DQFA-Artículos

URI permanente para esta colecciónhttps://hdl.handle.net/10953/276

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A green metal–organic framework to monitor water contaminants
(RSC Advance, 2018-09) Rocío-Bautista, Priscilla; Pino, Verónica; Pasán, Jorge; Ayala-Díaz, Juan; Ruiz-Pérez, Catalina; Afonso, Ana M.
The CIM-80 material (aluminum(III)-mesaconate) has been synthetized in high yield through a novel green procedure involving water and urea as co-reactants. The CIM-80 material exhibits good thermal stability with a working range from RT to 350 °C with a small contraction upon desolvation. Moreover, this material is stable in water at different pH values (1–10) for at least one week, and shows a LC50 value higher than 2 mg mL−1. The new material has been tested in a microextraction methodology for the monitoring of up to 22 water pollutants while presenting little environmental impact: only 20 mg of CIM-80 and 500 μL of acetonitrile are needed per analysis. The analytical performance of the CIM-80 in the microextraction strategy is similar to or even better for several pollutants than that of MIL-53(Al). The average extraction efficiencies range from ∼20% for heavy polycyclic aromatic hydrocarbons to ∼70–100% for the lighter ones. In the case of the emerging contaminants, the average extraction efficiency can reach values up to 70% for triclosan and carbamazepine.
A magnetic-based dispersive micro-solid-phase extraction method using the metal-organic framework HKUST-1 and ultra-high-performance liquid chromatography with fluorescence detection for determining polycyclic aromatic hydrocarbons in waters and fruit tea infusions
(Elsevier, 2016-03) Rocío-Bautista, Priscilla; Pino, Verónica; Ayala-Díaz, Juan; Pasán, Jorge; Ruiz-Pérez, Catalina; Afonso, Ana M.
A hybrid material composed by the metal-organic framework (MOF) HKUST-1 and Fe3O4 magnetic nanoparticles (MNPs) has been synthetized in a quite simple manner, characterized, and used in a magnetic-assisted dispersive micro-solid-phase extraction (M-d-μSPE) method in combination with ultra-high-performance liquid chromatography (UHPLC) and fluorescence detection (FD). The application was devoted to the determination of 8 heavy polycyclic aromatic hydrocarbons (PAHs) in different aqueous samples, specifically tap water, wastewaters, and fruit tea infusion samples. The overall M-d-μSPE-UHPLC-FD method was optimized and validated. The method is characterized by: its simplicity in both the preparation of the hybrid material (simple mixing) and the magnetic-assisted approach (∼10 min extraction time), the use of low sorbent amounts (20 mg of HKUST-1 and 5 mg of Fe3O4 MNPs), and the low organic solvent consumption in the overall M-d-μSPE-UHPLC-FD method (1.5 mL of acetonitrile in the M-d-μSPE method and 2.8 mL of acetonitrile in the UHPLC-FD run). The resulting method has high sensitivity, with LODs down to 0.8 ng L−1; adequate intermediate precision, with relative standard deviation values (RSD) always lower than 6.3% (being the range 5.9–9.0% in tap water for a spiked level of 45 ng L−1, 6.1–14% in wastewaters for a spiked level of 45 ng L−1, and 7.2–17% in fruit tea infusion samples for a spiked level of 45 ng L−1); and adequate relative recoveries, with average values of 82% in tap water, and 94% and 75% in wastewater and fruit tea infusion samples, respectively, if using the proper matrix-matched calibration.
Ambient (desorption/ionization) mass spectrometry methods for pesticide testing in food: a review
Beneito-Cambra, Miriam; Gilbert-López, Bienvenida; Moreno-González, David; Bouza, Marcos; Franzke, Joachim; García-Reyes, Juan F.; Molina-Díaz, Antonio
Ambient mass spectrometry refers to the family of techniques that allows ions to be generated from condensed phase samples under ambient conditions and then, collected and analysed by mass spectrometry. One of their key advantages relies on their ability to allow the analysis of samples with minimal to no sample workup. This feature maps well to the requirements of food safety testing, in particular, those related to the fast determination of pesticide residues in foods. This review discusses the application of different ambient ionization methods for the qualitative and (semi)quantitative determination of pesticides in foods, with the focus on different specific methods used and their ionization mechanisms. More popular techniques used are those commercially available including desorption electrospray ionization (DESI-MS), direct analysis on real time (DART-MS), paper spray (PSMS) and low-temperature plasma (LTP-MS). Several applications described with ambient MS have reported limits of quantitation approaching those of reference methods, typically based on LC-MS and generic sample extraction procedures. Some of them have been combined with portable mass spectrometers thus allowing “in situ” analysis. In addition, these techniques have the ability to map surfaces (ambient MS imaging) to unravel the distribution of agrochemicals on crops.
