Artículos (Química Analítica)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10909

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A chemical speciation of trace metals for fine urban particles
(Elsevier, 2002) Fernández Espinosa, Antonio José; Ternero Rodríguez, Miguel; Barragán de la Rosa, Francisco José; Jiménez Sánchez, Juan Carlos; Universidad de Sevilla. Departamento de Química Analítica; Junta de Andalucía
The chemical speciation of 11 metals in aerosols has been studied in 12 areas of the city of Seville (Spain). Urban particles were collected with a high-volume sampling system equipped with a cascade impactor, which effectively separates the particulate matter into six size ranges. Forty-one samples were collected in the spring of 1996. The chemical speciation was studied in the finest particles of the impactor system (<0.61 μm), those that can penetrate into the alveolar region of the lung. This speciation scheme is specific for urban particles and consisted of four fractions: 1. soluble and exchangeable metals; 2. carbonates, oxides and reducible metals; 3. bound to organic matter, oxidisable and sulphidic metals; and 4. residual metals. The sample extractions were analysed for 11 metals by inductively coupled plasma atomic emission spectrometry (ICP-AES). The chemical speciation of metals showed that the metals with highest percentages in the different fractions are vanadium (50.4%) in the soluble and exchangeable fraction, calcium (39.7%) in the carbonates, oxides and reducible fraction, magnesium (59.2%) in the bound to organic matter, oxidisable and sulphidic fraction, and iron (54.6%) in the residual fraction. Correlations between all the variables have been studied and the results showed common sources to the metal fractions correlated in relation to the industrial activities and mainly the vehicular traffic.
A comparative evaluation of analytical green metrics for microextraction techniques based on polymeric and gel membranes as solid support
(Elsevier, 2024-07-05) Sedehi, Samira; Tabani, Hadi; Dorabadizare, Farzaneh; Pedersen-Bjergaard, Stig; Ramos Payán, María Dolores; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia e Innovación (MICIN). España
Sample preparation plays a pivotal role in chemical analysis, serving to isolate target analytes from diverse matrices and enhance measurement selectivity and sensitivity. This review examines microextraction's eco-friendliness versus tradition, focusing on LPME and EME systems for acidic compounds. Different solid supports (polymeric and gel membranes) implemented in different configurations are evaluated. These innovative techniques reduce the consumption of chemicals and offer enhanced environmental safety. To determine the greenness of these techniques, we employ three widely recognized metrics: Analytical Eco-Scale, Green Analytical Procedure Index (GAPI), and Analytical GREEnness (AGREE). Our comparative analysis provides insights into the strengths and weaknesses of these metrics and offers a holistic perspective on the greenness of microextraction techniques. This review contributes to the ongoing efforts in Green Analytical Chemistry by facilitating the selection of environmentally benign sample preparation methods, thus promoting sustainable laboratory practices, and minimizing adverse environmental impacts.
A comprehensive study of a new versatile microchip device based liquid phase microextraction for stopped-flow and double-flow conditions
(Elsevier, 2018-06) Ramos Payán, María Dolores; Santigosa Murillo, Elia; Coello, Jordi; Bello López, Miguel Ángel; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Educación y Ciencia (MEC). España
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 reusable.
A comprehensive study of a new versatile microchip device based liquid phase microextraction for stopped-flow and double-flow conditions
(Elservier, 2018-04-30) Ramos Payán, María Dolores; Santigosa-Murillo, Elia; Coello, Jordi; Bello López, Miguel Ángel; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Educación y Ciencia (MEC). España
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 reusable
A green microfluidic method based liquid phase microextraction for the determination of parabens in human urine samples
(Elsevier, 2022-06) Dowlatshah, Samira; Saraji, Mohammad; Ramos Payán, María Dolores; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia e Innovación (MICIN). España; Microliquid S.L.; Universidad de Sevilla. FQM291: Análisis Químico
Development of green approaches have emerged as a challenge that highlight the pressing need for nontoxic solvents, miniaturized method and bio-degradable materials. In this regard, an environmentally-friendly microfluidic system based on natural deep eutectic solvents (DESs) immobilized in agarose membranes was developed to extract parabens from urine samples for the first time. A comprehensive study of the support liquid membrane showed that only 3 µL of camphor and thymol (2:1 molar ratio) was an interesting option as a substitute for conventional (toxic) solvents used to date. Other experimental conditions were optimized and pH 4 (HCl) and 12 (NaOH) were selected as sample and acceptor solution, respectively. Both solutions (sample and acceptor) were fixed at 1 µL min⁻¹ as flow rate. The proposed green microfluidic device was successfully applied for the determination of parabens in urine samples with relative recoveries between 86 and 100% for all analytes. Detection limits and quantitation limits were between 0.011–0.093 and 0.31–0.38 µg mL⁻¹, respectively. Relative standard deviation was below 7% for all analytes. Furthermore, the environmentally-friendly solvent (Ca:Ty 2:1) used as SLM offered the same advantages in terms of membrane stability allowing consecutive extractions. Results were compared with experiments previously conducted using conventional (polypropylene) membranes, observing that highly green microextraction systems based on natural and biodegradable materials have proven to be an attractive alternative in microfluidic systems.
