Persona: Monago Maraña, Olga
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Publicación Isocratic LC–DAD–FLD method for the determination of flavonoids in paprika samples by using a rapid resolution column and post-column pH change(Elsevier, 2016-05-15) Galeano Díaz , Teresa; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThe determination of flavonoid compounds in paprika samples has been performed by liquid chromatography in series diode array and fluorescence detection (LC–DAD–FLD), by means of a pH change to basic medium just before FLD detection. The validation of the method was performed through the establishment of the external standard calibration curves and the analytical figures of merit. Limits of detection ranging from 0.006 to 0.02 mg L−1 and 0.007 to 0.09 mg L−1 were achieved using DAD and FLD detection, respectively. The experimental conditions to carry out the hydrolysis procedure to obtain flavonoid aglycones from flavonoid glycosides have been optimized applying an experimental design and the response surface methodology. The final conditions selected were 2.5 M HCl during 45 min at 85 °C. The repeatability of this procedure was assayed and relative standard deviation (RSD) values for concentration of quercetin and luteolin compounds were lower than 2%. The quantification of quercetin, luteolin and kaempferol compounds was carried out in less than 6 min in paprika samples by means of the external standard calibration. The analytes were extracted with methanol and the extracts were previously subjected to a cleanup procedure to extend the use of the chromatographic column.Publicación Determination of Quercetin and Luteolin in Paprika Samples by Voltammetry and Partial Least Squares Calibration(Wiley, 2017-09-19) Chamizo González, Francisco; Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaQuercetin and luteolin are flavonoids with beneficious properties, which are present in paprika. In this work, both have been determined in paprika by using electrochemistry combined with chemometrics. The electrochemical oxidation mechanisms of both analytes have been studied through sampled direct current (DC) voltammetry, differential pulse voltammetry (DPV) and Square Wave Voltammetry (SWV), making use of a glassy carbon electrode. The final technique selected for the quantification was DPV due to its high repeatability with respect SWV. The chemical variables and the instrumental parameters were optimized and the final conditions employed were ethanol: water (20 : 80), 0.75 mol dm−3 of HCl, and a pulse amplitude of 50 mV. Due to the facts that oxidation potential of both analytes were quite similar, their DPV peaks were overlapped, and also because the analytes interaction during the electrochemical process causes a non-additivity of the signals, they could not be quantified separately by direct measurement of peak intensity. For this reason, a chemometric algorithm was applied (partial least squares (PLS) regression in its modality PLS-2). In the case of validation samples, appropriate sets of calibration and validation were built and good results were obtained. This methodology was applied to real paprika samples and the results were similar to those obtained with a HPLC method previously reported.Publicación Chemometric Discrimination Between Smoked and Non-Smoked Paprika Samples. Quantification of PAHs in Smoked Paprika by Fluorescence-U-PLS/RBL(Springer Nature, 2016-10-10) Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThis study presents a strategy for differentiating paprika obtained by means of different drying systems. The differentiation is performed using spectroscopic fluorescence in combination with multivariate analysis. The two groups of samples (smoked or non-smoked paprika) are classified according to the content of some of their fluorescent compounds presented in each group, among which several polycyclic aromatic hydrocarbons (PAHs) are included. These compounds are characteristic in smoked food. The full information of excitation–emission matrices (EEMs) is processed with the aid of unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis (LDA) and discriminant unfolded partial least squares (DU-PLS). The last algorithm allows an adequate classification of unknown paprika samples. Besides, the quantification of several PAHs in paprika was performed by means of unfolded partial least squares with residual bilinearization (U-PLS/RBL). On this way, three (fluorene, phenantrene, and anthracene) out of the five (fluorene, phenantrene, anthracene, pyrene