicats a mostres d'aigua ambiental. Tots els analitzadors desenvolupats han demostrat la gran versatilitat de les tècniques d'anàlisi en flux en el seu acoblament a una gran varietat de tècniques de detecció i pretractaments. A més, l'ús de tècniques d'anàlisi en flux per automatitzar els mètodes analítics desenvolupats ha aportat gran robustesa, simplicitat i estabilitat la qual cosa s'ha traduït en resultats precisos i exactes, juntament amb l'estalvi de temps i reactius, una major freqüència de mostreig, una mínima manipulació de la mostra i reactius per part de l'analista, i un menor impacte ambiental per anàlisi a causa de la reducció dels residus generats. ; [spa] Debido al aumento de la entrada de contaminantes en el medio acuático, el control del agua es esencial. En este sentido, los gobiernos han aumentado el control del agua a través de regulaciones más estrictas. Por lo que es importante desarrollar métodos analíticos eficientes en términos de coste, precisión, frecuencia de análisis e impacto ambiental para controlar las emisiones de contaminantes y así verificar el cumplimiento de las normas definidas. Sin embargo, los análisis medioambientales plantean algunas dificultades debido a la complejidad de las matrices de las muestras, ya que por lo general los analitos de interés están a nivel de trazas y hay una amplia variedad de posibles interferentes, haciendo casi obligatoria una etapa de pretratamiento de la muestra antes de la detección. Las nuevas tendencias se centran en el uso de técnicas de microextracción, tales como la microextracción en fase sólida (SPME) y la microextracción liquido-líquido dispersiva (DLLME). No obstante, las etapas de pretratamiento son largas e implican un gran consumo de reactivos y muestra cuando se llevan a cabo de forma manual. Así, la automatización del pretratamiento de la muestra juega un papel importante para lograr métodos analíticos eficientes y rápidos. Por tanto, el objetivo principal de ésta tesis ha sido desarrollar diferentes metodologías basadas en técnicas de análisis en flujo para la determinación de parámetros de interés ambiental. Estas metodologías se basan en la implementación de técnicas de microextracción, es decir SPME y DLLME, en sistemas en flujo, en particular utilizando sistemas de análisis por inyección secuencial, sistemas de análisis por inyección en flujo multijeringa y lab-on-valve. El uso de técnicas de detección espectrofotométricas y fluorimétricas ha permitido el desarrollo de analizadores totalmente automáticos. Así, el potencial de las técnicas de análisis en flujo para implementar diferentes técnicas de pretratamiento de la muestra queda demostrado en esta tesis con el desarrollo de siete sistemas analíticos automáticos para determinar hierro, aluminio, tensioactivos aniónicos y catiónicos, y filtros UV, aplicados a muestras de agua ambiental. Todos los analizadores desarrollados han demostrado la gran versatilidad de las técnicas de análisis en flujo en su acoplamiento a una gran variedad de técnicas de detección y pretratamientos. Además, el uso de técnicas de análisis en flujo para automatizar los métodos analíticos desarrollados ha aportado gran robustez, simplicidad y estabilidad lo cual se ha traducido en resultados precisos y exactos, junto con el ahorro de tiempo y reactivos, una mayor frecuencia de muestreo, una mínima manipulación de la muestra y reactivos por parte del analista, y un menor impacto ambiental por análisis debido a la reducción de los residuos generados. ; [eng] Water monitoring has become essential owing to the increasing income of contaminants into the aquatic environment. In this sense, governments have increased water control through tighter regulations. Hence, it is important to develop efficient analytical methods in terms of cost, precision, throughput and environmental impact to control pollutant releases and verify compliance with respect to defined regulations. However, environmental analysis poses some difficulties due to matrix complexity, since the analytes of interest are usually at trace levels and there is a wide variety of potential interferences, making almost mandatory the sample pretreatment prior detection. New trends are focused in the use of microextraction techniques, such as solid phase microextraction (SPME) and dispersive liquid-liquid microextraction (DLLME). Nonetheless, pretreatment steps are time consuming and involve a large consumption of reagents and sample when carried out in a manual approach. Thus, automation of sample pretreatment plays a major role in order to achieve efficient and fast analytical methods. Therefore, the main objective of this thesis was to develop different automatic analytical flow-based methodologies for the determination of parameters of environmental interest. They are based on the implementation of microextraction techniques, i.e. SPME and DLLME, in flow based systems, in particular exploiting sequential injection analysis, multisyringe flow injection analysis and lab-on-valve. Spectrophotometric and fluorimetric detection techniques were used allowing the development of fully automated analyzers. Thus, in this thesis the potential of flow analysis techniques to accommodate a variety of pretreatment techniques is proven by the development of seven automated analytical systems to determine iron, aluminium, anionic and cationic surfactants and UV filters, applied to environmental water samples. All the developed analyzers have demonstrated the versatility of flow analysis techniques to accommodate a plethora of pretreatment and detection techniques. Furthermore the use of flow analysis techniques to automate the present analytical methods achieving maximal robustness, simplicity and stability has resulted in precise and accurate results, together with time and reagents saving, and therefore higher sample frequency, minimal handling of sample and reagents, and a lower environmental impact per analysis due to reduced waste production.