A green microfluidic method for the simultaneous extraction of polar and non-polar basic compounds in biological samples
(Elsevier, 2023-06) Martín, Alejandro; Santigosa, Elia; Ramos Payán, María Dolores; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España
Microfluidic devices as sample treatment have showed significant advancements in recent years, becoming an important tool in pharmaceutical analysis. In this work, a green microfluidic method for the simultaneous extraction of basic polar and non-polar compounds is proposed for the first time, offering a new and more sustainable and environmentally friendly alternative. A mixture of camphor:menthol 1:1 is presented as a new green supported liquid membrane (SLM) for the simultaneous extraction of a wide log P range for basic compounds (0.4 < log P < 5): verapamil hydrochloride (VRP), tyramine (TYR), atenolol (ATN), metopropol (MTP) and nortriptyline (NRP). Different SLMs were investigated to offer new other green alternatives for polar or non-polar basic drugs. Microfluidic operational parameters were also optimized at pH 1.5, pH 11.5 and 1 µL min−1 as acceptor phase, donor phase and donor flow rate, respectively. Camphor:menthol 1:1 showed good stability and reproducibility (RSD < 5%) in human urine samples. It was found to be an attractive alternative to traditional toxic organic solvents applied in microextraction techniques. The green microfluidic method offered good recoveries between 50 and 100% for all compounds in urine sample after 7 min extraction, using only 3 µL of Ca:Me 1:1 and showing a good long-term stability system up to 6 consecutive extraction in real samples. A relative standard deviation (n = 3) was below 6 % for all compounds with and without replacing the membrane of the system.
A microchip device based liquid-liquid-solid microextraction for the determination of permethrin and cypermethrin in water samples
(Elsevier, 2021-12) Dowlatshah, Samira; Ramos Payán, María Dolores; Saraji, Mohammad; Universidad de Sevilla. Departamento de Química Analítica
In this work, for the first time, a microchip device integrating liquid-liquid-solid phase microextraction is presented. As a novel approach to microchip systems, liquid-liquid-solid microextraction was performed in a sandwiched microchip device. The microchip device consisted of three poly(methyl methacrylate) layers along with a double “Y”-shaped microchannel. As the stationary phase, polyacrylonitrile-C18 was synthesized and immobilized in the upper channel, while the beneath channel was used as a reservoir for the stagnant volume ratio of sample-to-extraction solvent phase. In this way, analytes were extracted from an aqueous sample through an organic phase into the stationary phase. The analytes were finally desorbed with a minimum amount of acetonitrile as the desorption solvent. Permethrin and cypermethrin were selected as the model analytes for extraction and subsequent analysis by gas chromatography-flame ionization detection. Under optimum conditions (extraction solvent; n-hexane, sample -to-extraction solvent volume ratio; 2:1, extraction time; 20 min, desorption solvent; acetonitrile, desorption volume; 200 μL, and desorption time; 15 min) detection limits were 3.5 and 6.0 ng mL−1 for permethrin and cypermethrin, respectively. Relative standard deviations for intra- and inter-day reproducibility were below 8.3%. Device-to-device precision was in the range of 8.1–9.6%. The proposed microchip device was successfully applied to determine permethrin and cypermethrin in water samples with recoveries in the range of 73–96%.
A microfluidic liquid phase microextraction method for drugs and parabens monitoring in human urine
(Elsevier, 2021) Dowlatshah, Samira; Saraji, Mohammad; Fernández Torres, Rut; Ramos Payán, María Dolores; Universidad de Sevilla. Departamento de Química Analítica
Frequent consumption of pharmaceuticals and personal care products (PPCPs) have emerged as a current problem that highlights the pressing need for new multi-residue analytical methods that allow their simultaneous determination to assess their overall effect on human health. In this regard and for the first time, a versatile microfluidic based- liquid phase microextraction (LPME) method was developed for simultaneous monitoring of ten compounds from six different classes: amoxicillin, sulfadiazine, sulfamerazine, tiamphenicol, ethyl 4-hydroxybenzoate, flumequine, propyl 4-hydroxybenzoate, 5-hydroxydiclofenac, 3-hydroxydiclofenac and diclofenac. The microfluidic device was combined with a HPLC-UV system for the separation and determination of the model analytes in the sample. Optimal conditions were reached using 2-nitrophenyl octyl ether as supported liquid membrane, pH 3.5 as donor phase, pH 11.5 as acceptor phase, 0.5 µL min−1 as donor flow rate and 1 µL min−1 as acceptor flow rate. Under optimal method conditions, the extraction efficiency was between 85 and 100% for most compounds after 10 min extraction, and it was successfully applied in non-diluted human urine, with recoveries between 70 and 100% for all analytes except for sulfamerazine (52% recovery). In addition, the extraction of metabolites (3-hydroxydiclofenac and 5-hydroxydiclofenac) was also demonstrated in microfluidic systems with recoveries between 71 and 100% in human urine. The proposed method allowed consecutive extraction and only requires 5 µL of organic solvent and less than 15 µL of sample volume.
A multiple hollow fibre liquid-phase microextraction method for the determination of halogenated solvent residues in olive oil
(Springer Nature, 2014) Manso, J.; García Barrera, Tamara; Gómez Ariza, José Luis; González González, Antonio Gustavo; Universidad de Sevilla. Departamento de Química Analítica; Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España
The present paper describes a method based on the extraction of analytes by multiple hollow fibre liquid-phase microextraction and detection by ion-trap mass spectrometry and electron capture detectors after gas chromatographic separation. The limits of detection are in the range of 0.13-0.67 μg kg -1, five orders of magnitude lower than those reached with the European Commission Official method of analysis, with three orders of magnitude of linear range (from the quantification limits to 400 μg kg-1 for all the analytes) and recoveries in fortified olive oils in the range of 78-104 %. The main advantages of the analytical method are the absence of sample carryover (due to the disposable nature of the membranes), high enrichment factors in the range of 79-488, high throughput and low cost. The repeatability of the analytical method ranged from 8 to 15 % for all the analytes, showing a good performance.
A neuroimaging study of pleasant and unpleasant olfactory perceptions of virgin olive oil
(CSIC, 2016) Vivancos García, Jorge; Tena Pajuelo, Noelia; Morales Millán, María Teresa; Aparicio López, Ramón; García-González, Diego Luis; Universidad de Sevilla. Departamento de Química Analítica
Functional magnetic resonance imaging (fMRI) has been used to collect information from neurons that receive direct input from olfactory bulbs when subjects smell virgin olive oil. The pleasant aroma of three extra virgin olive oils (var. Royal, Arbequina and Picual) and three virgin olive oils with sensory defects (rancid, fusty and winey/vinegary) were presented to 14 subjects while a fMRI scan acquired data from the brain activity. Data were subjected to a two-sample t test analysis, which allows a better interpretation of results particularly when data are studied across different subjects. Most of the activations, which were located in the frontal lobe, are related to the olfactory task regardless of the hedonic component of perception (e.g. Brodmann areas 10, 11). Comparing the samples with pleasant and unpleasant aromas, differences were found at the anterior cingulate gyrus (Brodmann area 32), at the temporal lobe (Brodmann area 38), and inferior frontal gyrus (Brodmann area 47), while intense aromas activated Brodmann area 6. The actual perceptions described by the subjects and the concentration of the odorant compounds in the samples were considered in the interpretation of the results.
A New Microchip Design. A Versatile Combination of Electromembrane Extraction and Liquid-Phase Microextraction in a Single Chip Device
(American Chemical Society, 2018-08-09) Ramos Payán, María Dolores; Santigosa, Elia; Fernández Torres, Rut; Bello López, Miguel Ángel; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Educación y Ciencia (MEC). España
For thefirst time, a novel and versatile microfluidic device wasdeveloped to achieve the possibility of combining different extraction principlesusing a miniaturized approach for the extraction of different classes of analytes.This novel microchip is composed of a sandwich of three poly(methylmethacrylate) (PMMA) layers. Four channels allowed the combination ofelectromembrane extraction (EME) and liquid-phase microextraction (LPME) inthree different ways: (I) EME and LPME, (II) EME and EME, or (III) LPME andLPME. The microchip can be used either (a) using a common acceptor phase (forboth extractions) for the simultaneous extraction of drugs from different nature in asingle step, or (b) a common sample solution (for both extractions) and twoacceptor solutions for simultaneous drug separation. In this work, the performanceof this novel microchip was demonstrated by simultaneous integration of EME andLPME using a common acceptor phase for both extractions. This configurationreduces the time of analysis allowing direct analysis in a single chip. The microchip was tested for extracting two different classesof analytes:fivefluoroquinolones and four parabens as model analytes. All effective variables were optimized for EME andLPME. Under the optimized conditions, the reusable microchip enables simultaneousμ-EME/LPME with extractionefficiencies over 77% in only 8 min extraction and sample volume consumption lower than 40μL. The optimized procedure wassuccessfully applied to urine samples obtaining recoveries over 90% for all analytes.
A Novel Integrated Platform Enabling Simultaneous Microextraction and Chemical Analysis on-chip
(Elsevier, 2023) Santigosa Murillo, Elia; Moreno, Alexandre; Ramos Payán, María Dolores; Ríos, Juan Manuel; Muñoz Berbel, Xavier; Muñoz, María; Giménez Gómez, Pablo; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Agencia de Gesti´o d’Ajusts Universitaris i de Recerca
The 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.
A Potentiometric Evaluation of Stability Constants of Two-Step Overlapping Equilibria via a Bilogarithmic Hyperbolic Cosine Method
(Japan Society for Analytical Chemistry, 2016) Beaumont, Samuel; Martín Bueno, Julia; García Asuero, Agustín; Universidad de Sevilla. Departamento de Química Analítica
A bilogarithmic hyperbolic cosine method for the evaluation of overlapping formation constants at varying (or fixed) ionic strength is devised in this paper and applied to data reported in the analytical literature, i.e. succinic acid system, Cu(II)-glycine system and Ag(I)-aminobutan -1-ol system. The method is based on the linearization of the formation function ñ = f(pH) or ñ = f(pL) data. A theoretical slope of unity should be obtained thus proving the correctness of the assumed equilibria. An additional advantage of the bilogarithmic method proposed is that it provides a closed scale representation of Y and X unlike other plots. This paper forms part of an investigation into the uses of bilo garithmic methods and hyperbolic functions in parameter estimation. Methods based on the application of spectrophotometric measurements have been the subject of recent studies.
A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa
(ARC Journals, 2018) Díaz Montaña, Enrique Jacobo; Alcázar Rueda, Ángela; Jurado Jurado, José Marcos; Pablos Pons, Fernando de; Universidad de Sevilla. Departamento de Química Analítica; Universidad de Sevilla. AGR104: Proyecto Sexia
A practical example, focused on the evaluation of uncertainty and its propagation in spectrophotometric determination of ionization constants, is proposed in this work. The Hildebrand - Reilley method has been used in order to calculate the acetaminofen pKa value. After applying this method a linear relationship between pH and a logarithmic term depending on absorbances, was established. The value of pKa is obtained as the intercept of this straight-line and its error is evaluated from least squares calculations. As errors in both variables have to be considered, weighted least squares (WLS) must be used. The evaluation of uncertainty in pH measurements was carried out according to IUPAC recommendations in the case of glass electrode with two calibration standards. The uncertainty contributions of absorbance and work standard concentration, evaluated according to GUM, have been propagated to Hildebrand – Reilley expression in order to obtain the errors to be used in WLS calculations. Due to the different topics included in this tutorial, it can be considered as a useful tool for training people learning about the evaluation of uncertainty in measurements and its propagation.
A rapid and versatile microfluidic method for the simultaneous extraction of polar and non-polar basic pharmaceuticals from human urine
(Elsevier, 2022) Santigosa, Elia; Pedersen-Bjergaard, Stig; Giménez Gómez, Pablo; Muñoz, María; Ramos Payán, María Dolores; Universidad de Sevilla. Departamento de Química Analítica; Agencia de Gestió d'Ajusts Universitaris i the Recerca; Agencia Estatal de Investigación. España
In sample preparation, simultaneous extraction of analytes of very different polarity from biological matrixes represents a challenge. In this work, verapamil hydrochloride (VRP), amitriptyline (AMP), tyramine (TYR), atenolol (ATN), metopropol (MTP) and nortriptyline (NRP) were used as basic model analytes and simultaneously extracted from urine samples by liquid-phase microextraction (LPME) in a microfluidic device. The model analytes (target compounds) were pharmaceuticals with 0.4 < log P < 5. Different organic solvents and mixtures of them were investigated as supported liquid membrane (SLM), and a mixture of 2:1 (v/v) tributyl phosphate (TBP) and dihexyl ether (DHE) was found to be highly efficient for the simultaneous extraction of the non-polar and polar model analytes. TBP reduced the intrinsic hydrophobicity of the SLM and facilitated extraction of polar analytes, while DHE served to minimize trapping of non-polar analytes. Sample and acceptor phase composition were adjusted to pH 12 and pH 1.5, respectively. Urine samples were pumped into the microfluidic system at 1 μL min-1 and the extraction was completed in 7 min. Recoveries exceeded 78% for the target analytes, and the relative standard deviation (n = 4) was below 7% in all cases. Using five microliters of SLM, the microfluidic extraction system showed good long-term stability, and the same SLM was used for more than 18 consecutive extractions.
A rapid Soxhlet and mini-SPE method for analysis of polycyclic aromatic hydrocarbons in atmospheric particles
(Springer, 2021-02-16) Castro Guijarro, Pablo Antonio; Álvarez Vázquez, Eusebio Ramón; Fernández Espinosa, Antonio José; Universidad de Sevilla. Departamento de Química Analítica; Junta de Andalucía; Universidad de Sevilla. RNM294: Química Analítica Ambiental
An analytical method was validated with two reference materials of polycyclic aromatic hydrocarbons in atmospheric particles. Standard reference materials (SRMs) were incorporated into the matrix of unexposed cut quartz filters. The methodology was previously designed and extraction of polycyclic aromatic hydrocarbons (PAHs) from fortified filters was based on a rapid lowcost method, for a low consumption of volume and time. The optimisation combined a low-volume Soxhlet apparatus used in hot Soxhlet mode with a quick clean-up by solid-phase extraction with special cartridges. The quantification of target compounds was performed by gas chromatography/mass spectroscopy in SIMmode. Temperatures of injector and oven program of the GCMS were also optimised. Experimental variables of both systems were successfully optimised and validated, achieving a robust analytical methodology.
A selective and efficient microfluidic method-based liquid phase microextraction for the determination of sulfonamides in urine samples
(Elsevier, 2021) Dowlatshah, Samira; Santigosa, Elia; Saraji, Mohammad; Ramos Payán, María Dolores; Universidad de Sevilla. Departamento de Química Analítica
Liquid phase microextraction (LPME) into a microfluidic has undergone great advances focused on downscaled and miniaturized devices. In this work, a microfluidic device was developed for the extraction of sulfonamides in order to accelerate the mass transfer and passive diffusion of the analytes from the donor phase to the acceptor phase. The subsequent analysis was carried out by high performance liquid chromatography with UV-DAD (HPLC-DAD). Several parameters affecting the extraction efficiency of the method such as the supported liquid membrane, composition of donor and acceptor phase and flow rate were investigated and optimized. Tributyl phosphate was found to be a good supported liquid membrane which confers not only great affinity for analytes but also long-term stability, allowing more than 20 consecutive extractions without carry over effect. Under optimum conditions, extraction efficiencies were over 96 % for all sulfonamides after 10 minutes extraction and only 10 µL of sample was required. Relative standard deviation was between 3-5 % for all compounds. Method detection limits were 45, 57, 54 and 33 ng mL−1 for sulfadiazine (SDI), sulfamerazine (SMR), sulfamethazine (SMT) and sulfamethoxazole (SMX), respectively. Quantitation limits were 0.15, 0.19, 0.18 and 0.11 µg mL−1 for SDI, SMR, SMT SMX, respectively. The proposed microfluidic device was successfully applied for the determination of sulfonamides in urine samples with extraction efficiencies within the range of 86-106 %. The proposed method improves the procedures proposed to date for the determination of sulfonamides in terms of efficiency, reduction of the sample volume and extraction time.
