Papers by Eladia Peña-méndez
Chemosphere, May 1, 2016
Silver nanoparticles (AgNP) are emerging pollutants. The use of novel materials such as Cu-(benze... more Silver nanoparticles (AgNP) are emerging pollutants. The use of novel materials such as Cu-(benzene 1,3,5-tricarboxylate, BTC) Metal-Organic Framework (MOFs), for AgNP adsorption and their removal from aqueous solutions has been studied. The effect of different parameters was followed and isotherm model was suggested. MOFs adsorbed fast and efficiently AgNP in the range C0 < 10 mg L(-1), being Freundlich isotherm (R = 0.993) these data fitted to. Among studied parameters a remarkable effect of chloride on sorption was found, thus their possible interactions were considered. The high adsorption efficiency of AgNP was achieved and it was found to be very fast. The feasibility of adsorption on Cu-(BTC) was proved in spiked waters. The results showed the potential interest of new material as adsorbent for removing AgNP from environment.
Journal of Capillary Electrophoresis, 1998
Capillary zone electrophoretic determination of iodide in seawater using transient isotachophores... more Capillary zone electrophoretic determination of iodide in seawater using transient isotachophoresis with artificial seawater as the background electrolyte We describe an application of capillary zone electrophoresis (CZE) with transient isotachophoresis (ITP) as the on-line concentration procedure for the determination of iodide in seawater. The effective mobility of iodide was decreased by the addition of 10 mM cetyltrimethylammonium chloride (CTAC) to an artificial seawater background electrolyte (BGE) so that transient ITP functioned and iodide was separated from other coexisting anions such as bromide, nitrite, and nitrate in seawater samples. After sample injection, 600 mM acetate was separately injected into the capillary as the terminating ion to generate transient ITP. The limit of detection (LOD) for iodide was 3.0 mg/L. The LOD was obtained at a signal-to-noise ratio (S/N) of 3. The values of the relative standard deviation (RSD) of peak area, peak height, and migration time for iodide were 2.9, 2.1, and 0.6%. The proposed method was applied to the determination of iodide in seawater collected around the Osaka Bay. The results obtained by use of the calibration graph were agreed with those obtained by the addition of the standard solutions for iodide.
Frontiers in Medicine, Apr 1, 2021
The high infectivity of SARS-CoV-2 makes it essential to develop a rapid and accurate diagnostic ... more The high infectivity of SARS-CoV-2 makes it essential to develop a rapid and accurate diagnostic test so that carriers can be isolated at an early stage. Viral RNA in nasopharyngeal samples by RT-PCR is currently considered the reference method although it is not recognized as a strong gold standard due to certain drawbacks. Here we develop a methodology combining the analysis of from human nasopharyngeal (NP) samples by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with the use of machine learning (ML). A total of 236 NP samples collected in two different viral transport media were analyzed with minimal sample preparation and the subsequent mass spectra data was used to build different ML models with two different techniques. The best model showed high performance in terms of accuracy, sensitivity and specificity, in all cases reaching values higher than 90%. Our results suggest that the analysis of NP samples by MALDI-TOF MS and ML is a simple, safe, fast and economic diagnostic test for COVID-19.
ACS Chemical Neuroscience, Dec 30, 2022
Pathological pain subtypes can be classified as either neuropathic pain, caused by a somatosensor... more Pathological pain subtypes can be classified as either neuropathic pain, caused by a somatosensory nervous system lesion or disease, or nociplastic pain, which develops without evidence of somatosensory system damage. Since there is no gold standard for the diagnosis of pathological pain subtypes, the proper classification of individual patients is currently an unmet challenge for clinicians. While the determination of specific biomarkers for each condition by current biochemical techniques is a complex task, the use of multimolecular techniques, such as matrix-assisted laser desorption/ionization time-offlight mass spectrometry (MALDI-TOF MS), combined with artificial intelligence allows specific fingerprints for pathological pain-subtypes to be obtained, which may be useful for diagnosis. We analyzed whether the information provided by the mass spectra of serum samples of four experimental models of neuropathic and nociplastic pain combined with their functional pain outcomes could enable pathological pain subtype classification by artificial neural networks. As a result, a simple and innovative clinical decision support method has been developed that combines MALDI-TOF MS serum spectra and pain evaluation with its subsequent data analysis by artificial neural networks and allows the identification and classification of pathological pain subtypes in experimental models with a high level of specificity.
European Food Research and Technology, May 1, 2004
The heavy metal composition of 80 samples of heat treated pork liver pastes from different brands... more The heavy metal composition of 80 samples of heat treated pork liver pastes from different brands canned in three different type of container was analysed. The metal concentration in the pastes together with multivariate techniques such as linear discriminant analysis, principal component analysis and factor analysis allow us to study the latent structure in the samples and follow the influence of the material of the container or/and the brand of origin.
Scientific Reports, Feb 25, 2021
Metal-doped gold clusters, mainly cages, are receiving rapidly increasing attention due to their ... more Metal-doped gold clusters, mainly cages, are receiving rapidly increasing attention due to their tunable catalytic properties. Their synthesis is mostly based on complex procedures, including several steps. In this work, via adsorption of gold nanoparticles (AuNPs) from aqueous solution to MOF (metal organic frameworks) of M = Co, Cu, Ni, and Zn with various linkers the {AuNPs, MOF} composites were prepared. These composites were used for laser ablation synthesis (LAS) using a common mass spectrometer. Several series of positively and negatively charged Au m M n +/− clusters were observed in mass spectra and their stoichiometry (m = 1-35, n = 1-5) was determined. For each dopant (Co, Cu, Ni, and Zn) ~ 50 different clusters were identified in positive, as well as in negative ion modes. About 100 of these clusters were proposed to be endohedral metal-doped gold cages (for m > 12). The developed approach represents a simple procedure for generating metal-doped gold clusters or endohedral metal-doped gold cages materials with potential applications in medicine and/or electronics. The discovery of doped gold clusters has increased attention to studying the catalytic effect of gold nanoparticles (AuNPs) due to their potential tunable properties 1-5. The introduction of a metal-dopant atom in the gold clusters changes their electronic, optical, and catalytic properties; thus, metal-doped gold clusters have become an important line of research 1,6-9. Based on the density functional theory (DFT) and photoelectron spectroscopy (PES), the formation of stable cage-like gold clusters with internal space near to that of fullerenes was evidenced 10. Internal space in gold cages enables the encapsulation of foreign metals 2,3. The first stable endohedral-doped gold cages were predicted using DFT and experimentally demonstrated using PES for the W@Au 12 and Mo@ Au 12 molecules based on the 18-electron rule 11. Subsequently, an investigation of M@Au 12 prompted extensive attention to designing novel endohedral-doped gold cages, namely those comprising 12, 14, 15, 16, 17, and 19 gold atoms, for example 1-3,6,12-15. The standard approach for clusters generation is based primarily on the laser vaporisation of metal targets (as precursors) in the presence of carrier gas (He); this process is referred to as laser ablation synthesis (LAS) 16-18. Recently, other precursors have been introduced e.g. metal organic frameworks (MOF) 19,20. MOF is a broad class of 3D-porous materials with a diverse chemical composition, tunable pore size, and high surface area 21. MOF can be a host for metal nanoparticles (i.e. AuNPs) to form {AuNPs, MOF} composites 22,23. AuNP-loaded MOF materials have various applications in catalysis, biomedical applications, and gas storage and separation 21,24. MOF composites with adsorbed AuNPs of different size, and/or shape, derivatisation or composition can be used for the LAS of metal-doped gold clusters, as demonstrated for the first time for iron 25. It was shown that the laser ablation of the {AuNPs, Fe-MOF} composite generates iron-doped gold clusters (containing up to 5 iron atoms). Some of these clusters were suggested to be endohedral iron-doped gold cages. Stabilisation of gold cages via encapsulation of foreign metal atom is well known, and it will be followed in this work 5,7,13,26. Tunable properties of AuNPs and different MOF compositions show many advantages compared to LAS from metal
Social Science Research Network, 2021
A new Cotton@Fe-BTC composite formed by Fe-BTC (BTC-H3 : trimesic acid) metal framework (Fe-BTC M... more A new Cotton@Fe-BTC composite formed by Fe-BTC (BTC-H3 : trimesic acid) metal framework (Fe-BTC MOF loading as high 38 wt %) supported by cellulose fibre is synthesised in aqueous media using a simple and green preparation method, described for the first time in this manuscript. This new strategy relies on the synergetic effect of the pure cellulose and MOFs frameworks resulting in hybrid nanofibers of MOFs@cellulose composite. A complete characterization of the composite material reveals its structural similarity to MIL-100(Fe), a Fe-BTC material. The Cotton@Fe-BTC composite potential use as an eco-friendly and low-cost adsorbent was evaluated for its adsorptive performance for the removal of dyes belonging to the triarylmethane dye family (Malachite Green (MQ), Brilliant Green (BG), Pararosaniline (PR), Basic Fuchsine (BF), Crystal Violet (CV), Methyl Green (Met-G), Victoria Blue B (VB), Acid Fuchsin (AF) and Aniline Blue (AB)) in aqueous solution. The fast kinetics and high dye removal efficiencies ( > 90%) obtained in aqueous solutions. The structure of Cotton@Fe-BTC netwok, contributed to the remarkable adsorption properties towards a variety of triphenylmethanedyes. The interparticle studies showed two main steps in the dye’s adsorption processes, with the exception of AF and BG. The equilibrium adsorption capacities qe (mg/g) follow the order: AF (3.64) < Met-G (3.70) < AB (4.87) < PR (5.52) < BF (5.76) < Met-G (7.22) < CV (9.63) < BG (16.34). However, going insight the adsorption mechanisms, it was remarkable the finding that the reaction paths taking into account the influence of water molecules on the anionic dye adsorption, through the so-called solvation/desolvation penalty processes, may not be ignored. The easy preparation and manipulation of Cotton@Fe-BTC network as well as its stability and excellent performance for the adsorption makes this material a good candidate for a broad range of applications.
Journal of Agricultural and Food Chemistry, 2010
Eight cultivars of different colored onions (white, golden, and red) were evaluated for fresh bul... more Eight cultivars of different colored onions (white, golden, and red) were evaluated for fresh bulbs cultivated and grown under the same environmental and agronomical conditions. Cluster analysis and principal component analysis, based on different flavonoids, total phenols, and pungency, data showed that the onions were not clustered according to variety (genetic similarity degree), whereas the color was the variable with the highest influence, ranging between 50 and 70%. Artificial neural networks were applied to study the possibility of discriminating among onion varieties. Characterization of the onion according to variety and procedence of the seeds was around 95-100%. Samples belonging to the Carrizal Alto procedence had an incorrect classification for 25% of the data.
Bioorganic Chemistry, Feb 1, 2021
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Environmental Nanotechnology, Monitoring and Management, Dec 1, 2021
Abstract The direct synthesis of nano-{Fe-BTC} MOFs was performed following green chemistry rules... more Abstract The direct synthesis of nano-{Fe-BTC} MOFs was performed following green chemistry rules. This nanomaterial has been characterized by several techniques showing structural similarities with commercial Fe-BTC MOFs, although it has greater porosity due to the presence of mesopores and micropores, that can make it an efficient adsorbent for fluorescent anionic dyes through electrostatic and π-π interactions between dye and nano-{Fe-BTC}. The adsorption isotherms fit the Freundlich model: tetrabromo-fluorescein(Br-FL) has the highest KF value, followed by dichloro-fluorescein(Cl-FL) and fluorescein(FL). The kinetic study suggests that the adsorption onto nano-{Fe-BTC} follows the pseudo-second-order model and the adsorption capacities follow the order Br-FL (qe 0.836 mg·g−1) > FL (qe 0.106 mg·g−1) ~Cl-FL (qe 0.100 mg·g−1), pH = 4. The use of methanol (5% NH3) allows recoveries of the dyes from nano-{Fe-BTC} ranging from 90% to100%. The presence of inorganic ions and organic substances in the water solution does not affect the adsorption of the dyes even when possible interfering species were present at concentrations that were up to 109 times higher than that of the dyes. The method was successfully applied to remove the target dyes from spiked water samples, showing the potential of high porous nano-{Fe-BTC} MOFs as a promising adsorbent for the effective removal of dyes from waters.
IntechOpen eBooks, Jun 2, 2021
Stem cells represent a unique cell type that is capable of self-renewal and differentiation into ... more Stem cells represent a unique cell type that is capable of self-renewal and differentiation into somatic cell types. Since the derivation of human embryonic stem cells and induced pluripotent stem cells, enormous potential has been recognized for disease modeling, drug development and regenerative medicine. Both embryonic stem cells and induced pluripotent stem cells possess the ability to differentiate into all three germ layers, hence they are naturally prone to respond to various differentiation stimuli. These inherent cellular fluctuations, which can result in risky phenotypic instability, must be addressed prior to introduction of these cells to human medicine, since they represent one of the major biosafety obstacles in the development of bio-industrial or clinical-grade stem cell cultures. Therefore, there is an ongoing need for novel robust, feasible and sensitive methods for determination and confirmation of the otherwise identical cells status, as well as for the detection of hidden divergences from their optimal state. A method of choice can be the intact cell mass spectrometry. Here we show how it can be applied in routine quality control of embryonic stem cell cultures.
Talanta, 2020
The magnetic metal-organic framework Fe 3 O 4 @(Fe-(benzene-1,3,5-tricarboxylic acid) (MMOF) was ... more The magnetic metal-organic framework Fe 3 O 4 @(Fe-(benzene-1,3,5-tricarboxylic acid) (MMOF) was prepared, characterized and studied as a magnetic sorbent for the dispersive solid-phase extraction (DSPE) of several widely used blood lipid regulators (i.e., bezafibrate, clofibric acid, clofibrate, gemfibrozil and fenofibrate) from water samples. Characterization of the synthesized Fe 3 O 4 @Fe-BTC magnetic nanomaterial was performed by Fourier transform infrared spectroscopy, powder X-ray diffractometry, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The magnetic nanocomposite was found to be chemically stable and to possess a large surface area (803.62 m 2 /g) and pore volume (0.59 cm³/g). The concentrations of fibrates in different water samples were determined using HPLC-UV-Vis and confirmed by UPLC-MS/MS. Parameters affecting the extraction efficiency of magnetic-DSPE were studied and optimized. The maxima absorption capacities (Q max) were determined to be (in mg/g) 197.0 for bezafibrate, 620.3 for clofibric acid, 537.6 for clofibrate, 288.7 gemfibrozil and 223.2 for fenofibrate. Validations of the optimized magnetic DSPE method for analyses at two fibrate concentrations in spiked water samples produced relative recovery values ≤ 70% for clofibrate and within the range of 80-100% for bezafibrate, clofibric acid, gemfibrozil and fenofibrate. LODs ranging from 4 μg/L for fenofibrate to 99 μg/L for gemfibrozil were obtained. The validated methodology produced recovery values ranging from 70 to 112% (relative standard deviations < 7%).
Heliyon, Dec 1, 2021
a Departamento de Química. Unidad Departamental de Química Analítica, Facultad de Ciencias, Unive... more a Departamento de Química. Unidad Departamental de Química Analítica, Facultad de Ciencias, Universidad de La Laguna, Tenerife, Spain. b Inorganic Chemistry Area, Section of Chemistry Faculty of Science; Instituto Universitario de BioOrgánica “Antonio González”, University of La Laguna, Tenerife, Spain. c Department de Química. Facultat de Ciències, Universitat de Girona, C/ Ma Aurèlia Capmany, 69, 17003 Girona, Spain d Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5/A14, 625 00 Brno, Czech Republic.
ABSTRACT Capillary zone electrophoresis (CZE) was used for the separation of humic acids. The inf... more ABSTRACT Capillary zone electrophoresis (CZE) was used for the separation of humic acids. The influence of the buffer solution on the separation of a commercial humic acid was studied. The use of an 8 mmol l−1 HCl-59.8 mmol l−1l-alanine buffer (pH 3.17) leads to the separation of humic acids into two fractions. The composition and pH of this buffer and some instrumental parameters such as voltage, injection volume and wavelength of detection were optimized and the quality parameters of the method were determined. Two further commercial humic acids were assayed. The one that showed the highest peak signal was used as a reference for the rough quantification of the others.
This contribution presents a comparative study of the use of PLS and ANNs to analyze A and C mixt... more This contribution presents a comparative study of the use of PLS and ANNs to analyze A and C mixtures using UV-Vis derivative spectra. The optimum ANN architecture enabling to model the system was established by means of TRAJAN 6.0 program. Several algorithms (Back propagation, Conjugate gradients, Quick propagation, and Delta-Bar Delta algorithm) were used for the training of the ANN to obtain a reliable model. With help of a suitable experimental design in combination with soft ANN modelling, the concentration of both A and C in mixtures can be quantified with an excellent accuracy (about 1 %). The quality of the testing set was evaluated on the basis of the average root mean square error for prediction (RMSEP) calculated from true and found values of A and C concentrations (RMSEP = 0.07 for A and 0.09 for C). It was found that ANN gives better results for the first and second derivative spectra than for original spectra. Furthermore, in comparison with PLS the ANN provides a more reliable and precise approach in the multicomponent analysis of A and C mixtures, where a number of different interactions take place.
The chemistry of gold nanoparticles (GNPs) represents fascinating interdisciplinary field of rese... more The chemistry of gold nanoparticles (GNPs) represents fascinating interdisciplinary field of research with applications in physics, chemistry, nanotechnology, and medicine, especially. GNPs are also used for the synthesis of novel nano-structured materials such as nanocomposites with graphene, carbon nano-tubes and/or fullerenes. Nanodiamonds (NDs) show unique mechanical, thermal and electrical properties which make them promising molecular building blocks in nanotechnology. Because of their biocompatibility and non-toxicity [1], NDs are used as drug carriers and building blocks e.g., for the fabrication of tissue scaffolds and surgical implants, etc. Metal carbides are extensively applied in industry. For a long time it was believed that gold is not forming carbides. Matthew in 1900 reported for the first time gold carbide (Au2C2) [2]. The formation of gold carbides via laser ablation synthesis was preliminarily indicated in our laboratory [3, 4]. Nowadays, it is known that i) gold forms not only carbides but also aurides and ii) gold-carbon interaction is important for development of electronic devices. The aim of this work is to study the formation of gold carbides via laser ablation synthesis (LAS) using as a precursor a kind of nanocomposite of GNPs with NDs. The GNPs-NDs nanocomposite (Fig. 1 a) was prepared and characterized by atomic force and transmission electron microscopy, energy dispersive X-ray spectroscopy and mass spectrometry. Laser ablation synthesis of gold carbides (Fig. 2) was carried out by laser desorption ionisation time-of-flight mass spectrometry (LDI-TOF-MS). Example of mass spectrum indicating the formation of singly charged AumCn+ clusters is given in Fig. 1 b. Gold carbides AuCn+ (n = 1-11), Au2Cn+ (n = 1-16) and Au3Cn+ (n = 1-10) and also some gold aurides were observed. The structure of observed AumCn clusters most probably corresponds to gold carbides, but also endohedral supramolecular complex formation, e.g., Au@C10 is not excluded (Fig. 3) [5]. Such possibility was supported by modelling via semi-empirical approach using the HYPERCHEMTM program (release 5.1, 1998) from Hyper-cube Inc. (Gainesville, FL, USA). The confirmation of diamond doped structure with gold atom would mean the first experimental evidence of gold-doped NDs. Concluding, laser ablation of GNPs-NDs nanocomposite leads to synthesis of Au-C clusters. Stoichiometry of altogether 37 gold carbides was established while also some gold aurides were formed probably from partially hydrogenated NDs. It is suggested that some “gold carbides” might be gold-modified diamonds or gold-diamond endohedral complexes. Results concerning the synthesis via laser ablation might initiate development of new Au-C materials with specific properties.
Using PCA and CA humic acids can be classified and differences in Antarctica samples from the oth... more Using PCA and CA humic acids can be classified and differences in Antarctica samples from the others can be seen.
Supramolecular chemistry deals with the study of organized molecular systems in which the molecul... more Supramolecular chemistry deals with the study of organized molecular systems in which the molecules or ions are held together by non-covalent interactions [1, 2, 3]. The reversibility of such interactions makes supramolecular “dynamic” systems. This is the key principle on which the design of new molecular machines is based. Examples are given in Fig. 1-2.Also, the labile interactions between particular molecules and drug molecule are the way to develop new drug carriers which is nowadays topic of a high importance in medicine. The formation of supramolecular complexes is usually assisted by carrying out their synthesis preparing sufficient amount of the products and examining them by nuclear magnetic resonance (NMR) or other classical analytical techniques. This can be tedious and laborious process and might require rather high quantity of the reagents. Matrix Assisted Laser Desorption Ionisation (MALDI) and/or Surface Assisted Laser Desorption Ionisation (SALDI) Time Of Flight (TOF) mass spectrometry are traditionally used in Proteomics and Bio-Analytics. We have applied MALDI and SALDI for the fast screening to find out the formation of supramolecular complexes and/or to search for drug carriers. For this purpose, mass spectrometric analysis was used in combination with combinatorial experiments mixing the reactants, either in aqueous or organic phase and the products were then examined. Reactions can also be done directly on a MS target. In some cases, experimental design (ED) was also used in order to reduce the number of combinatorial experiments. In this work several examples of supramolecular complex formation using as hosts cyclic ethers, cyclodextrines, cucurbit[n]urils etc., and as guests fullerenes, nanoparticles, or drugs like antivirals, cisplatin, etc., will be given and discussed. The advantage is that the experiments can be done using minimal amount of the chemicals (such as 10-5 moles or less) which is important for scarce or expensive substances and materials. The proposed application of MALDI and SALDI TOF mass spectrometry with ED represents an efficient and economic way to search for the formation of new supramolecular complexes and/or for possible drug carriers.
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Papers by Eladia Peña-méndez