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En este estudio nueve estudiantes de últimos cursos de grado y postgrado han desarrollado competencias emprendedoras mediante la mentorización y evaluación de grupos de estudiantes de primer curso. Cada estudiante de último curso o de postgrado ha llevado a cabo la mentorización de dos grupos de estudiantes en la realización de un trabajo bibliográfico en equipo desarrollado en la asignatura OBLII de primer curso del Grado en Química. Para llevar a cabo dicha mentorización los estudiantes-tutores han realizado entre 6 y 10 reuniones con el equipo durante el semestre y finalmente han evaluado una serie de competencias transversales que suponen el 12% de la calificación de la asignatura. En todo momento ha existido una comunicación entre el estudiante-tutor y el profesor de la asignatura que finalmente corrige el trabajo realizado por los estudiantes. Mediante este sistema, los estudiantes-tutores no solo han sido capaces de transmitir a los estudiantes de nuevo ingreso nuevas metodologías de trabajo, habilidades para la búsqueda de información o como gestionar el tiempo, sino que han desarrollado una serie de competencias transversales como la capacidad de liderar un equipo, la capacidad y espíritu crítico o la comunicación oral adquiriendo así competencias emprendedoras de gran utilidad para su incorporación al mundo laboral.

This work explores the multi-element capabilities of inductively coupled plasma - mass spectrometry with collision/reaction cell technology (CCT-ICP-MS) for the simultaneous determination of both spectrally interfered and non-interfered nuclides in wine samples using a single set of experimental conditions. The influence of the cell gas type (i.e. He, He+H2 and He+NH3), cell gas flow rate and sample pre-treatment (i.e. water dilution or acid digestion) on the background-equivalent concentration (BEC) of several nuclides covering the mass range from 7 to 238 u has been studied. Results obtained in this work show that, operating the collision/reaction cell with a compromise cell gas flow rate (i.e. 4 mL min−1) improves BEC values for interfered nuclides without a significant effect on the BECs for non-interfered nuclides, with the exception of the light elements Li and Be. Among the different cell gas mixtures tested, the use of He or He+H2 is preferred over He+NH3 because NH3 generates new spectral interferences. No significant influence of the sample pre-treatment methodology (i.e. dilution or digestion) on the multi-element capabilities of CCT-ICP-MS in the context of simultaneous analysis of interfered and non-interfered nuclides was observed. Nonetheless, sample dilution should be kept at minimum to ensure that light nuclides (e.g. Li and Be) could be quantified in wine. Finally, a direct 5-fold aqueous dilution is recommended for the simultaneous trace and ultra-trace determination of spectrally interfered and non-interfered elements in wine by means of CCT-ICP-MS. The use of the CCT is mandatory for interference-free ultra-trace determination of Ti and Cr. Only Be could not be determined when using the CCT due to a deteriorated limit of detection when compared to conventional ICP-MS.

En este estudio nueve estudiantes de últimos cursos de grado y postgrado han desarrollado competencias emprendedoras mediante la mentorización y evaluación de grupos de estudiantes de primer curso. Cada estudiante de último curso o de postgrado ha llevado a cabo la mentorización de dos grupos de estudiantes en la realización de un trabajo bibliográfico en equipo desarrollado en la asignatura OBLII de primer curso del Grado en Química. Para llevar a cabo dicha mentorización los estudiantes-tutores han realizado entre 6 y 10 reuniones con el equipo durante el semestre y finalmente han evaluado una serie de competencias transversales que suponen el 12% de la calificación de la asignatura. En todo momento ha existido una comunicación entre el estudiante-tutor y el profesor de la asignatura que finalmente corrige el trabajo realizado por los estudiantes. Mediante este sistema, los estudiantes-tutores no solo han sido capaces de transmitir a los estudiantes de nuevo ingreso nuevas metodologías de trabajo, búsqueda de información o gestión del tiempo, sino que han desarrollado una serie de competencias transversales como la capacidad de liderar un equipo, la capacidad y espíritu crítico o la comunicación oral adquiriendo así competencias emprendedoras de gran utilidad para su incorporación al mundo laboral.