A simple and fast Double-Flow microfluidic device based liquid-phase microextraction (DF-µLPME) for the determination of parabens in water samples
(Elsevier, 2017-04-01) Ramos Payán, María Dolores; Maspoch, Santiago; Llobera, Andreu; Universidad de Sevilla. Departamento de Química Analítica
A fast double-flow microfluidic based liquid phase microextraction (DF-µLPME) combined with a HPLC-UV procedure using diode array detection has been developed for the determination of the four most widely used parabens: Ethyl 4-hydroxybenzoate (EtP), Propyl 4-hydroxybenzoate (PrP), Butyl 4-hydroxybenzoate (BuP) and IsoButyl 4-hydroxybenzoate (iBuP) in water samples. Parabens have successfully been determined in environmental (lake and river water) samples with excellent clean up, high extraction efficiency and good enrichment factor using double-flow conditions. The microfluidic device consists of two micro-channels, which contain the acceptor and sample solution separated by a flat membrane (support liquid membrane). The sample (0.32 mM HCl) and acceptor phase (5.6 mM NaOH) are delivered to the µLPME at 10 µL min−1 and 1 µL min−1 flow rate, respectively. The extraction efficiencies are over 84% for all compounds in water samples with enrichment factors within the range of 9–11 and recoveries over 80%. The procedure provides very low detection limits between 1.6 and 3.5 µg L−1. The extraction time and the volume required for the extraction are 5 min and 50 µL, respectively; which are greatly lower compared to any previous extraction procedure for parabens analysis. In addition, this miniaturized DF- µLPME procedure significantly reduces costs compared to not only the existing methods for paraben detection, but also to the existing analytical techniques for sample preparation.
A study of the differences between trade standards inside and outside Europe
(Consejo Superior de Investigaciones Científicas (CSIC), 2017) García-González, Diego Luis; Tena Pajuelo, Noelia; Aparicio Ruiz, Ramón; Morales Millán, María Teresa; Romero del Río, Inmaculada; Aparicio López, Ramón; Universidad de Sevilla. Departamento de Química Analítica
The definitions of olive oil categories are common or very similar for all the international regulatory bodies, and in many cases the text is even literally the same. However, the values of some parameters which chemically define the different categories do not have the same degree of agreement. These disagreements mean a difficult task for importers and exporters who have to deal with these differences when they need to defend the quality and genuineness of their product. This work analyzes the differences found when scrutinizing the current trade standards and regulations from a critical viewpoint, with comments and useful tips for improving the current International Olive Council methods when possible, as well as alternatives from non targeted techniques. The values of precision associated with the International Olive Council methods are also examined and the need for re-validating methods to update the analytical quality parameters is discussed.
A study of the dynamic changes of stability taking place during virgin olive oil storage period examined by mesh cell-FTIR spectroscopy
(Elsevier, 2022) Lobo Prieto, Ana; Tena Pajuelo, Noelia; Aparicio Ruiz, Ramón; Morales Millán, María Teresa; García González, Diego L.; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia e Innovación (MICIN). España
Virgin olive oil (VOO) stability needs to be controlled to guarantee that the oil keeps the quality declared on the label during distribution. However, the stability is changing as storage progresses and its estimation under moderate conditions are difficult to accomplish, due to the challenge of implementing rapid stability evaluation under the environmental variables given in long storage periods. The main objective of this work was to study the dynamic changes of VOO stability taking place during storage. For this purpose, a realistic storage approach of 27 months was designed. The stability of the oils was evaluated at different months by incubating the oil on mesh cell and scanning FTIR spectra during this incubation (mesh cell-FTIR). Although the storage of the oils did not show remarkable spectral changes, the spectra from mesh cell incubation showed variations at different months, which evidenced a change in the stability as the oil aged. The results revealed that the stability changes were abrupt during VOO ageing. In general terms, the results showed that these changes mainly occurred during the first 6 months. The incubation in mesh cell-FTIR spectroscopy is able to detect the minor chemical changes occurring in VOO during storage under moderate conditions.

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