Mejora de las técnicas de microextracción mediante el diseño de nuevas modalidades asistidas por CO2

El proceso de medida químico se divide en tres etapas bien diferenciadas: (i) el conjunto de operaciones previas, que engloba la toma y el tratamiento de la muestra; (ii) la medida y transducción de la señal analítica; y (iii) la toma y análisis de los datos derivados. El tratamiento de la muestra tiene una incidencia decisiva en las propiedades analíticas. Influye en la exactitud (errores sistemáticos cometidos durante el proceso), precisión (errores aleatorios) y en las propiedades complementarias (rapidez, costes y factores humanos). También afecta a la selectividad (a través de la eliminación de interferentes) y sensibilidad (gracias a la preconcentración que se consigue de los analitos de interés) del proceso. La etapa de pretratamiento de muestra ideal debe ser simple, rápida y miniaturizada. Las técnicas de extracción en el pretratamiento de muestra se pueden clasificar en dos grandes familias en función de la naturaleza de la fase extractante: la extracción líquido-líquido (liquid-liquid extraction, LLE) y la extracción en fase sólida (solid phase extraction, SPE). Y a partir de estas, de acuerdo con las tendencias básicas de la Química Analítica: automatización, miniaturización y simplificación, surgen las técnicas de extracción miniaturizadas o de microextraccion, bien sean en fase sólida o líquida. Las llamadas técnicas de microextracción dispersivas son una novedosa alternativa que emplea bajos volúmenes de muestra y extractante. Presentan una elevada eficiencia, simplicidad operativa y elevados factores de preconcentración con un coste mínimo. El objetivo de esta modalidad es el aumento de la superficie de contacto de una fase extractante (ya sea sólida o líquida) con la muestra mediante la división de la primera en finas partículas o microgotas, generando una dispersión mediante un disolvente orgánico. Posteriormente, el extractante se recupera mediante centrifugación, filtración o campos mágneticos y se analiza mediante una técnica instrumental apropiada. De acuerdo a los principios de la Química Analítica Verde, las técnicas deben tender a minimizar el consumo de estos disolventes y el gasto energético derivado del uso de otros dispositivos. Por esta razón, el objetivo principal de la Tesis Doctoral es el desarrollo de modalidades de microextracción dispersivas, tanto en fase sólida como en fase líquida, mediante el empleo de dióxido de carbono como agente dispersante o como mediador de la solubilidad de nuevos disolventes conmutables

Effervescence-Assisted Microextraction—One Decade of Developments

Dispersive microextraction techniques are key in the analytical sample treatment context as they combine a favored thermodynamics and kinetics isolation of the target analytes from the sample matrix. The dispersion of the extractant in the form of tiny particles or drops, depending on the technique, into the sample enlarges the contact surface area between phases, thus enhancing the mass transference. This dispersion can be achieved by applying external energy sources, the use of chemicals, or the combination of both strategies. Effervescence-assisted microextraction emerged in 2011 as a new alternative in this context. The technique uses in situ-generated carbon dioxide as the disperser, and it has been successfully applied in the solid-phase and liquid-phase microextraction fields. This minireview explains the main fundamentals of the technique, its potential and the main developments reported

Artificial Multienzyme Scaffolds: Pursuing in Vitro Substrate Channeling with an Overview of Current Progress

Artificial multienzyme scaffolds are being developed for in vitro cascaded biocatalytic activity and, in particular, accessing substrate channeling. This review covers progress in this field over t..

Application of Switchable Hydrophobicity Solvents for Extraction of Emerging Contaminants in Wastewater Samples

In the present work, the effectiveness of switchable hydrophobicity solvents (SHSs) as extraction solvent (N,N-Dimethylcyclohexylamine (DMCA), N,N-Diethylethanamine (TEA), and N,N-Benzyldimethylamine (DMBA)) for a variety of emerging pollutants was evaluated. Different pharmaceutical products (nonsteroidal anti-inflammatory drugs (NSAIDs), hormones, and triclosan) were selected as target analytes, covering a range of hydrophobicity (LogP) of 3.1 to 5.2. The optimized procedure was used for the determination of the target pharmaceutical analytes in wastewater samples as model analytical problem. Absolute extraction recoveries were in the range of 51% to 103%. The presented method permits the determination of the target analytes at the low ng mL−1 level, ranging from 0.8 to 5.9 (except for Triclosan, 106 ng mL−1) with good precision (relative standard deviation lower than 6%) using high-pressure liquid chromatography (HPLC) combined with ultraviolet (DAD) and fluorescence (FLR) detection. The microextraction alternative resulted in a fast, simple, and green method for a wide variety of analytes in environmental water sample. The results suggest that this type of solvent turns out to be a great alternative for the determination of different analytes in relatively complex water samples

Use of nanomaterials in the pretreatment of water samples for environmental analysis

The challenge of providing clean drinking water is of enormous relevance in today’s human civilization, being essential for human consumption, but also for agriculture, livestock and several industrial applications. In addition to remediation strategies, the accurate monitoring of pollutants in water sup-plies, which most of the times are present at low concentrations, is a critical challenge. The usual low concentration of target analytes, the presence of in-terferents and the incompatibility of the sample matrix with instrumental techniques and detectors are the main reasons that renders sample preparation a relevant part of environmental monitoring strategies. The discovery and ap-plication of new nanomaterials allowed improvements on the pretreatment of water samples, with benefits in terms of speed, reliability and sensitivity in analysis. In this chapter, the use of nanomaterials in solid-phase extraction (SPE) protocols for water samples pretreatment for environmental monitoring is addressed. The most used nanomaterials, including metallic nanoparticles, metal organic frameworks, molecularly imprinted polymers, carbon-based nanomaterials, silica-based nanoparticles and nanocomposites are described, and their applications and advantages overviewed. Main gaps are identified and new directions on the field are suggested.publishe

Effervescence-Assisted Microextraction—One Decade of Developments

Dispersive microextraction techniques are key in the analytical sample treatment context as they combine a favored thermodynamics and kinetics isolation of the target analytes from the sample matrix. The dispersion of the extractant in the form of tiny particles or drops, depending on the technique, into the sample enlarges the contact surface area between phases, thus enhancing the mass transference. This dispersion can be achieved by applying external energy sources, the use of chemicals, or the combination of both strategies. Effervescence-assisted microextraction emerged in 2011 as a new alternative in this context. The technique uses in situ-generated carbon dioxide as the disperser, and it has been successfully applied in the solid-phase and liquid-phase microextraction fields. This minireview explains the main fundamentals of the technique, its potential and the main developments reported