Con la implantación del 4º curso del grado en Química, que se ha realizado en el presente curso académico, se han completado los cuatro cursos del grado. En la Facultad de Ciencias se han constituido ocho comisiones de semestre, en las que participan profesores de todos los departamentos que imparten docencia en la titulación y la Comisión de Grado, formada por los coordinadores de las comisiones de semestre que, a su vez, forman parte de una red docente para el seguimiento del grado. Desde estas comisiones se está realizando un intenso trabajo cooperativo cuyo objetivo es alcanzar una coherencia tanto en la distribución de contenidos, como en las metodologías docentes y de evaluación de las materias que componen el plan de estudios del Grado en Química de la Universidad de Alicante. La coordinación horizontal entre semestres de un mismo curso y la coordinación vertical entre cursos forman parte de las tareas que se desarrollan. Los resultados de este trabajo permiten identificar las deficiencias en el proceso de implantación y plantear posibles propuestas de mejora en la organización docente de la titulación.

The influence of the sample introduction system on the signals obtained with different tin compounds in inductively coupled plasma (ICP) based techniques, i.e., ICP atomic emission spectrometry (ICP–AES) and ICP mass spectrometry (ICP–MS) has been studied. Signals for test solutions prepared from four different tin compounds (i.e., tin tetrachloride, monobutyltin, dibutyltin and di-tert-butyltin) in different solvents (methanol 0.8% (w/w), i-propanol 0.8% (w/w) and various acid matrices) have been measured by ICP–AES and ICP–MS. The results demonstrate a noticeable influence of the volatility of the tin compounds on their signals measured with both techniques. Thus, in agreement with the compound volatility, the highest signals are obtained for tin tetrachloride followed by di-tert-butyltin/monobutyltin and dibutyltin. The sample introduction system exerts an important effect on the amount of solution loading the plasma and, hence, on the relative signals afforded by the tin compounds in ICP–based techniques. Thus, when working with a pneumatic concentric nebulizer, the use of spray chambers affording high solvent transport efficiency to the plasma (such as cyclonic and single pass) or high spray chamber temperatures is recommended to minimize the influence of the tin chemical compound. Nevertheless, even when using the conventional pneumatic nebulizer coupled to the best spray chamber design (i.e., a single pass spray chamber), signals obtained for di-tert-butyltin/monobutyltin and dibutyltin are still around 10% and 30% lower than the corresponding signal for tin tetrachloride, respectively. When operating with a pneumatic microconcentric nebulizer coupled to a 50 °C-thermostated cinnabar spray chamber, all studied organotin compounds provided similar emission signals although about 60% lower than those obtained for tin tetrachloride. The use of an ultrasonic nebulizer coupled to a desolvation device provides the largest differences in the emission signals, among

A systematic study on the influence of carbon on the signal of a large number of hard-to-ionize elements (i.e. B, Be, P, S, Zn, As, Se, Pd, Cd, Sb, I, Te, Os, Ir, Pt, Au, and Hg) in inductively coupled plasma–mass spectrometry has been carried out. To this end, carbon matrix effects have been evaluated considering different plasma parameters (i.e. nebulizer gas flow rate, r.f. power and sample uptake rate), sample introduction systems, concentration and type of carbon matrix (i.e. glycerol, citric acid, potassium citrate and ammonium carbonate) and type of mass spectrometer (i.e. quadrupole filter vs. double-focusing sector field mass spectrometer). Experimental results show that P, As, Se, Sb, Te, I, Au and Hg sensitivities are always higher for carbon-containing solutions than those obtained without carbon. The other hard-to-ionize elements (Be, B, S, Zn, Pd, Cd, Os, Ir and Pt) show no matrix effect, signal enhancement or signal suppression depending on the experimental conditions selected. The matrix effects caused by the presence of carbon are explained by changes in the plasma characteristics and the corresponding changes in ion distribution in the plasma (as reflected in the signal behavior plot, i.e. the signal intensity as a function of the nebulizer gas flow rate). However, the matrix effects for P, As, Se, Sb, Te, I, Au and Hg are also related to an increase in analyte ion population caused as a result of charge transfer reactions involving carbon-containing charged species in the plasma. The predominant specie is C+, but other species such as CO+, CO2+, C2+ and ArC+ could also play a role. Theoretical data suggest that B, Be, S, Pd, Cd, Os, Ir and Pt could also be involved in carbon based charge transfer reactions, but no experimental evidence substantiating this view has been found.