and chrysene) selected analytes were quantified.Publicación Four- and five-way excitation-emission luminescence-based data acquisition and modeling for analytical applications. A review(Elsevier, 2019-11-20) Alcaraz, Mirta R.; Goicoechea, Héctor C.; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThe latest advances in both theory and experimental procedures on third-order/four-way and fourth-order/five-way calibration methods are discussed. This report is focused on excitation–emission (fluorescence and phosphorescence) matrices generation, employing different variables as the third data mode (time retention in chromatography, pH gradient, fluorescence/phosphorescence lifetime, kinetics, or other chemical treatments). Fully capitalizing on the second-order advantage, it has been possible to develop appealing analytical applications in spite of the complexity of the data. Extraction of the significant chemical information about the system under study as well as the individual abundance of the contributing constituents after proper higher-order data decomposition has allowed to analytical researchers performing quantitative analysis of complex samples. The experimental works reported up to the present are introduced and discussed in order to illustrate concepts. Throughout this work, the analytical benefits achieved by modeling third- and fourth-order data are exposed, attempting to contribute to the ongoing debate in the chemometric community regarding the existence and the true nature of the third-order advantage.Publicación Determination of pungency in spicy food by means of excitation-emission fluorescence coupled with second-order chemometric calibration(Elsevier, 2018-04) Guzmán Becerra, María; Muñoz de la Peña, Arsenio; Galeano Díaz, Teresa; Monago Maraña, OlgaCapsaicinoids are a family of compounds responsible for the pungency of spicy foods. In this work, the combination of fluorescence and chemometrics was investigated as a novel quantification method of capsaicinoids in spicy food samples. The excitation–emission matrices (EEMs) of the two major capsaicinoids (capsaicin and dihydrocapsaicin) were identical. Hence, the results were presented as the total content of capsaicinoids. The EEMs of a group of paprika, cayenne and chilli peppers, and of another group of spicy sauces were registered. The decomposition of the EEMs of each group was performed by parallel factor analysis (PARAFAC), obtaining three principal components in each case. After the decomposition, the component corresponding to capsaicinoids was identified by comparison with the profile of a standard mixture of capsaicin and dihydrocapsaicin. In addition, the score values of this component were correlated with the Scoville heat units (SHU) calculated by means of an HPLC–FLD method. Good correlations were obtained in both groups (0.998 and 0.992), confirming the assignation of the component to capsaicinoids. Subsequently, a calibration set was built to carry out the calibration in the spectrofluorimeter, using PARAFAC and U-PLS/RBL as second-order calibration algorithms. Good results for SHU determination were obtained in both groups with both algorithms and when the fluorimetric method was validated by means of liquid chromatographic analysis the relative error of prediction was less than 11.3%.Publicación Combination of Liquid Chromatography with Multivariate CurveResolution-Alternating Least-Squares (MCR-ALS) in the Quantitationof Polycyclic Aromatic Hydrocarbons Present in Paprika Samples(American Chemical Society, 2016-10-07) Pérez, Rocío L; Escandar, Graciela M.; Muñoz de la Peña, Arsenio; Galeano Díaz, Teresa; Monago Maraña, OlgaThis work presents a strategy for quantitating polycyclic aromatic hydrocarbons (PAHs) in smoked paprikasamples. For this, a liquid chromatographic method withfluorimetric detection (HPLC-FLD) was optimized. To resolve some interference co-eluting with the target analytes, the second-order multivariate curve resolution-alternating least-squares (MCR-ALS) algorithm has been employed combined with this liquid chromatographic method. Among the eight PAHs quantified(fluorene, phenanthrene, anthracene, pyrene, chrysene, benzo[a]anthracene, benzo[b]fluoranthene, and benzo[a]pyrene) byHPLC-FLD, only in the case offluorene, pyrene, and benzo[b]fluoranthene was it necessary to apply the second-order algorithmfor their resolution. Limits of detection and quantitation were between 0.015 and 0.45 mg/kg and between 0.15 and 1.5 mg/kg,respectively. Good recovery results (>80%) for paprika were obtained