On the signal contribution function with respect to different norms

The signal contribution function (SCF) in multivariate curve resolution evaluates signal portions of specific components either in absolute or in relative form related to the integrated signal of all components. In 1999, Gemperline used the summed signal data, and in 2001, Tauler worked with the square-summed relative signal in order to determine the profiles that minimize, respectively maximize, the signal contribution. These profiles approximate the bands of all feasible profiles. Here, Gemperline's approach using the entrywise 1-matrix norm is proved to provide accurate bounds for two-component systems. This revives the approach of summed mass or absorption values with its potentially better chemical interpretability.Fil: Neymeyr, Klaus. Universität Rostock; Alemania. Leibniz-Institut für Katalyse; AlemaniaFil: Sawall, Mathias. Universität Rostock; AlemaniaFil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica; Argentin

Residual bilinearization combined with kernel-unfolded partial least-squares: A new technique for processing non-linear second-order data achieving the second-order advantage

A new second-order multivariate calibration model is presented which allows one to process matrix data showing a non-linear relationship between signal and concentration, and achieving the important second-order advantage. The latter property permits analyte quantitation even in the presence of unexpected sample components, i.e., those not present in the calibration set. The model is based on a combination of residual bilinearization, which provides the second-order advantage, and kernel partial least-squares of unfolded data, a flexible non-linear version of partial least-squares. The latter one involves projection of the measured data onto a non-linear space, which in the present case consists of a set of Gaussian radial basis functions. Simulations concerning two ideal systems are analyzed: one where the signal-concentration relation is quadratic with positive deviations from linearity, and another one where it is sigmoidal. The results are favorably compared with those provided by several artificial neural network approaches. Two experimental systems are also studied, involving the analysis of: 1) the lipid degradation product malondialdehyde in olive oil samples, where the background oil provides a strong interferent signal, and 2) the antibiotic amoxicillin in the presence of the anti-inflammatory salicylate as interferent. The results for these experimental cases are also encouraging.Fil: Garcia Reiriz, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica; ArgentinaFil: Damiani, Patricia Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica; ArgentinaFil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica; Argentin

Comparative chemometric analysis of fluorescence and near infrared spectroscopies for authenticity confirmation and geographical origin of Argentinean extra virgin olive oils

Extra virgin olive oil (EVOO) is widely used in gastronomy because of its healthy properties, and is a candidate to be adulterated with other vegetable oils to reduce costs. This work shows the results of applying near infrared (NIR) and fluorescence excitation–emission matrix spectroscopies, coupled to chemometric tools, to authenticate and validate the geographic origin of Argentinean EVOO samples. For each spectral data set, principal component analysis (PCA) was applied to both first–order NIR and second–order fluorescence data, partial least squares–discriminant analysis (PLS1–DA) to NIR data, and the multidimensional version of the latter (NPLS–DA) to fluorescence data. The results of the study of sixty EVOO samples of known and unknown registered designation of origin (RDO), as well as artificial samples adulterated with other edible oils, showed that: (1) fluorescence spectroscopy was unable to determine the RDO of all EVOO samples, in contrast to NIR (100% classified correctly), and (2) fluorescence data provide only slightly better results than NIR spectroscopy to detect EVOO adulterations with other vegetable edible oils.Fil: Jiménez Carvelo, Ana M.. Universidad de Granada; EspañaFil: Lozano, Valeria Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

Aging of malbec wines from Mendoza and California: Evolution of volatile composition

Background and goals The search for strategies to improve the quality of Argentine Malbec wines has led to experimentation with production of wines that achieve superior sensory properties after prolonged bottle aging. During aging, a series of complex oxidation-reduction and polymerization reactions occur. These reactions, responsible for changing the sensory aspects of wines, can be influenced by a variety of factors (terroir, winemaking practices, storage conditions, etc.). Thus, understanding the chemical processes that take place during bottle aging could significantly impact the enology industry. This work evaluates the evolution of aromatic profiles over time in Malbec wines from Mendoza and California. Methods and key findings Wines from Mendoza and California were obtained under standardized conditions. Determination of volatile profiles was carried out on young wines by gas chromatography-mass spectrometry and, subsequently, after seven years of aging. The effect of time and region on volatile profiles was investigated. The aging time showed a significant effect on the aromatic composition. While the profiles obtained after seven years were less diverse than at bottling, they retained a significant number of desirable volatile compounds. Additionally, the volatile profiles of the aged wines still permitted differentiation of samples by region of origin. Conclusions and significance The information obtained enabled us to assess the evolution of aromatic profiles during bottle aging of Malbec wines from Mendoza and California, and could be useful in decision-making regarding the blending, marketing, and storage of these wines.Fil: Pellegrino Vidal, Rocio. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; Argentina. Catena Institute Of Wine.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Boulton, Roger B.. University of California at Davis; Estados UnidosFil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Buscema, Fernando. Catena Institute Of Wine.; Argentin