Proceso de preparación de una disolución de patrón primario.

Pesada de sólidos por método indirecto.

Procedimiento volumetría.

Preparación de un filtro de pliegues.

Filtrado de disoluciones.

Procedimiento de filtrado a vacío empleando un matraz kitasatos

Proceso de calentamiento de un tubo de ensayo

Proceso de preparación de una disolución no patrón primario.

Descripción del método de análisis de Espectrometría de Absorción Atómica por Atomización Electrotérmica (Cámara de Grafito).

Descripción del proceso de pesada directa

A new fully microwave-assisted liquid sample introduction system (MASIS) is presented and evaluated in Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The device employs a single TM010 microwave cavity for the simultaneous aerosol generation and desolvation. The different experimental requirements of both physical processes demand a careful system design and a judicious selection of the experimental conditions. The behavior of the MASIS depends on the: (i) microwave power; (ii) nebulizer nozzle inner diameter; (iii) sample uptake rate; and, (iv) matrix nature (i.e. acids, salts) and concentration. Thus, optimum operating conditions are obtained when increasing the microwave power, the matrix concentration and the sample uptake rate as well as when decreasing the nebulizer nozzle inner diameter. The analytical figures of merit afforded by the MASIS in ICP-AES are compared to those obtained with: (1) a pneumatic concentric nebulizer coupled to a cyclonic spray chamber (CS); (2) a microwave thermal nebulizer (MWTN) coupled to a cyclonic spray chamber; and (3) a pneumatic nebulizer coupled to a microwave desolvation system (MWDS). MASIS provides limits of detection up to 50 times lower than those obtained with the CS and up to 8 times lower than those with the MWTN and MWDS. No significant difference in the signal precision between the different devices tested is observed (i.e. 2–5%). Regarding the wash-out times, both MASIS and MWDS show the highest values of this parameter (i.e. 70 s) due to their higher inner volume. Wash-out time values for both MWTN and CS are lower than 30 s.

The determination of Pb, Se and As in wine has a great interest due to health risks and legal requirements. To perform the analysis of wine, two considerations must be taken into account: (i) the low concentration level of the analytes; and (ii) the risk of interferences due to wine matrixcomponents. The goal of this work is to evaluate electrothermal vaporization (ETV)sample introduction for ultratrace determination of Pb, Se and As in wine samples by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained with ETV-ICP-MS were compared to those obtained with conventional liquid sample introduction in ICP-MS and electrothermal atomic absorption spectrometry (ETAAS). Analytical figures of merit of ETV sample introduction strongly depend on the amount of wine sample, on the modifier nature (i.e. Pd, ascorbic acid or citric acid) and concentration and on the temperature program. Wine matrix components exert a great influence on analyte transport efficiency. Due to this fact, the analysis of wine cannot be performed by means of external calibration but the standard addition methodology should be used. The determination of Pb and Se in wine by ETV-ICP-MS provides similar results as conventional liquid sample introduction ICP-MS. For As, the concentration values obtained with ETV sample introduction were between two and four times lower than with the conventional system. These differences are related to the lower intensity of polyatomic interferences obtained for ETV sample introduction when compared to the conventional system. Finally, no differences for Pb determination were observed between ETV sample introduction and ETAAS. Unfortunately, the limits of detection for As and Se in ETAAS were not low enough to quantify these elements in the wine samples tested.

Elemental wine analysis is often required from a nutritional, toxicological, origin and authenticity point of view. Inductively coupled plasma based techniques are usually employed for this analysis because of their multi-elemental capabilities and good limits of detection. However, the accurate analysis of wine samples strongly depends on their matrix composition (i.e. salts, ethanol, organic acids) since they lead to both spectral and non-spectral interferences. To mitigate ethanol (up to 10% w/w) related matrix effects in inductively coupled plasma atomic emission spectrometry (ICP-AES), a microwave-based desolvation system (MWDS) can be successfully employed. This finding suggests that the MWDS could be employed for elemental wine analysis. The goal of this work is to evaluate the applicability of the MWDS for elemental wine analysis in ICP-AES and inductively coupled plasma mass spectrometry (ICP-MS). For the sake of comparison a conventional sample introduction system (i.e. pneumatic nebulizer attached to a spray chamber) was employed. Matrix effects, precision, accuracy and analysis throughput have been selected as comparison criteria. For ICP-AES measurements, wine samples can be directly analyzed without any sample treatment (i.e. sample dilution or digestion) using pure aqueous standards although internal standardization (IS) (i.e. Sc) is required. The behaviour of the MWDS operating with organic solutions in ICP-MS has been characterized for the first time. In this technique the MWDS has shown its efficiency to mitigate ethanol related matrix effects up to concentrations of 1% (w/w). Therefore, wine samples must be diluted to reduce the ethanol concentration up to this value. The results obtained have shown that the MWDS is a powerful device for the elemental analysis of wine samples in both ICP-AES and ICP-MS. In general, the MWDS has some attractive advantages for elemental wine analysis when compared to a conventional sample introduction system such as

A re-designed microwave-based thermal nebulizer (MWTN) that overcomes all the drawbacks shown by previous prototypes (i.e. lack of robustness, poor heating efficiency) is presented. The new device employs an optimized TM010 cavity and nozzle design. MWTN performance was evaluated in inductively coupled plasma atomic emission spectrometry ICP-AES) and compared to that provided by a concentric pneumatic nebulizer. Current MWTN design improves sample heating efficiency and system robustness. As a consequence, a 10 times lower matrix concentration than previous designs can be employed. The minimum inorganic (i.e. acids and salts) and organic (i.e. alcohols) concentrations required to nebulize are 0.25 and 40% w/w, respectively. The influence of microwave power (180–290 W), matrix nature (acids, salts and organics), sample uptake rate (0.9–1.8 mL/min) and nebulizer critical dimensions, such as nozzle and PTFE capillary internal diameter (150–300 and 300–800 mm) and PTFE capillary length (50–150 cm) on the behaviour of the MWTN was studied. Optimum operating conditions for this nebulizer are obtained employing high microwave powers, matrix concentration and sample uptake rate, as well as nozzle and PTFE capillary with a narrow internal diameter. Although the MWTN behavior depends on the samples physical properties, aerosol drop size distributions and analyte transport rate for inorganic solutions above 2% w/w are independent of matrix composition. Current MWTN shows higher sensitivity and lower limits of detection (up to 12 times for acid solutions) than a conventional pneumatic nebulizer. The performance of the new prototype has been evaluated analyzing a certified bovine liver (CRM 185 R) and a spirit sample. Experimental results indicate that MWTN can be employed successfully for routine sample analysis.

The goal of this work is to evaluate ETV sample introduction for the determination of ultratrace elements in wine samples by ICP-MS. Temperature program, modifier selection and concentration and calibration technique have been studied. Preliminary results show that ETV can be successfully used to perform elemental wine analysis of wine. Nonetheless, analytical results critically depend on the calibration technique employed.

The aim of this work is to study the carbon related non-spectroscopic matrix effects in ICP-AES. To this end, the effect of some experimental conditions (matrix nature, sample uptake rate, r.f. plasma power and sample introduction system) on the behaviour of a total of 15 elements and several emission lines covering a wide range of energy values (atomic and ionic) in ICP-AES has been studied. Results show a clear effect related to the amount of carbon present in the plasma. Thus, the presence of carbon in the plasma gives rise to a decrease in most of the emission lines tested, with the exception of As and Se. For these elements, the emission signal increases when an increasing the amount of carbon is reaching the plasma. Depending on the experimental conditions employed, the emission signals for As and Se are up to 25% higher than those obtained with pure aqueous solutions. These findings have been applied to the analysis of a certified sample of Se-enriched yeast (SELM-1).

In Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), it has been observed that the emission intensity of some atomic lines is enhanced or depressed by the presence of carbon in the matrix. The goal of this work was to investigate the origin and magnitude of the carbon-related matrix effects in ICP-AES. To this end, the influence of the carbon concentration and source (i.e. glycerol, citric acid and potassium hydrogen phthalate), the experimental conditions and sample introduction system on the aerosol characteristics and transport, plasma excitation conditions and the emission intensity of several atomic and ionic lines of a total of 15 elements has been studied. Results indicate that carbon related matrix effects do not depend on the carbon source and they become more severe when the amount of carbon loaded into the plasma increases, i.e., when using: (i) carbon concentrations higher than 5 g L−1; (ii) high sample uptake rates; and (iii) efficient sample introduction systems. Thus, when introducing carbon into the plasma, the emission intensity of atomic lines with excitation energies below 6 eV is depressed (up to 15%) whereas the emission intensity of atomic lines of higher excitation energies (i.e. As and Se) are enhanced (up to 30%). The emission intensity of the ionic lines is not affected by the presence of carbon. The origin of the carbon-related interferences on the emission intensity of atomic lines is related to changes in the line excitation mechanism since the carbon containing solutions show the same aerosol characteristics and transport efficiencies as the corresponding aqueous solutions. Based on the previous findings, a calibration approach for the accurate determination of Se in a Se-enriched yeast certified material (SELM-1) has been proposed.

The European Standard EN 71/3 and the Directive 88/378/CEE limit the migration of some heavy metals (As, Ba, Cr, Cd, Hg, Pb, Sb and Se) and their daily bioavailability in plastics used in toy industry. Other Draft Standard Projects, also based in the later directive, limit the same parameters in plastics used for childcare articles. Previous interlaboratory studies have shown that the migration analyses of heavy metals using European Standard lack of accuracy and reproducibility. In addition, analyte concentration in these materials is too close, or even lower, than the detection limits (LOD) of the analytical techniques recommended (i.e. Flame, Hydride Generation and Cold Vapour Atomic Absorption Spectrometry). The aim of this work is to evaluate the behaviour of different sample introduction devices for the elemental polymer analysis by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). To this end, the limits of quantification (LOQs), defined as 3 times the LODs, obtained with the different devices were compared with the maximum concentration allowed by the CE Standard in the solution obtained after sample microwave digestion treatment (MCA).

In this work, a new sample introduction system fully based on MW radiation (MWSIS) has been developed and characterized in ICP-AES. Variables affecting the MWSIS behaviour are: MW power, matrix nature (i.e. acids, salts, organic solvents), sample uptake rate and nozzle diameter. New sample introduction system gives rise to sensitivities and LODs between 10 and 20 times better than a conventional sample introduction system.

