Examinando por Autor "Sierra, Isabel"

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2-Mercaptopyrimidine-functionalized mesostructured silicas to develop electrochemical sensors for a rapid control of scopolamine in tea and herbal tea infusions
(Elsevier, 2020) Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
Mesostructured silicas were synthesized and chemically functionalized with a 2- mercaptopyrimidine (MPY)-derivative. Bare and functionalized silicas (MSU-2, HMS, SBA-15, MSU-2-MPY, HMS-MPY and SBA-15-MPY) were characterized by powder X-ray diffraction, nitrogen adsorption-desorption isotherms, transmission electron and scanning electron microscopy, 29Si and 13C cross-polarization magic-angle spinning NMR spectroscopy and elemental analysis, and used to prepare modified carbon paste electrodes (CPEs). The electrodes properties were studied using potassium ferrocyanide and scopolamine as probes employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Results proved that MPY groups on the silica surface were necessary to improve the sensitivity in the voltammetric determination of scopolamine. CPE modified with HMS-MPY exhibited higher peak current toward the oxidation of scopolamine, with a well-defined oxidation peak at + 1.1 V (vs. Ag/AgCl) in DPV. This fact can be attributed to the high electroactive area of this material, with 3 D wormholelike channel structure that favored the scopolamine diffusion. Under optimum conditions, HMS-MPY-CPE exhibited a wider linearity range, from 0.9 to 200 μM, with a detection limit of 0.3 μM and good reproducibility by DPV. The developed sensor was successfully applied for a rapid determination of scopolamine in spiked tea and herbal tea infusion samples with good recoveries (between 83 ± 5 and 101 ± 1%).
A comparative study of phenolic composition and antioxidant activity in commercial and experimental seedless table grapes cultivated in a Mediterranean climate
(Springer, 2021-01) Izcara, Sergio; Morante-Zarcero, Sonia; Andrés, María Teresa de; Arroyo, Teresa; Sierra, Isabel
Grapes are important sources of phenolic compounds, which have multiple beneficial effects on human health. Scientific advances in the field of genetics have allowed the production of seedless table grape varieties, which are highly demanded by consumers because of their nutritional value and their easy consumption. In this study, total phenolic content (TPC), radical scavenging activity (RSA) and total anthocyanin content (TAC), were determined in 65 seedless table grape varieties (41 experimental and 24 commercial varieties). Ultra-high performance liquid chromatography coupled to an ion-trap mass spectrometry detector (UHPLC-IT-MS/MS) was used to identify and quantify some phenolic acids, flavan-3-ols, flavonols and stilbenes in 14 experimental varieties. TPC ranged from 17 to 250 mg gallic acid equivalents/100 g fresh weight (FW), RSA ranged from 15 to 269 mg Trolox equivalents/100 g FW and TAC ranged from 0 to 168 mg cyanidin-3-glucoside/100 g FW. The RSA assay showed high correlation (R2 = 0.90) between the TPC and the antioxidant activity of the 65 seedless table grapes analyzed. In the vast majority of the new experimental varieties analyzed, the TPC and TAC were similar to those of some common table grapes with seeds, indicating promising perspectives for their commercialization as potential sources of these bioactive compounds. In 6 grape varieties, high concentrations of catechin, procyanidin B2, epicatechin, quercetin 3-β-D-glucoside, 4-hydroxybenzoic acid, vanillic acid, caftaric acid and rutin were found, which would indicate that the regular intake of these varieties would be highly recommended.