Vortex-assisted liquid–liquid microextraction (VALLME) coupled with high-performance liquid chromatography (HPLC) is proposed here for the rapid determination of octanol–water partitioning coefficients (Kow). VALLME uses vortex agitation, a mild emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2 min were enough to achieve equilibrium conditions between the octanolic and aqueous phases. Upon equilibration, separation was achieved using centrifugation and the octanolic microdrop was collected and analyzed in a HPLC system. Six model compounds with log Kow values ranging between ∼0.5 and 3.5 were used during the present investigations. The proposed method produced log Kow values that were consistent with previously published values and the recorded uncertainty was well within the acceptable log unit range. Overall, the key features of the proposed Kow determination procedure comprised speed, reliability, simplicity, low cost and minimal solvent consumption. ; EP is grateful to the Region of Crete (Perifereia Kritis) for funding. Financial support from the Spanish Government (Project CTQ2011-23968) is also acknowledged. I.P.R. also thanks "Caja de Ahorros del Mediterraneo (CAM)" for his predoctoral grant and financial support.
Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal for the analysis of liquid samples, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the performances of LIBS towards the analysis of solutions. Among the various strategies, the most promising and versatile appears to be Thin Film Microextraction (TFME) using carbon-based adsorbents. Another sample pre-treatment procedure, Nanoparticle-Enhanced LIBS (NELIBS), has gained significant interest due to its relative simplicity and effectiveness. This methodology uses a deposition of silver nanoparticles (AgNPs) on the sample to greatly increase the emission of the LIBS plasma. In this work, we investigate for the first time the possibility of combining TFME and NELIBS. We developed TFME supports by depositing an aqueous graphene nano-sheets (aq-GRA) prepared by Pulsed Laser Ablation in Liquid (PLAL) on a glass substrate. The preparation of the supports was optimized with regards to the substrate nature, deposition method, sorbent volume and drying method. Then, the TFME supports were tested for the extraction of Chromium from aqueous solution at different extraction times and analyte concentration. Subsequently, the TFME supports were treated with a deposition of silver nanoparticles (AgNP) to test the feasibility of the NELIBS approach. We observed an enhancement in the emission lines of Cr when the AgNPs were applied, as well as a lower estimated LOD value when compared to plain graphene TFME supports. ; M. Hidalgo is grateful to Ministerio de Economía, Industria y Competitividad [CTQ2016-79991-R] and Conselleria de Educación, Investigación, Cultura y Deporte (Regional Government of Valencia, Spain) [PROMETEO/2018/087] for the financial support.
Gas chromatography with MS detection was applied for simultaneous determination of six of the most toxic organotin compounds (OTs): monobutyltin, dibutyltin, tributyltin, monophenyltin, diphenyltin, triphenyltin. Headspace single drop microextraction (HS-SDME) in Ionic liquids (ILs) was proposed as Green alternative to the traditional one. Three different ILs ([C8MIM][PF6]; [C6MIM][PF6]) and [C4MIM][PF6]) were evaluated as a collector phase. The first one was found as the most appropriate for a group microextraction of the tested OTs. Analytes were evaporated from the IL microdrop by means of thermal desorption. ILs possess some advantages as an extraction phase in comparison with traditionally used organic solvents. They are more stable during the analytical process and are considered as environmentally friendly compounds. Moreover HS-SDME procedure was performed in a single drop of only 5μl IL. The time needed for the extraction was proved to be only 20 min. Therefore the proposed method could be related to the Green chemistry methods. ; The current study has been financially supported by: NSF of Bulgaria (Project DO 02-70 (GAMA)); EC 7FP Project 245588 (BioSupport); MICINN of Spain (Project CTQ2008-06730-C02-01) and Regional Government of Valencia (Project ACOMP2010/047). LG thanks Erasmus program and Ministry of Education for her fellowship. IPR also thanks "Caja de Ahorros del Mediterraneo (CAM)" for his Ph.D fellowship.
11 páginas, 8 figuras, 5 tablas ; Headspace solid-phase microextraction (HS-SPME) is proposed for isolating and determining the headspace volatiles formed during oxidation of fish-oil-in-water emulsions. Three different fiber coatings were tested and compared for sensitivity and reproducibility. A carboxen/polydimethylsiloxane (CAR-PDMS) fiber coating was found to be the most suitable for the analysis of emulsion volatiles. The main factors affecting the microextraction process on CAR-PDMS were then evaluated by a factorial design: amount of sample, time and temperature of extraction and stirring. The incubation of 0.5 g of emulsion at 60 °C during 30 min leads to the most effective extraction of volatiles associated with lipid oxidation of fish oil emulsions. The HS-SPME method coupled with GC–MS allowed the qualitative and quantitative analysis of the volatiles derived from oxidation of real fishoil enriched foods such as milk and mayonnaise. The method here proposed is very fast and simple and yields high sensitivity, with good repeatability for all target compounds. ; This work was performed within the research project PPQ2003-06602-C04-03 and the Integrated Research Project SEAFOODplus, contract No FOOD-CT-2004-506359. The financing of this work by the Spanish Ministry of Science and Technology and the European Union is gratefully acknowledged. ; Peer reviewed
5 tablas, 5 figuras ; A procedure for the determination of volatile compounds derived from lipid oxidation of fish muscle samples is presented. Analytes are concentrated on a solid-phase microextraction fiber employed in the headspace mode (HS-SPME), and selectively determined using gas chromatography in combination with mass spectrometry (GC–MS). The influence of several parameters on the efficiency of microextraction such as type of fiber, volume of sample, time, temperature, salting-out effect and stirring was systematically investigated. A saline extraction of fish muscle followed by incubation on a Carboxen-polydimethylsiloxane fiber during 30 min at 60 °C gave the most effective and accurate extraction of the analytes. Quantification of them was performed by MS in the selected ion monitoring mode and by the internal standard method. Satisfactory linearity, repeatability and quantification limits were achieved under these conditions. The method was applied to the determination of the volatile compounds associated to oxidation of Atlantic horse mackerel (Trachurus trachurus) minced muscle and excellent correlations were obtained with chemical indexes for monitoring lipid oxidation as peroxide value and thiobarbituric acid reactive substances. This combined technique is fast, simple, sensitive, inexpensive and useful to monitor target compounds associated to fish rancidity as 1-penten-3-ol, 2,3-pentanedione or 1-octen-3-ol ; This work was performed within the research project PPQ2003-06602-C04-03 and the Integrated Research Project SEAFOODplus, contract No FOOD-CT-2004-506359. The financing of this work by the Spanish Ministry of Science and Technology and the European Union is gratefully acknowledged ; Peer reviewed
A new method for simultaneous extraction and quantification of 6 nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) and 16 parent polycyclic aromatic hydrocarbons (PAHs) in water matrices was optimized and validated. The extraction procedure was based on dispersive liquid-liquid microextraction technique, followed by gas chromatography-mass detection. The optimum conditions of extraction (volume of the extraction solvent, dispersive solvents and amount of salt) were selected using central composite design. The best results were found by using 200 μL of acetonitrile as dispersive solvent, 60 μL of chloroform as extraction solvent, and 10% (w/v) NaCl. Excellent linearity was observed in the range of 10–150 ng L−1 with correlation coefficients (r2) ranging between 0.9996 and 0.9999 for nitro-PAHs and in the range of 5–150 ng L−1 with r2 ranging from 0.9998 to 1.000 for PAHs. The limits of detection for the nitro-PAHs studied ranged from 0.82 to 3.37 ng L−1, whereas for PAHs ranged from 0.62 to 3.48 ng L−1. The intra- and inter-day precisions for nitro-PAHs were in the range of 0.45 to 19.54% and 0.43 to 19.62%, respectively, and for PAHs ranged between 0.45 to 17.42% and 0.38 to 18.97%, respectively. The proposed method was successfully applied in analyses of groundwater, sea, rain water and river water, being appropriate for routine analyses. ; This work received financial support from the European Union (FEDER funds POCI/01/0145/FEDER/007265) and National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/QUI/50006/2013. One of the authors (A. Melo) wishes to thank the Fundação Ciência Tecnologia, grant SFRH/BPD/86898/2012. ; info:eu-repo/semantics/publishedVersion
Emerging environmental pollutants are becoming a global concern, since the acceptable concentrations are currently not set by legislation in EU or elsewhere. Benzotriazoles are an important group of emerging pollutants found in low µg/L concentrations, entering the environment through wastewater treatment facilities due to their insufficient removal, and through industrial and other use. Two new dispersive liquid-liquid microextraction (DLLME) methods were developed for the extraction of hydrophilic and hydrophobic benzotriazoles from environmental waters. Liquid chromatographic method coupled to tandem mass spectrometric detection (LC-MS/MS) was developed and validated for surface water. Validation parameters were satisfactory and the overall DLLME-LC-MS/MS method was found to be applicable to analysis of the chosen analytes in environmental waters. It was used to determine benzotriazoles in surface water and wastewater from a municipal wastewater treatment plant. In surface waters, concentration was below the limit of detection, while concentrations determined in wastewater were estimated between 2.7 and 12.0 mg/L.