A microwave assisted sample introduction system based on the use of a TM010 cavity (MWDS2) has been employed for the introduction of 10% w/w organic solvent solutions in inductively coupled plasma atomic emission spectrometry (ICP-AES). Ethanol, propan-2-ol, formic and acetic acids have been used. Firstly, the effect of the incident microwave power and the sample uptake rate on the emission signal was evaluated. For all matrices tested, the higher emission signals were obtained when operating at the highest microwave power (i.e., 290 W) and sample uptake rate (400 mL/min). Results with the MWDS2 were compared with those afforded by a desolvation system based on the use of a domestic microwave oven (MWDS) and by a conventional sample introduction system (CS). The MWDS2 provides the highest emission signals (up to 7 and 17 times higher than those with the MWDS and the CS, respectively). As regards the matrix effects originated by the organic solutions, results demonstrate that the use of a microwave-based sample introduction system, mainly the MWDS2, affords a noticeable reduction in the matrix effects originated by the use of organic solvent solutions in ICP-AES with a conventional sample introduction system. This behaviour can be explained by taking into account the solution transport rates afforded by the different sample introduction systems. For all the analytical lines and matrices tested and operating at 400 mL/min, the MWDS2 gives rise to signal values that are, on average, 1.2 times the signal obtained with water. For the MWDS and the CS, this factor takes values of 1.6 and 2.0, respectively. Transient matrix effects have been observed operating with the MWDS2 when switching between water and an organic matrix solution. These transient effects result in a drift time about 4.5 times higher than those with a CS.

A new microwave assisted desolvation system based on the use of a TM010 cavity (MWDS2) has been developed and evaluated in plasma based analytical techniques: inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The new design overcomes the main experimental drawbacks shown by previous designs based on the use of domestic ovens: (i) lack of control on microwave generation and application; and (ii) inappropriate MW cavity characteristics. The evaluation has been performed in terms of the effect of the incident microwave power and the sample uptake rate and the results obtained has been compared with those afforded by a conventional sample introduction system (nebulizer and double pass spray chamber) and a desolvation system based on the use of a domestic microwave oven (MWDS). The new MWDS2 give rise to higher analytical signals and lower limits of detection and stabilization times (2–3 times) than those obtained with the MWDS in ICP-AES and ICP-MS.

El análisis elemental de muestras con elevado contenido en disolventes orgánicos representa un problema de difícil solución en Espectrometría Atómica con fuente de ionización de Plasma Acoplado Inductivamente (ICP-AES). La tolerancia reducida, por parte del plasma, a la carga de disolvente desaconseja el análisis directo de este tipo de muestras. La forma más usual de evitar los problemas asociados con este tipo de análisis es mediante el empleo de sistemas de introducción de muestra provistos de un sistema de desolvatación. En la bibliografía se han descrito distintos sistemas de desolvatación para su uso en ICP-AES. Recientemente se ha propuesto un sistema basado en la absorción de radiación de microondas (SDMW1). El principal problema de este sistema es el escaso control que se ejerce sobre la calefacción del aerosol. El objetivo del presente trabajo consiste en: (i) caracterizar un nuevo diseño de desolvatador basado en la calefacción por microondas (SDMW2); y, (ii) evaluar la aplicación de las microondas a la desolvatación de disoluciones orgánicas en ICP-AES. Los resultados se han obtenido empleando matrices de diferente naturaleza (agua, alcoholes y ácidos orgánicos). Además del SDMW2, se han empleado un sistema convencional de introducción de muestras (SC) y el diseño previo del desolvatador (SDMW1). Los resultados obtenidos muestran como el SDMW2 permite una mayor eficiencia y control sobre el proceso de calefacción que conduce a una mejora de la sensibilidad respecto a los otros dos sistemas de introducción de muestra. En cuanto a los efectos de matriz con disoluciones orgánicas se observa que dependen fuertemente del sistema de introducción de muestra elegido. La utilización de los sistemas de desolvatación por microondas permiten reducir la magnitud de éste efecto. Para las diferentes disoluciones orgánicas estudiadas (ácidos orgánicos y alcoholes) el efecto de matriz es mínimo para el SDMW2. Una desventaja del uso de los sistemas por microondas es el in