Ambient (desorption/ionization) mass spectrometry methods for pesticide testing in food: a review
(Royal Chemical Society, 2020-08-02) Beneito-Cambra, Miriam; Gilbert-López, Bienvenida; Moreno-González, David; Bouza, Marcos; Franzke, Joachim; García-Reyes, J. Francisco; Molina-Díaz, Antonio
Ambient mass spectrometry refers to the family of techniques that allows ions to be generated from condensed phase samples under ambient conditions and then, collected and analysed by mass spectrometry. One of their key advantages relies on their ability to allow the analysis of samples with minimal to no sample workup. This feature maps well to the requirements of food safety testing, in particular, those related to the fast determination of pesticide residues in foods. This review discusses the application of different ambient ionization methods for the qualitative and (semi)quantitative determination of pesticides in foods, with the focus on different specific methods used and their ionization mechanisms. More popular techniques used are those commercially available including desorption electrospray ionization (DESI-MS), direct analysis on real time (DART-MS), paper spray (PS-MS) and low-temperature plasma (LTP-MS). Several applications described with ambient MS have reported limits of quantitation approaching those of reference methods, typically based on LC-MS and generic sample extraction procedures. Some of them have been combined with portable mass spectrometers thus allowing “in situ” analysis. In addition, these techniques have the ability to map surfaces (ambient MS imaging) to unravel the distribution of agrochemicals on crops.
Ambient Diode Laser Desorption Dielectric Barrier Discharge Ionization Mass Spectrometry of Nonvolatile Chemicals
(ACS Publications, 2013-02-19) Gilbert-López, Bienvenida; Schilling, Michael; Alhmann, Norman; Michels, Antje; Hayen, Heiko; Molina-Díaz, Antonio; García-Reyes, Juan Francisco; Franzke, Joachim
In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface.
Analytical pyrolysis (Py-GC-MS) for the assessment of olive mill pomace composting efficiency and the effects of compost thermal treatment
(Elsevier, 2022) Peña-Rueda, Marta; Comino-Romero, Francisco; Aranda-Sanjuán, Víctor; Domínguez-Vidal, Ana; Ayora-Cañada, María José
Composting is an interesting solution for recycling the large amount of residues typically generated in olive oil production areas, particularly olive mill pomace. Bulking agents must be added to wet olive mill pomace for composting. The diversity of the materials used (such as olive tree-pruning residues, animal manure, or straw) and the variable proportion, in which they are mixed, are responsible for the heterogeneity and variability of the quality of the produced compost. For this reason, a comprehensive characterization of compost organic matter is necessary to gain information about its stability and maturity useful as well as to predict its behavior as a soil amendment. In this work, fresh olive mill pomace and four composted olive mill pomace samples were characterized using analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS). Results showed a large variety of pyrolysis products, many of which had a specific biochemical origin. Pyrolysis-GC-MS revealed a decrease in fatty acids and aliphatic compounds content with composting, along with carbohydrates degradation and an increase in phenolic and N-compounds levels. Furthermore, the differences observed in organic matter characteristics had an impact on agronomic aspects (water repellency and phytotoxicity). Thus, the occurrence of fatty acids in incompletely composted materials (mainly palmitic and cis-vaccenic acids) was associated with increased phytotoxicity and higher water repellency. The presence of chicken manure in the mixtures was proved to favor the humification process and the production of stabilized compost (characterized by a lower Aliphatic-C/Aromatic-C ratio and higher N-heterocycles content). Furthermore, in this work, the effectiveness of applying thermal treatments to improve compost quality has been evaluated. Analysis of the Py-GC-MS results by means of principal component analysis (PCA) revealed thermal rearrangement, predominantly aromatization, and loss of functional groups of carbohydrates, lignin, and proteins, at temperatures above 225 ºC. Interestingly, the results suggest that materials with a non-effective or incomplete composting process can be transformed by thermal treatment into more stable products, exhibiting similar agronomic characteristics as those have that undergone a more efficient biotransformation.