Design, characterization and in vitro evaluation of antifungal polymeric films

The objective of the present paper was the development and the full characterization of antifungal films. Econazole nitrate (ECN) was loaded in a polymeric matrix formed by chitosan (CH) and carbopol 971NF (CB). Polyethylene glycol 400 and sorbitol were used as plasticizing agents. The mechanical properties of films were poorer when the drug was loaded, probably because crystals of ENC produces network outages and therefore reduces the polymeric interactions between the polymers. Polymers–ECN and CH–CB interactions were analyzed by Fourier-transform infrared spectroscopy (FTIR), thermal gravimetry analysis, and differential thermal analysis (DTA-TGA). ECN did not show structure alterations when loaded into the films. In scanning electron microphotographs and atomic force microscopy analysis, films prepared with CB showed an evident wrinkle pattern probably due to the strong interactions between the polymers, which were observed by FTIR and DTA-TGA. The in vitro activity of the formulations against Candida krusei and Candida parapsilosis was twice as greater as the commercial cream, probably as a result of the antifungal combination of the drug with the CH activity. All these results suggest that these polymeric films containing ECN are potential candidates in view of alternatives dosages forms for the treatment of the yeast assayed.Fil: Real, Daniel Andres. Universidad Nacional de Rosario; ArgentinaFil: Martinez, Maria V.. Universidad Nacional de Rosario; ArgentinaFil: Frattini, Agustin Lujan. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; ArgentinaFil: Soazo, Marina del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; ArgentinaFil: Luque, Alicia G.. Universidad Nacional de Rosario; ArgentinaFil: Biasoli, Marisa S.. Universidad Nacional de Rosario; ArgentinaFil: Salomon, Claudio Javier. Universidad Nacional de Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; ArgentinaFil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; ArgentinaFil: Leonardi, Darío. Universidad Nacional de Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; Argentin

Recent advances in analytical calibration with multi-way data

This critical review discusses the advances which have taken place in recent years in the field of multi-way instrumental data, i.e., data that can be arranged into a mathematical object of at least three ways (when they are measured for a group of samples). Particular focus is directed towards research works describing quantitative analytical calibrations. The development of data processing algorithms and the estimation of figures of merit are reviewed, along with the progress in the experimental generation of new three-, four- and five-way data of spectroscopic, chromatographic and electrochemical origin.Fil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

Evaluation of the ambiguity in second-order analytical calibration based on multivariate curve resolution: A tutorial

The aims of the present tutorial are the following: (1) to show the importance of applying all the chemically sensible constraints which are necessary to retrieve interpretable component profiles when processing second-order analytical data with multivariate curve resolution – alternating least-squares (MCR-ALS), (2) to demonstrate that the constraints allow one to reduce or even remove the impact of the rotational ambiguity in the MCR-ALS solutions, and (3) to provide details on how to estimate the uncertainty in the predicted analyte concentrations which is derived from any remaining ambiguity with a recently developed N-BANDS method. Both simulated and experimental data sets are examined for this purpose. Recommendations are given for including the ambiguity uncertainty in addition to the statistical reports and analytical figures of merit in every MCR-ALS calibration protocol, to assess the reliability of the analytical results.Fil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

Introduction to multivariate calibration: A practical approach

This book offers an introductory-level guide to the complex field of multivariate analytical calibration, with particular emphasis on real applications such as near infrared spectroscopy. It presents intuitive descriptions of mathematical and statistical concepts, illustrated with a wealth of figures and diagrams, and consistently highlights physicochemical interpretation rather than mathematical issues. In addition, it describes an easy-to-use and freely available graphical interface, together with a variety of appropriate examples and exercises. Lastly, it discusses recent advances in the field (figures of merit, detection limit, non-linear calibration, method comparison), together with modern literature references.Fil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

Second-order multivariate calibration with the extended bilinear model: Effect of initialization, constraints, and composition of the calibration set on the extent of rotational ambiguity

Extended bilinear modeling is popular in second-order multivariate calibration, particularly when the matrix data for each sample are of chromatographic origin. Since elution time profiles vary across samples, in both shape and peak position, it is not possible to process these data in a three-way trilinear format. In these cases, the most successful model for quantitating analytes in the presence of interferents is multivariate curve resolution-alternating least squares (MCR-ALS) in its extended version, ie, processing an augmented data matrix built with the matrices for a test sample and the calibration samples, appended in the direction of the elution time mode. MCR-ALS starts with certain initial profiles and applies a set of natural constraints during the ALS phase, whose purpose is to reduce the range of feasible solutions or to lead to unique bilinear solutions if possible. In this report, a simulated second-order three-component system (two calibrated analytes and one uncalibrated interferent in test samples) is studied regarding the presence of rotational ambiguity in the bilinear solutions, using (a) a grid search methodology to compute the feasible solutions and (b) MCR-ALS on a large set of test samples to estimate the average prediction errors. Various initialization schemes and constraints are probed, and the results are compared in terms of the extent of rotational ambiguity and global uncertainty in predicted concentrations.Fil: Olivieri, Alejandro Cesar. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

A down-to-earth analyst view of rotational ambiguity in second-order calibration with multivariate curve resolution: a tutorial

Rotational ambiguity is a phenomenon with the potential of generating an uncertainty in the estimation of analyte concentrations in protocols based on matrix instrumental data processed by multivariate curve resolution - alternating least-squares (MCR-ALS). This is particularly relevant when the second-order advantage is to be achieved, i.e., when selected analytes are determined in unknown samples having unexpected constituents, not considered in the calibration set of samples. It is therefore imperative that analytical chemists developing second-order multivariate calibration methods using MCR-ALS acknowledge the relevance of this issue, and more importantly, have access to the required tools to size the relative impact of this potential source of uncertainty on the estimated analyte concentrations. The purpose of this tutorial is to provide a down-to-earth view of rotational ambiguity, by studying in detail a synthetic example mimicking a typical chromatographic-spectral experiment, where a set of calibration samples is joined with an unknown sample having an uncalibrated interference. After explaining the background information needed to understand the origin of the phenomenon, the available tools for the estimation of the feasible MCR-ALS solutions and the derived uncertainty on analyte predictions will be discussed. A multi-component experimental system will also be discussed, stressing the fact that rotational ambiguity uncertainties, however small, should always be estimated and reported.Fil: Olivieri, Alejandro Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin