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Recibido: 07 de diciembre de 2021.Aprobado: 07 de marzo de 2022. En este trabajo, se caracterizó el color de hilos de lana teñida artesanalmente en dos periodos (campañas 2014 y 2015) utilizados en la confección de sarapes de Saltillo, en México. El análisis espectral se hizo por Espectrofotometría UV-Vis de Reflectancia Difusa; el análisis cromático se realizó en el espacio de color CIELAB, utilizando el iluminante estándar D65 y el observador a 10 grados, a partir de los espectros de reflectancia. Una vez identificadas las coordenadas cromáticas, se convirtieron a los colores correspondientes mediante la ayuda de software. Finalmente, se calcularon los valores de ∆ECMC para reconocer las variaciones de color entre hilos del mismo tono, con distintas luminosidades y saturaciones, encontrando que en algunos casos los valores registrados correspondieron a variaciones apenas perceptibles por el ojo humano, lo cual es un parámetro de calidad en la confección de estos textiles, emblemáticos de la cultura mexicana. Con ello, se busca registrar las características colorimétricas típicas de estas artesanías, con el fin de coadyuvar a su protección intelectual y preservación.

Bivariate calibration algorithm is compared with the results obtained by the usage of high-dimensional calibration methods such as partial least squares (PLS) and multi-way partial least-squares (N-PLS) by using UV-Vis spectrophotometric data of first and second-order. The algorithms were applied to the determination of a mixture of an analgesic and a stimulant compound and their actual concentrations of them were calculated by using spectroscopic data. The direct reading of absorbance values at 227 nm and 271 nm were employed for quantification of the compounds in the case of the bivariate method. The approaches of first-order and multi-way methods were applied with a previous optimization of the calibration matrix by constructing sets of calibration and validation with 20 and 10 samples (mixtures) respectively according to a central composite design and their UV absorption spectra were recorded at 200-350 nm. All algorithms were satisfactorily applied to the simultaneous determination of these compounds in pharmaceutical formulations with mean percentage recovery of 100.5 ± 3.67, 98.7 ± 3.42, and 100.5 ± 3.74 for bivariate, PLS-1, and N-PLS, respectively. The statistical evaluation of the bivariate method showed that this procedure is comparable with those algorithms that employ high-dimensional structured information. The aim of the work is to compare the methods under study and it can be seen that there are no significant differences, so a simple spectrophotometer can be used up to a very specialized one. However, the advantage of bivariate calibration is its simplicity, due to the minimal experimental manipulation.

Herein, the electrochemical behavior of the simetryn herbicide at the water|1,2-dichloroethane interface was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Parameters such as transfer Gibbs energy, ionic partition coefficient, and the apparent rate constants across the interface were evaluated. According to the results, the ionic form of this herbicide is highly hydrophobic because Δw o G0 SIMH w→o + is 3.57 kJ mol−1 and logPSIMH 0 + is −0.622. In addition, the ionic partition diagram for this compound shows dual behavior as a function of pH: when pH < pKa, simetryn is transferred as a whole protonated molecule across the interface; whereas, when pH > pKa, simetryn serves as a mobile proton carrier across the interface. The present study offers some important insights that help in understanding the partitioning and kinetic processes of environmentally important molecules across biological membranes. Fil: Velázquez-Manzanares, Miguel. Universidad Autonoma de Coahuila; México Fil: García Martínez, Humberto. Universidad Autonoma de Coahuila; México Fil: Yudi, Lidia Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Amador-Hernández, Judith. Universidad Autonoma de Coahuila; México Fil: de la Garza Rodríguez, Iliana M.. Universidad Autonoma de Coahuila; México Fil: Colunga Urbina, Edith M.. Universidad Autonoma de Coahuila; México