Chemical profiling, antioxidant, enzyme inhibitory and molecular modelling studies on the leaves and stem bark extracts of three African medicinal plants
(Elsevier, 2019-05-22) Sadeer, Nabeelah Bibi; Llorent-Martínez, Eulogio José; Bene, Kouadio; Mahomoodally, Mohamad Fawzi; Mollica, Adriano; Sinan, Kouadio Ibrahime; Stefanucci, Azzurra; Ruiz-Riaguas, Alba; Fernández-de Córdova, María Luisa; Zengin, Gokhan
Africa is famous for its floral biodiversity, exploited by local people for therapeutic purposes. However, such plants need to be scrutinised scientifically for the presence of bioactive compounds and possible biological properties. This study attempts for the first time to highlight the pharmacological and phytochemical profile of extracts prepared from leaves and stem barks of three African plants (Macaranga hurifolia Beille, Sterculia tragacantha Lindl. and Zanthoxylum gilletii (De Wild.) P. G. Waterman. The extracts were tested for antioxidant and enzyme inhibitory effects. Free radical scavenging, metal chelator, reducing power and phosphomolybdenum assays were performed to evaluate antioxidant effects. To identify enzyme inhibitory effects, cholinesterases (acetylcholinesterase (AChE) and butrylcholinesterase (BChE)), tyrosinase, alpha-amylase and alpha-glucosidase were selected as target enzymes. High performance liquid chromatography-Electrospray tandem mass spectrometry (HPLC-ESI-MS) technique was also used for chemical profiling. ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assays showed that the stem barks of all three African plants were better scavenger than leaf extracts. Sterculia tragacantha was found to be a better metal chelator (64.10 ± 4.66 mg EDTAE/g) among the studied plants. All extracts exhibited good clinical enzyme inhibitory activities. The stem bark of S. tragacantha exhibited the best acetylcholinesterase activity compared to the other plants. HPLC-ESI-MS characterization showed that the most abundant compounds in stem bark were flavonoids in M. hurifolia (4.2 ± 0.2 mg/g DE), proanthocyanidins in S.tragacantha (42 ± 1 mg/g DE) and similar concentrations of phenolic acids and flavonoids in Z. gilletii (2.8–3.1 mg/g DE). Based on the biological activity, the most abundant and relevant bioactive compounds in the extracts were studied using molecular modelling approach against tyrosinase. The studied African plants showed good antioxidant and enzymatic propensities and thus can be considered as potential bioresources for future development of nutraceuticals and/or for pharmaceutical applications.
Comparative study of the phytochemical and mineral composition of fresh and cooked broccolini
(Elsevier, 2019-11-21) Llorent-Martínez, E.J.; Ortega-Vidal, J.; Ruiz-Riaguas, A.; Ortega-Barrales, P.; Fernández-de Córdova, M.L.
Broccolini is originated from crossing the regular broccoli with Chinese kale. Consequently, it has similar properties to these vegetables, but other very particular characteristics. Its consumption has increased in the last few years and, consequently, there have been some studies related to its quality parameters and the influence of different cooking methods. Nevertheless, changes on its phenolic composition and mineral content originated by its cooking have not been investigated in-depth so far. Here we report the phytochemical profile of broccolini before and after boiling, steaming, and griddling cooking treatments. The mineral content and phytochemicals were assessed by inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography-mass spectrometry (HPLC-MS), respectively. The main phenolics (mainly hydroxycinnamic acid derivatives from caffeic, coumaric, ferulic and sinapic acids) were quantified. Three oxylipins, three flavonoid glycosides and the glucosinolate glucobrassicin were also identified. ABTS and DPPH assays were also used as screening methods to assess the antioxidant potential of broccolini. A significant loss of the phenolic compounds and a reduction of the antioxidant activity were observed after the three cooking methods. Clear disadvantages were detected when broccolini was boiled, namely high losses of phenolic acids and derivatives (70%). Steaming and griddling also led to a significant loss of phenolics (50%) from fresh broccolini. The mineral content of this vegetable after domestic cooking procedures is also reported for the first time, calculating the contribution of broccolini consumption to official daily recommendations.
Comparing mapping and direct hyperspectral imaging in stand-off Raman spectroscopy for remote material identification
(Wiley, 2019) Gasser, Christoph; González-Cabrera, María; Ayora-Cañada, María José; Domínguez-Vidal, Ana; Lendl, Bernhard
Stand-off Raman spectroscopy offers a highly selective technique to probe unknown substances from a safe distance. Often, it is necessary to scan large areas of interest. This can be done by pointwise imaging (PI), that is, spectra are sequentially acquired from an array of points over the region of interest (point-by-point mapping). Alternatively, in this paper a direct hyperspectral Raman imager is presented, where a defocused laser beam illuminates a wide area of the sample and the Raman scattered light is collected from the whole field of view (FOV) at once as a spectral snapshot filtered by a liquid crystal tunable filter to select a specific Raman shift. Both techniques are compared in terms of achievable FOV, spectral resolution, signal-to-noise performance, and time consumption during a measurement at stand-off distance of 15 m. The HSRI showed superior spectral resolution and signal-to-noise ratio, while more than doubling the FOV of the PI at laser power densities reduced by a factor of 277 at the target. Further, the output hyperspectral image data cube can be processed with state of the art chemometric algorithms like vertex component analysis in order to get a simple deterministic false color image showing the chemical composition of the target. This is shown for an artificial polymer sample, measured at a distance of 15 m.
Comprehensive and heart-cutting multidimensional liquid chromatography–mass spectrometry and its applications in food analysis
(Wiley, 2023-04-13) Caño-Carrillo, Irene; Gilbert-López, Bienvenida; Montero, Lidia; Martínez-Piernas, Ana B.; García-Reyes, Juan F.; Molina-Díaz, Antonio
In food analysis, conventional one‐dimensional liquid chromatography methods sometimes lack sufficient separation power due to the complexity and heterogeneity of the analyzed matrices. Therefore, the use of two‐dimensional liquid chromatography (2D‐LC) turns out to be a powerful tool to consider, especially when coupled to mass spectrometry (MS). This review presents the most remarkable 2D‐LC–MS food applications reported in the last 10 years, including a critical discussion of the multiple approaches, modulation strategies as well as the importance of the optimization of the different analytical aspects that will condition the 2D‐LC–MS performance. The presence of contaminants in food (food safety), the food quality, and authenticity or the relationship between the beneficial effects of food and human health are some of the fields in which most of the 2D‐LC–MS applications are mainly focused. Both heart‐cutting and comprehensive applications are described and discussed in this review, highlighting the potential of 2D‐LC–MS for the analysis of such complex samples.
Conformational Flexibility of Limonene Oxide Studied By Microwave Spectroscopy
(Wiley, 2017) Loru, Donatella; Quesada-Moreno, María Mar; Avilés-Moreno, Juan Ramón; Jarman, Natasha; Huet, Thérèse R.; López-González, Juan Jesús; Sanz, María Eugenia
Monoterpenoids are biogenic volatile organic compounds (BVOCs) that play a major role in atmospheric chemistry, participating in the formation of aerosols. In this work, the monoterpenoid R-(+)-limonene oxide (C10H16O) has been characterized in the gas phase by Fourier transform microwave spectroscopy in a supersonic jet. Five conformers of limonene oxide, four equatorial and one axial considering the configuration of the isopropenyl group, have been unambiguously identified from the analysis of the rotational spectrum. The observed conformers include cis and trans forms, and are stabilised by a subtle balance of hydrogen bonds, dispersive interactions and steric effects. Estimated conformational relative abundances surprisingly reveal that the axial conformer has an abundance similar to some equatorial conformers. In addition, the potential energy surface was extensively explored using density functional theory and ab initio methods.
Conformational preference and chiroptical response of Carbohydrates D-Ribose and 2-Deoxy-D-ribose in aqueous and solid phases
(American Chemical Society, 2013) Quesada-Moreno, María del Mar; Azofra, Luis Miguel; Avilés-Moreno, Juan Ramón; Alkorta, Ibon; Elguero, José; López-González, Juan Jesús
This work targets the structural preferences of D-ribose and 2-deoxy-D-ribose in water solution and solid phase. A theoretical DFT (B3LYP and M06-2X) and MP2 study has been undertaken considering the five possible configurations (open-chain, α-furanose, β-furanose, α-pyranose, and β-pyranose) of these two carbohydrates with a comparison of the solvent treatment using only a continuum solvation model (PCM) and the PCM plus one explicit water molecule. In addition, experimental vibrational studies using both nonchiroptical (IR-Raman) and chiroptical (VCD) techniques have been carried out. The theoretical and experimental results show that α-and β-pyranose forms are the dominant configurations for both compounds. Moreover, it has been found that 2-deoxy-D-ribose presents a non-negligible percentage of open-chain forms in aqueous solution, while in solid phase this configuration is absent.
Determination of carbamates in edible vegetable oils by ultra-high performance liquid chromatography-tandem mass spectrometry using a new clean-up based on zirconia for QuEChERS methodology
(Elsevier, 2014-10) Moreno-González, David; Huertas-Pérez, José F.; García-Campaña, Ana M.; Gámiz-Gracia, Laura
In this study a fast, selective and sensitive multiresidue method based on QuEChERS methodology has been evaluated and validated for the determination of carbamate pesticides, in edible vegetable oils by UHPLC–MS/MS. A new clean-up sorbent, SupelTM QuE Z-Sep+, has been successfully applied in vegetable oil extracts. Z-Sep+ was compared with other sorbents (i.e. mixture of C18 and PSA) previously used for dispersive solid phase extraction of these matrices, reducing more effectively matrix effects without a significant decrease of analyte recoveries. Matrix effect was studied in different matrices (extra-virgin olive, sunflower, maize, linseed and sesame oil) being ≤│30│% for most of the studied pesticides. Under optimum conditions, recoveries ranged from 74% to 101%, with relative standard deviations lower than 10%. Limits of quantification ranged from 0.09 to 2.0 µg kg−1, allowing their determination at the low concentration levels demanding by current legislation.
Direct analysis of olive oil and other vegetable oils by mass spectrometry: a review
Beneito-Cambra, Miriam; Moreno-González, David; García-Reyes, Juan F.; Bouza, Marcos; Bienvenida Gilbert-López, Bienvenida; Molina Díaz, Antonio
Virgin olive oil (VOO) is a highly valued vegetable oil often subjected to fraud practices such as adulteration with lower prized oils such as seed oils and refined olive oil. Thus, there is a need to provide rapid tools that allow high-throughput authentication and quality control of VOO as well as other valued oils. Mass spectrometry offers unique features -such as specificity, sensitivity and speed of analysis-that map well against this challenge, either those based on atmospheric pressure ionization methods (ESI and APCI) or those occurring under vacuum conditions such as MALDI for nonvolatile species or headspace sampling-mass spectrometry using electron impact ionization (HS-MS) or chemical ionization (proton transfer reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS)) for volatile fraction analysis. In addition, more recent atmospheric pressure methods (Ambient MS) enable direct analysis with minor or even no sample manipulation. The aim of this article is to provide a critical overview on all these methods and their potential use for vegetable oil characterization, highlighting the strengths and weaknesses of the different
Dispersive liquid-liquid microextraction using a low density extraction solvent for the determination of 17 N-methylcarbamates by micellar electrokinetic chromatography-electrospray-mass spectrometry employing a volatile surfactant.
(Elsevier, 2012-07) Moreno-González, David; Gámiz-Gracia, Laura; Bosque-Sendra, Juan M; García-Campaña, Ana M.