A disposable electrochemical sensor based on bifunctional periodic mesoporous organosilica for the determination of lead in drinking waters
(Springer Verlag, 2015-07) Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
A new bifunctional disulfide- and tetrasulfide-bridged periodic mesoporous organosilica (PMO) with mercaptothiazoline ligand was synthesized and employed to prepare chemically modified carbon paste electrodes for Pb(II) detection in aqueous media by square wave adsorptive stripping voltammetry. To demonstrate the real interest of bifunctionalization, carbon paste electrodes were prepared with disulfide- and tetrasulfide-bridged PMO without mercaptothiazoline ligand. Results showed the importance of bifunctionalization of PMOs to improve the sensitivity for the determination of Pb(II) in water samples. To achieve the most accurate and sensitive Pb(II) measurements, optimization of the operating parameters in preconcentration and detection steps was performed. Finally, the modified carbon paste electrode prepared with bifunctional disulfide-bridged PMO with mercaptothiazoline ligand was applied to determine Pb(II) in different water samples without any pre-treatment. Using this electrode, the optimal operating conditions were 120 s of electrolysis time in HCl 0.4 M. In these conditions, the voltammetric signal increased linearly with the preconcentration time from 1 to 10 min. Under optimized conditions, the linear range was 2 - 100 ¿g/L (R2 = 0.9943) with a detection limit of 0.5 ¿g/L (for 5 min preconcentration time). Good reproducibility was achieved on both single and equally prepared electrodes. The accuracy of the method was validated by analysing Pb(II) in different drinking and natural water samples, with spiked recoveries in the range of 95 ¿ 105 ± 10%. The results demonstrated that the prepared electrochemical sensor exhibited selectivity, fast response time and exceptional long-time stability.
A Miniaturized QuEChERS Method Combined with Ultrahigh Liquid Chromatography Coupled to Tandem Mass Spectrometry for the Analysis of Pyrrolizidine Alkaloids in Oregano Samples
(MDPI, 2020) Izcara, Sergio; Casado, Natalia; Morante-Zarcero, Sonia; Sierra, Isabel
Recent and unexpected food alerts about relatively high amounts of pyrrolizidine alkaloids in oregano samples have stressed the need to develop analytical strategies to ensure food safety in this type of foodstu . Accordingly, this work presents the development of a miniaturized strategy based on the QuEChERS (quick, easy, cheap, e ective, rugged and safe) method combined with ultrahigh liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) for the determination of 21 pyrrolizidine alkaloids suggested by the European Food Safety Authority to be monitored in food. The analytical method was properly validated, with overall average recoveries from 77 to 96% and relative standard deviations <13% (n = 9). The method proved to be a sustainable analytical strategy which meets green analytical chemistry principles as it showed good performance by using small amounts of sample (0.2 g), organic solvents (1000 L), clean-up sorbents (175 mg) and partitioning salts (0.65 g). Its feasibility was verified through the analysis of 23 oregano samples. Of the samples analyzed, 100% were contaminated, with an average concentration of 1254 g/kg. Lasiocarpine, lasiocarpine N-oxide, europine, europine N-oxide, senecivernine, senecionine, echimidine N-oxide, lycopsamine N-oxide and intermedine N-oxide were the alkaloids which significantly contributed to the contamination of the samples.
A novel hybrid mesostructured silica for the solid-phase extraction of estrogenic hormones from waters
(Royal Society of Chemistry, 2015-04) Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
Mesoporous silica functionalized with octadecyl groups (denoted as SBA-15-C18) was prepared and characterized. The adsorption capacity of the prepared SBA-15-C18 for a mixture of twelve endocrine disrupting compounds (synthetic and natural estrogenic hormones) in aqueous media was evaluated by off-line solid-phase extraction (SPE) and compared with a commercial phase for SPE (ExtraBondR C18). Analytes were determined by high performance liquid chromatography with UV-Vis detection. Under optimized conditions (100 mg of SBA-15-C18 sorbent; conditioning: 2 mL methanol and 2 mL Milli-Q water; loading: 150 mL water sample; washing: 5 mL Milli-Q water; elution: 2 mL methanol; flow rate 0.5 mL min-1) the preconcentration factor achieved was 103. The analytical characteristics of this methodology were evaluated, showing good precision, accuracy and linerarity, with method quantification limits (MQL) between 0.16 and 3-00 ¿g L-1. The SBA-15-C18 material enabled the extraction of the twelve estrogenic hormones in tap water (pH 6.6), mineral water (pH 5.0), ground water (pH 7.3), river water (pH 5.0) and effluent wastewater (pH 5.0) with recoveries between 71 and 112% at the lower level studied (MQL).