via the complete extraction procedure, consisting of anextraction from the matrix and the cleanup of the extract by means of silica cartridges. Higher concentrations of chrysene,benzo[a]anthracene, benzo[b]fluoranthene, and benzo[a]pyrene were found in the paprika samples, with respect to the maximalamounts allowed for other spices that are under European Regulation (EU) N°2015/1933Publicación Characterization of Spanish Paprika by Multivariate Analysis of Absorption and Fluorescence Spectra(Taylor and Francis Group, 2016-04-21) Bartolomé García, Teresa de Jesús; Galeano Díaz, Teresa; Kostrzewa Rutkowska, Z.; Monago Maraña, OlgaSpanish paprika was clustered on the basis of the Spanish Protected Designation of Origin “Pimentón de La Vera” by molecular absorbance and fluorescence with principal component analysis and parallel factor analysis. Rapid extraction of carotenoids, capsaicinoids, and tocopherols was optimized; the best conditions included ethanol as the extractant, an extraction time of 10 min in an ultrasonic bath, and a sample size of 0.1 g. The procedure provided good precision with a relative standard deviation of 1.2% for four samples. Molecular absorption spectra were obtained from 250 to 600 nm and fluorescence excitation and emission spectra were collected from 200 to 295 nm and 300 to 400 nm, respectively. Forty-eight “Pimentón de La Vera” paprika samples and 19 samples from other origins were characterized. A principal component analysis model was constructed from the absorption spectra and clustering was obtained based on the origin. Parallel factor analysis was performed on the fluorescence data and better characterization of the origin was obtained.Publicación Fluorescence properties of flavonoid compounds. Quantification in paprika samples using spectrofluorimetry coupled to second order chemometric tools(Elsevier, 2016-04-01) Durán Merás, Isabel; Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThe influence of pH on the fluorescence of flavonoid compounds was investigated and the highest fluorescence emission was obtained in basic medium. Selected conditions to improve this signal were: pH 9.5, 0.14 M Britton Robinson buffer and methanol between 5% and 10%. The excitation–emission fluorescence matrices of a set of 36 samples of Spanish paprika were analyzed by means of parallel factor analysis (PARAFAC). Thus, the profiles of possible fluorescence components (PARAFAC loadings) were obtained. One of these profiles was identified by matching PARAFAC scores with LC analysis on the same samples. Two clusters of samples were obtained when score values were plotted against each other. Spectrofluorimetry coupled to second order multivariate calibration methods, as unfolded-partial least squares with residual bilinearization (U-PLS/RBL) and multidimensional-partial least-squares with residual bilinearization (N-PLS/RBL), was investigated to quantify quercetin and kaempferol in those samples. Good results were obtained for quercetin by this approach.Publicación Non-destructive Raman spectroscopy as a tool for measuring ASTA color values and Sudan I content in paprika powder(Elsevier, 2019-02-15) Eskildsen, Carl Emil; Afseth, Nils Kristian; Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Wold, Jens Petter; Monago Maraña, OlgaThe aim of this study was developing a non-destructive method for the determination of color in paprika powder as well as for detecting possible adulteration with Sudan I. Non-destructive Raman spectroscopy was applied directly to paprika powder employing a laser excitation of 785 nm for the first time. The fluorescence background was estimated, by fitting a polynomial to each spectrum, and then subtracted. After preprocessing the spectra, some peaks were clearly identified as characteristic from pigments present in paprika. The preprocessed Raman spectra were correlated with the ASTA color values of paprika by partial least squares regression (PLSR). Twenty-five paprika samples were adulterated with Sudan I at different levels and the PLSR model was also obtained. The coefficients of determination (R2) were 0.945 and 0.982 for ASTA and Sudan I concentration, respectively, and the root mean square errors of prediction (RMSEP) were 8.8 ASTA values and 0.91 mg/g, respectively. Finally, different approaches were applied to discriminate between adulterated and non-adulterated samples. Best results were obtained for partial least squares – discriminant analysis (PLS-DA), allowing a good discrimination when the adulteration with Sudan I was higher than 0.5%.