A new analytical method based on micellar electrokinetic chromatography tandem mass spectrometry (MEKC–ESI–MS/MS) employing a MS friendly surfactant (ammonium perfluorooctanoate) is proposed and validated for the identification and simultaneous quantification of 17 N-methylcarbamate pesticides in environmental and drinking water samples. MS/MS detection using an ion trap as analyzer operating in the multiple reaction monitoring mode was used. Different parameters were optimized in order to obtain an adequate CE separation combined with the highest sensitivity in MS/MS. Dispersive liquid–liquid microextraction (DLLME) using a low-density extraction solvent has been proposed for extraction, obtaining a preconcentration factor of 10. Under optimum conditions, recoveries for fortified samples ranged from 83% to 101%, with relative standard deviations lower than 8%. The limits of detection ranged from 1 to 144 ng l−1, demonstrating the sensitivity and applicability of this fast, simple, and environmentally friendly method.
Evaluation of hydrophilic interaction liquid chromatography–tandem mass spectrometry and extraction with molecularly imprinted polymers for determination of aminoglycosides in milk and milk-based functional foods
(Elsevier, 2017-08-15) Moreno-González, David; Hamed, Ahmed M.; García-Campaña, Ana M.; Gámiz-Gracia, Laura
An analytical method for the determination of eleven aminoglycosides in different types of milk and milk-based functional products has been optimized and validated. A hydrophilic interaction chromatography (HILIC) column was proposed for the separation of analytes by ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). A commercially molecularly imprinted polymer has been used for the solid phase extraction of the analytes, in order to achieve high selectivity in the sample treatment. The proposed method was characterized for different types of milk (whole cow milk, skimmed cow milk, whole goat milk) and functional dairy products, such as follow-on milk, Omega 3-enriched milk and isoflavones-enriched milk. Matrix effect was studied in the different matrices, being lower than │15│% in all cases, showing that the proposed procedure provided very clean extracts. Limits of quantification in the range 4.2–49 µg kg−1 were estimated, well below the maximum residue limits established by the European Union. Recoveries ranged from 70% to 106% with RSD lower than 13%, in compliance with the current legislation. The combination of HILIC to solve the difficulties of the separation of these very polar compounds in reverse phase with the use of MISPE for sample treatment and MS/MS detection provided a very sensitive, highly selective, robust and useful method for identification and quantification of aminoglycoside residues in different types of milk and milk-based products.
Evaluation of processing factors for selected organic contaminants during virgin olive oil production: Distribution of BTEXS during olives processing
(Elsevier, 2016-05-15) López-Blanco, Rafael; Gilbert-López, Bienvenida; Rojas-Jiménez, Rubén; Robles-Molina, José; Ramos-Martos, Natividad; García-Reyes, Juan Francisco; Molina-Díaz, Antonio
The presence of BTEXS (benzene, toluene, ethylbenzene, xylenes and styrene) in virgin olive oils can be attributed to environmental contamination, but also to biological processes during oil lipogenesis (styrene). In this work, the processing factor of BTEXS from olives to olive oil during its production was evaluated at lab-scale with an Abencor system. Benzene showed the lowest processing factor (15%), whereas toluene and xylenes showed an intermediate behavior (with 40–60% efficiency), and ethylbenzene and styrene were completely transferred (100%). In addition, an attempt to examine the contribution of potential sources to olives contamination with BTEXS was carried out for the first time. Two types of olives samples were classified according to their proximity to the contamination source (road). Although higher levels of BTEXS were found in samples close to roads, the concentrations were relatively low and do not constitute a major contribution to BTEXS usually detected in olive oil.
Excited state intramolecular proton transfer (ESIPT) in 2-(2´-hydroxyphenyl)pyrimidines: synthesis, optical properties, and theoretical studies
(ACS Publications, 2022-05-17) Plaza-Pedroche, Rodrigo; Fernández-Liencres, M. Paz; Jiménez-Pulido, Sonia B.; Illán-Cabeza, Nuria A.; Achelle, Sylvain; Navarro, Amparo; Rodríguez-López, Julián
The development of fluorescence materials with switched on/of f emission has attracted great attention owing to the potential application of these materials in chemical sensing. In this work, the photophysical properties of a series of original 2-(2′-hydroxyphenyl)pyrimidines were thoroughly studied. The compounds were prepared by following well-established and straightforward methodologies and showed very little or null photoluminescence both in solution and in the solid state. This absence of emission can be explained by a fast proton transfer from the OH group to the nitrogen atoms of the pyrimidine ring to yield an excited tautomer that deactivates through a nonradiative pathway. The key role of the OH group in the emission quenching was demonstrated by the preparation of 2′-unsubstituted derivatives, all of which exhibited violet or blue luminescence. Single crystals of some compounds suitable for an X-ray diffraction analysis could be obtained, which permitted us to investigate inter- and intramolecular interactions and molecular packing structures. The protonation of the pyrimidine ring by an addition of trifluoroacetic acid inhibited the excited-state intramolecular proton transfer (ESIPT) process, causing a reversible switch on fluorescence response detectable by the naked eye. This acidochromic behavior allows 2-(2′-hydroxyphenyl)pyrimidines to be used as solid-state acid−base vapor sensors and anticounterfeiting agents. Extensive density functional theory and its time-dependent counterpart calculations at the M06-2X/6-31+G** level of theory were performed to rationalize all the experimental results and understand the impact of protonation on the different optical transitions.
Experimental and theoretical determination of pesticide processing factors to model their behavior during virgin olive oil production
(Elsevier, 2018-01-15) Lopez-Blanco, Rafael; Moreno-González, David; Nortes-Méndez, Rocío; García-Reyes, Juan Francisco; Molina-Díaz, Antonio; Gilbert-López, Bienvenida
The purpose of the present work was the experimental evaluation of pesticides transfer to virgin olive oil during the production step and prediction of their processing factors, which could be eventually used for the calculation of maximum residue limits (MRLs) in olive oil from the MRLs set in olives. A laboratory- scale Abencor system was used for the production of olive oil from olives spiked with the 104 pesticides studied, three different chromatographic methods being used for the analysis of raw olives and the obtained olive oil: (i) gas chromatography-tandem mass spectrometry (GC–MS/MS) for GC-amenable pesticides; (ii) hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/ MS) for polar pesticides, and; (iii) reversed-phase liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for low to medium polarity pesticides. Processing factors experimentally calculated were correlated to their octanol-water partitioning coefficient (log Kow), enabling the calculation of the equivalent MRLs in olive oil from the MRLs in olives, considering the percentage of oil extracted (oil yield) and the log Kow of each pesticide.
Fully Compatible and Ultra-Sensitive Micellar Electrokinetic Chromatography-Tandem Mass Spectrometry Using Sheathless Porous-Tip Interfacing
(Elsevier, 2017-11-17) Moreno-González, David; Haselberg, Rob; Gámiz-Gracia, Laura; García-Campaña, Ana M.; de Jong, Gerhardus J.; Somsen, Govert W.
The on-line coupling of micellar electrokinetic chromatography and mass spectrometry (MEKC-MS) is often hampered by incompatibility problems leading to reduced separation performance and unfavorable limits of detection (LODs). Here we propose a new selective and highly sensitive MEKC-MS/MS method employing a sheathless porous-tip interface in combination with a micellar phase comprised of semi-volatile surfactant molecules. Carbamate pesticides (CRBs) were selected as representative model compounds being neutral toxic pollutants potentially present at trace levels in environmental water samples. A background electrolyte of 75 mM perfluorooctanoic acid adjusted to pH 9.0 with ammonium hydroxide allowed efficient separation of 15 CRBs and appeared fully compatible with electrospray ionization (ESI)-MS. Interfacing parameters, such as the distance between the capillary tip and mass-spectrometer inlet, ESI voltage, and dry gas temperature and flow were optimized in order to attain good spray stability and high analyte signal-to-noise ratios. For CRBs the LODs ranged from 0.2 to 3.9 ng L−1 (13 nL injected, i.e., 2% of capillary volume), representing an improvement for certain CRBs of more than 300-fold when compared with conventional sheath-liquid interfacing. Good linearity (R2 > 0.99) and satisfactory reproducibility were obtained for all CRBs with interday RSD values for peak area and migration time of 4.0–11.3% and below 1.5%, respectively. Analysis of spiked mineral water showed that the new MEKC-MS/MS method allows selective and quantitative determination of CRB concentrations below the maximum residue limit of 100 ng L−1 without the need for sample preconcentration.

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