A simple and sensitive portable system for a rapid evaluation of bisphenol A contamination in potable and environmental waters using a mesoporous silica-modified carbon paste electrode
(Taylor & Francis, 2019-04-29) Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Gañán, Judith; Sierra, Isabel
In this work, two ordered mesoporous silicas (HMS and SBA-15) were prepared and incorporated into carbon paste electrodes (CPEs) to obtain mesostructured sensors for a rapid determination of bisphenol A (BPA) in waters by voltammetric techniques. The materials were characterised by nitrogen adsorption-desorption measurements, transmission electron microscopy and scanning electron microscopy. The electrochemical properties of the modified carbon paste electrodes were studied by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Results showed that the sensor modified with HMS (HMS-CPE) exhibited strong adsorption activity toward the oxidation of BPA, with a welldefined voltammetric peak at +0.6 V. Moreover, the HMS-CPE exhibited a wider linearity range, from 0.44 to 3.5 μM BPA, with a detection limit of 61 nM (S/N = 3) and good reproducibility by DPV. The enhanced performance of the HMS-CPE could be attributed to its high surface area, with a 3 D wormhole-like channel structure that favoured an excellent accessibility, high adsorption capacity and faster adsorption rate of BPA. This novel sensor was coupled to a portable system and successfully applied for a rapid determination of BPA in tap, mineral, well and river water samples with good recovery, ranging from 98 ± 12 to 103 ± 7%.
Advances in Greener and Sustainable Sample Preparation for Tropane Alkaloid Analysis in Foods
(Springer, 2025-02-07) González-Gómez, Lorena; Fernández-Pintor, Begoña; Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
In the current context, Green Analytical Chemistry (GAC) focuses on promoting analytical methods that are more efficient and environmentally friendly. One of the fundamental principles of GAC is to reduce or eliminate the use of hazardous substances and minimize waste generation. One of the ways to achieve this is through the adoption of direct analytical techniques that can omit the sample preparation step. However, in the case of the determination of natural toxins, such as tropane alkaloids (TAs), carrying out direct analysis can be difficult due to several factors. For example, these compounds are often present in foods of plant origin with very complex matrices, in low concentrations, which makes their direct detection and quantification difficult. Therefore, in this context, sample preparation remains essential to clean up extracts and to concentrate analytes prior to their analysis. This chapter highlights the crucial importance of sample preparation in the determination of TAs. It emphasizes the fundamental role of miniaturized techniques and new materials applied in such techniques, which can contribute significantly to the search for more sustainable analytical practices. In this sense, an evaluation is carried out using the AGREEprep metric to analyze the miniaturized methods already published. This metric allows for a systematic evaluation of sample preparation methods in terms of their efficiency, sustainability, and compliance with the principles of Green Sample Preparation (GSP), which arises to better the principles of GAC. Positive and negative points of existing methods are identified, and possible modifications are suggested to improve their performance and make sample preparation greener.
Alicia Alonso. El Lago de los Cisnes. MD_AA_S_24 / 270
(1990-10-28) Sierra, Isabel; Instituto Universitario de Danza Alicia Alonso
Alicia Alonso. Giselle. MD_AA_S_33 / 447
(1931) Sierra, Isabel; Instituto Universitario de Danza Alicia Alonso
Alicia Alonso. Giselle. MD_AA_S_33 / 448
(1931) Sierra, Isabel; Instituto Universitario de Danza Alicia Alonso
Alicia Alonso. Giselle. MD_AA_S_57 / 712
(1931) Sierra, Isabel; Instituto Universitario de Danza Alicia Alonso
Alicia Alonso. Poema del amor y del mar. MD_AA_(N-Z)_S_372/3004
(1931) Sierra, Isabel; Instituto Universitario de Danza Alicia Alonso
Alicia Alonso. Poema del amor y del mar. MD_AA_(N-Z)_S_372/3005
(1931) Sierra, Isabel; Instituto Universitario de Danza Alicia Alonso
An improved and miniaturized analytical strategy based on μ-QuEChERS for isolation of polyphenols. A powerful approach for quality control of baby foods
(Elsevier, 2018-02-22) Casado, Natalia; Perestrelo, Rosa; L. Silva, Catarina; Sierra, Isabel; S. Câmara, José
An improved and miniaturized quick, easy, cheap, effective, rugged and safe (μ-QuEChERS) strategy combined with ultra-high pressure liquid chromatography coupled to a photodiode array detection system (UHPLC-PDA) was developed and optimized for the determination of twelve polyphenols in different baby foods samples. The proposed analytical approach proved to be highly cost-effective and environmentally friendly, since it showed good extraction efficiency using few amounts of sample (0.3 g), organic solvents (1000 μL), clean-up sorbents (87.5 mg) and partitioning salts (0.2 g), producing minimal waste disposal and reducing analysis time. Method performance was validated in terms of selectivity, linearity, limits of detection and quantification, matrix effects, precision and accuracy using different baby food matrices according to their composition. The overall average recoveries ranged from 71 to 100% with relative standard deviations lower than 6% (n = 18). The method was successfully applied to commercial baby food samples (including pureed solids, juices and porridges), and their total phenolic content (TPC) and antioxidant capacity (RSA) were also investigated. Results allowed characterizing the abundance of the selected polyphenols in the samples, and the highest RSA and TPC were found in the fruit-based baby foods. Thus, this work represents a first approach to determine the nutritional quality of these products.
Analytical Strategies for Green Extraction, Characterization, and Bioactive Evaluation of Polyphenols, Tocopherols, Carotenoids, and Fatty Acids in Agri-Food Bio-Residues
(MDPI, 2025-03-15) Vicente-Zurdo, David; Gómez-Mejía, Esther; Morante-Zarcero, Sonia; Rosales-Conrado, Noelia; Sierra, Isabel
Recent advancements in analytical strategies have enabled the efficient extraction and characterization of bioactive compounds from agri-food bio-residues, emphasizing green chemistry and circular economy principles. This review highlights the valorization of several agri-food bio-residues for the extraction of high-value-added bioactive compounds, particularly polyphenols, tocopherols, carotenoids, and fatty acids, as a biorefinery approach. To this end, the adoption of environmentally friendly extraction technologies is essential to improve performance, reduce energy consumption, and minimize costs. This study therefore examines emerging methodologies such as supercritical fluid extraction, pressurized liquid extraction, pulsed electric fields, and matrix solid-phase dispersion, highlighting their advantages and limitations. Additionally, the chemical characterization of these bioactive compounds is explored through spectrophotometric and high-resolution chromatographic techniques, crucial for their accurate identification and quantification. This is complemented by an analysis of bioactivity assays evaluating antioxidant, antimicrobial, anticancer, neuroprotective, and anti-inflammatory properties, with a focus on their applications in the food, pharmaceutical, and cosmetic industries. However, the analytical control of toxic compounds, such as alkaloids, in these bio-residues is undoubtedly needed. Ultimately, this approach not only promotes sustainability but also contributes to the development of eco-friendly solutions in various industries
Application of a hybrid large pore mesoporous silica functionalized with β-cyclodextrin as sorbent in dispersive solid-phase extraction. Toward sustainable sample preparation protocols to determine polyphenolic compounds in Arbutus unedo L. fruits by UHPLC-IT-MS/MS
(Elsevier, 2023-01) Izcara, Sergio; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
A quick, sensitive and selective analytical reversed-phase method using ultra-high performance liquid chromatography coupled to an ion-trap mass spectrometry detector (UHPLC-IT-MS/MS) was employed for the simultaneous determination of nine phenolic compounds (PCs) in strawberry tree (SBT) berries. The sample treatment included a solid-liquid extraction followed by a dispersive solid-phase extraction (dSPE) procedure using a hybrid large pore mesoporous silica (LP-MS) functionalized with β-cyclodextrin (β-CD) as sorbent material. For this purpose, the initial synthesized LP-MS was modified with β-CD following three different synthetic routes, obtaining three new functionalized materials (denoted LP-MS-β-CD-R1, LP-MS-β-CD-R2 and LP-MS-β-CD-R3). All synthesized materials were comprehensively characterized, showing excellent textural properties, and they were also tested as sorbent materials in the extraction of PCs by comparison of SPE and dSPE procedures. The LP-MS- β-CD-R2 as sorbent material in the dSPE procedure showed the best potential to extract and purify the target PCs, being more effective than the other materials and compared with the SPE procedure. The performance of the proposed dSPE-UHPLC-IT-MS/MS method was validated in terms of selectivity, linearity, LOD, LOQ, trueness, precision, and matrix effect, achieving good analytical method performance and demonstrating its feasibility and practicality for the quantification of PCs in SBT fruits. The analysis of the investigated SBT berries revealed, mainly, high contents of arbutin reaching concentrations up to 5979 μg/g dry weight, followed by catechin (661 μg/g dry weight). Arbutin was, undoubtedly, the major PC determined in all SBT berry samples analyzed, being the most prominent and showing a high concentration compared to that of other polyphenols determined in other red berries.
Application of a hybrid ordered mesoporous silica as sorbent for solid-phase multi-residue extraction of veterinary drugs in meat by ultra-high-performance liquid chromatography coupled to ion-trap tandem mass spectrometry
(Elsevier, 2016-06) Casado, Natalia; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
A quick, sensitive and selective analytical reversed-phase multi-residue method using ultra-high performance liquid chromatography coupled to an ion-trap mass spectrometry detector (UHPLC-IT-MS/MS) operating in both positive and negative ion mode was developed for the simultaneous determination of 23 veterinary drug residues (ß-blockers, ß-agonists and Non-Steroidal Anti-inflammatory Drugs (NSAIDs)) in meat samples. The sample treatment involved a liquid-solid extraction followed by a solid-phase extraction (SPE) procedure. SBA-15 type mesoporous silica was synthetized and modified with octadecylsilane, and the resulting hybrid material (denoted as SBA-15-C18) was applied and evaluated as SPE sorbent in the purification of samples. The materials were comprehensively characterized, and they showed a high surface area, high pore volume and a homogeneous distribution of the pores. Chromatographic conditions and extraction procedure were optimized, and the method was validated according to the Commission Decision 2002/657/EC. The method detection limits (MDLs) and the method quantification limits (MQLs) were determined for all the analytes in meat samples and found to range between 0.01-18.75 ¿g/Kg and 0.02-62.50 ¿g/Kg, respectively. Recoveries for 15 of the target analytes ranged from 71-98%. In addition, for comparative purpose SBA-15-C18 was evaluated towards commercial C18 amorphous silica. Results revealed that SBA-15-C18 was clearly more successful in the multi-residue extraction of the 23 mentioned analytes with higher recovery values. The method was successfully tested to analyze prepacked preparations of mince bovine meat. Traces of propranolol, ketoprofen and diclofenac were detected in some samples.
Application of the QuEChERS Strategy as a Useful Sample Preparation Tool for the Multiresidue Determination of Pyrrolizidine Alkaloids in Food and Feed Samples: A Critical Overview
(MDPI, 2022) Casado, Natalia; Morante-Zarcero, Sonia; Sierra, Isabel
The identification of concerning high levels of pyrrolizidine alkaloids (PAs) in a wide variety of food products has raised the occurrence of these natural toxins as one of the main current issues of the food safety field. Consequently, a regulation with maximum concentration levels of these alkaloids has recently been published to monitor their occurrence in several foodstuffs. According to legislation, the analytical methodologies developed for their determination must include multiresidue extractions with high selectivity and sensitivity, as a set of 21 + 14 PAs should be simultaneously monitored. However, the multiresidue extraction of these alkaloids is a difficult task due to the high complexity of food and feed samples. Accordingly, although solid-phase extraction is still the technique most widely used for sample preparation, the QuEChERS method can be a suitable alternative for the simultaneous determination of multiple analytes, providing green extraction and clean-up of samples in a quick and cost-effective way. Hence, this review proposes an overview about the QuEChERS concept and its evolution through different modifications that have broadened its applicability over time, focusing mainly on its application regarding the determination of PAs in food and feed, including the revision of published works within the last 11 years.
Atropine and scopolamine occurrence in spices and fennel infusions
(Elsevier, 2022-12-03) González-Gómez, Lorena; Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel
Tropane alkaloids (TAs) are toxic anticholinergic compounds that appear due to accidental contamination of foods with TA-producing plants. Atropine and scopolamine are the most common TAs and their maximum levels in certain foodstuffs have been recently regulated, including food supplements. TAs occurrence in commercial products and the transfer ratio to herbal infusions prepared from contaminated spices are of interest for exposure assessment of consumers. In this study, the occurrence of atropine and scopolamine was investigated in a total of 51 commercial spices of 6 types (ginger, cloves, fennel, cumin, aniseed, coriander) and a mix of spices and herbs (curry) purchased in Portugal (19 samples) and Spain (32 samples) in 2021. Results evidenced that more than half of the samples analysed (67%) were contaminated with one or both analytes. Fennel, cloves and coriander showed the highest concentrations ranging between 5-31 μg/kg, 8–28 μg/kg and 5–45 μg/kg, respectively, for the sum of atropine and scopolamine. On the other hand, the transfer ratio of the target analytes found in four naturally contaminated fennel samples was studied. Infusions were prepared according to International Standard ISO 3103 protocol, and a transfer ratio between 64 and 88% for atropine and between 47 and 57% for scopolamine was found.
Bi-functionalized mesostructured silicas as reversed-phase/strong anion-exchange sorbents. Application to extraction of polyphenols prior to their quantitation by UHPLC with ion-trap mass spectrometry detection
(SpringerLink, 2019-02-06) Casado, Natalia; Pérez-Quintanilla, Damián; Morante-Zarcero, Sonia; Sierra, Isabel
Hybrid mesostructured silicas with wormhole-like pore structure were synthesized and bi-functionalized with n-octyl (C8) and quaternary ammonium (NR4+) groups to obtain new sorbent materials for dispersive solid-phase extraction (dSPE) of polyphenols. Due to their nature of being both a reversed-phase and a strong anion-exchanger, the materials display mixed mode retention mechanism. During the synthesis, the functionalization conditions were varied to obtain materials with different functionalization degree. The resulting materials (denoted as HMS-RPC8-SAX-1, HMS-RPC8-SAX-2 and HMS-RPC8-SAX-3) show high surface area, wormhole-like framework and controlled pore size. They were evaluated for multicomponent extraction of 22 polyphenols, including phenolic acids, flavonoids and stilbenes, from spiked juice samples. The sample extracts were analyzed by ultra-high performance liquid chromatography coupled to ion-trap tandem mass spectrometry. The adsorption capability, the amount of sorbent, the eluent and the elution volume were optimized. Best performance was achieved by using HMS-RPC8-SAX-2, which is the material with the highest fraction of NR4+ groups. This material has a large extraction capability and provides high recovery values of the target analytes (70–101%) as a result of its hydrophobic and anion-exchange interactions. The detection limits for polyphenols in juice range from 1 to 560 ng mL−1.