Resumen En este trabajo, se caracterizó el color de lacas acrílicas blancas utilizadas para retocar pintura automotriz, mediante el espacio de color CIELab y el índice de blancura, utilizando el iluminante estándar D65 y el observador estándar a diez grados. A partir de tal información, fue posible reconocer las tendencias del color usado en este tipo de productos en el mercado nacional. Por otra parte, la aplicación de las técnicas quimiométricas de Análisis de Componentes Principales, Análisis de Grupos y Análisis Jerárquico, permitió reconocer semejanzas entre los colores observados, encontrando, entre otros, la mayor diferencia visual en la laca de blanco aperlado. Por otro lado, la laca de blanco Alaska de Mazda y la de blanco universal de Nissan fueron las más parecidas. También se concluye que el análisis cromático y el quimiométrico de datos espectrales fueron complementarios, por lo que se recomiendan ambos en el nivel de control de calidad. Abstract The color of white acrylic lacquers utilized to touch up automotive paint was characterized in this paper using the CIELab color space and the whiteness index, with standard illuminant D65 and the standard observer at ten degrees. Based on this information, the color trends used in this type of product in the national market were recognized. In addition, the chemometric techniques of the Principal Component Analysis, Cluster Analysis, and Hierarchical Analysis allowed for recognition of similarities between the observed colors, which found, among other aspects, the greatest visual difference in the pearl white lacquer. On the other hand, the Alaskan white lacquer from Mazda and the universal white lacquer from Nissan were the most similar. It is also concluded that the chromatic and chemometric analyses of spectral data complemented each other; therefore, both are recommended for quality control purposes. Resumo Neste trabalho, caracterizou-se a cor de lacas acrílicas brancas utilizadas para retocar pintura automotriz, através do espaço de cor CIELab e o índice de brancura, utilizando o iluminador padrão D65 e o observador padrão a 10 graus. A partir dessa informação, foi possível reconhecer as tendências da cor usada neste tipo de produtos no mercado nacional. Por outro lado, a aplicação das técnicas quimiométricas de Análise de Componentes Principais, Análise de Grupos e Análise Hierárquica permitiu reconhecer semelhanças entre as cores observadas, encontrando, entre outras, a maior diferença visual na laca de branco perolizado. Por sua vez, a laca do branco Alaska da MAZDA e a do branco universal da NISSAN foram as mais parecidas. Conclui-se, também, que a análise cromática e a quimiométrica de dados espectrais foram complementárias, razão pela qual, em nível de controle de qualidade, ambas são recomendadas.

The electrochemical behavior of the metamitron herbicide at the water|1,2-dichloroethane interface was studied by means of cyclic voltammetry and Electrochemical Impedance Spectroscopy. The results show that metamitron extraction across the interface was pH dependent. The curves capacitance-potential shown that the presence of a lipid monolayer inhibits the metamitrone transport across the interface. In this paper the equilibrium partition of metamitron across the interface of two immiscible electrolyte solutions is discussed.

In this work, chemometric tools were applied to establish correlations between biomarkers and to identify the most significant ones in relation to acute exposure of Wistar rats to Pb. The metal content in biological matrices (serum, urine, liver, brain, and kidney), biochemical parameters (protein content, activity of the Glutathione S–Transferase enzymes, and urinalysis), apart from morphological measurements of organisms, were estimated in both the exposed and the control groups and submitted to Significance tests, Principal Component Analysis, Hierarchical Cluster Analysis, and Generalized Procrustean Analysis. It could be observed that Pb in serum, but not in erythrocytes, was the biomarker associated with the Pb content in kidney and other parameters related to this organ. In the same way, Pearson correlation coefficients emphasized the relation between Pb in serum and these variables, with the exception of kidney weight. Additionally, Pb in serum was found to be the biomarker with the greatest difference between the control and the exposed groups, which converts it into the most sensitive biomarker in the present study.

In this work, principal component regression and partial least squares regression were used for the estimation of acid dissociation constants through UV-Vis spectrophotometric measurements, considering five well-known acid-base indicators as well as two herbicides as analytes. In each case, an acid-base titration was carried out. Then, the multivariate calibration model was constructed with a few absorption spectra of the series at extreme pH values, to which values of the dissociation fraction (α) of 1 or 0 were assigned, in the case of HA or Aspecies. After that, the prediction step consisted in the estimation of α for the rest of the series. Then, distribution diagrams were built up with α vs pH, to find α = 0.5 where pH = pK a . The results were compared with those obtained through multivariate curve resolution-alternating least squares and program stability quotients from absorbance data (SQUAD), which showed an excellent correspondence.

The quantification of lead in water samples is presented at the sub-ppb level through preconcentration with cloud point extraction (using Triton x-100 and eriochrome black T) and atomic absorption spectrometry with electrothermal atomization. In order to study the influence of several variables, experimental design analyses were carried out. Linearity was observed between 0.15 to 1.20 ng mL−1 (r = 0.98), with a detection limit of 0.04 ng mL−1 and a quantification limit of 0.15 ng mL−1. A mean recovery of 90 ± 9% (n = 6, P = 0.05) was found; at the precision was 9% expressed as the coefficient of variation. Anions and cations that were studied did not affect the recovery of lead. Water samples of different sources were analyzed directly as well as by the standard addition method; no statistical differences were found between the two procedures. Finally, the present methodology was compared with liquid–liquid extraction of the lead-ditizone complex, using green analytical indicators proposed for this purpose.

2012, Volume 159, Issue 11, Pages H893-H898. J. Electrochem. Soc. F. J. Barrera-Cruz, J. Amador-Hernandez and M. Velazquez-Manzanares ''Lasalocid A'' at the Water/1,2-dichloroethane Interface Electrochemical Investigation of the Ionophore Carboxylic service Email alerting click here in the box at the top right corner of the article or Receive free email alerts when new articles cite this article sign up

A new spectrophotometric method is presented for the automated differentiation of chloro- (0.5 to 5.0 mg/mL), thio- (0.5 to 5.0 mg/mL) and methoxy-triazines (1 to 10 mg/mL) in water samples. Classification models obtained by K-nearest neighbours, Soft Independent Modeling of Class Analogy, and Partial Least Squares-Discriminatory Analysis were constructed from zero order and first derivative absorption spectra as independent variables, in the spectral range from 210 to 270 nm. Binary responses were used as classifying variables (with/without certain group of triazines). With this dichotomous structure, parameters related to 2x2 contingency tables were used to evaluate the performance of the models. For tap and well water samples, sensitivity and selectivity values equal or higher than 50 % were obtained from autoscaled first derivative spectra, discriminated by Partial Least Squares-Discriminatory Analysis.

Bisphenol A (BPA) is a synthetic monomer used in the production of polycarbonate plastics, epoxy resins, among others; therefore, it is usually founded in food and beverage containers, dental sealants, etc. In 2003, more than 6 billion pounds of this compound were produced around the world, while the EPA estimates that at least 1 million pounds arrive in the environment each year. On the other hand, endocrine alterations in human beings have been associated with BPA due to its estrogenic capacity; the high hydrophobicity of the compound aids to go through biological membranes. For this reason, it is important to study the interfacial behavior of BPA in a dynamic model system as the interface between two immiscible electrolyte solutions (ITIES). The aim of this work was to study the inhibitory effect of bisphenol A on the transfer of the cation tetraethylammonium (TEA+) a cross the interface water|1,2-dichloroethane (1,2-DCE). The electrochemical experiments were carried out in a 4-electrode cell (two references and two counterelectrodes) and the interface was polarized by cyclic voltammetry (CV) and square wave voltammetry (SWV). According to the results, the BPA acts as an inhibitor of the transfer of the TEA+ at the water|1,2-DCE interface. Due to the high hydrophobicity of the BPA, this compound reaches the interface on the side of the organic phase and is accumulated. The discussion is focus on the diffusion coefficient values of the TEA+ (DTEA+) across the interface, since the DTEA+ decreases as a function of the BPA concentration. This study assisted to understand the way in which this compound is accumulated in living systems.

The electrochemical techniques are useful tools for the extraction of heavy metals from aqueous effluents. Between them, studies at the interface of two immiscible electrolyte solutions (ITIES) allow to understand the fundamentals that regulate the process of ionic metal extraction through hydrophobic barriers, owing to it is possible to control the equilibrium of the metal ion across the interface by applying an electrical potential. In the present work, it was studied the kinetic process of the facilitated ionic metal transfer by dibenzo-18-Crown-6 and diciclohexane-18-Crown-6 at the water/1,2-dioclhoroetane (1,2-DCE) interface The electrochemical experiments were carried out in a 4-electrode cell (two references and two counterelectrodes) and the interface was polarized by cyclic voltammetry (CV). The rate constant (k) for the facilitated metal transfer at the water/1,2-DCE interface was evaluated from CV data through the procedure proposed by Nicholson. The peak-to-peak separation (DEp) of the transfer from the aqueous to the organic phase and from organic to the aqueous phase wave, as well as the diffusion coefficient, were considered for the calculus of k. The results showed that k is in the range of 10-3 cms-1, which is according to the values previously obtained for ion transfers at the liquid-liquid interface.

Two diazadibenzocrown ethers (4,10-diazadibenzo-18-crown-6 and 4,10-diazadi(4'-tert-butylbenzo)-18-crown-6) have been studied as Pb2+, Cd2+ and Zn2+ carriers across the interface between two immiscible electrolyte solutions by cyclic and square wave voltammetry. These two ionophores were useful in assisting Pb2+, Cd2+ and Zn2+ transfer across the water/1,2- dichloroethane interface in reversible ion transfer processes. The facilitated transport of Pb2+ across this interface is easier than the transfer of the other two metal ions studied regarding the energetic of the two different ionophore facilitated processes. These properties make possible to use these hydrophobic ligands as extractants in solvent extraction systems as well as to mimicking the heavy metal transfer across biological membranes.

The kinetics of facilitated proton transfer by polyether 18-crown-6 across the water-1,2-dichloroethane interface has been investigated by cyclic voltammetry and ac impedance. It was found that rate apparent constant is quite similar for the several concentrations of 18-crown-6 used in the experiments, the rate constant values (k s ) were in the range: 0.028, 0.031, 0.027, and 0. 03 cm/s for 0.1, 0.15, 0.2, and 0.25 mM of 18-crown-6. A formal transfer potential of Δ0 wϕi 0′= 0.01 V was found for the facilitated proton transfer by 18-crown-6 at the water-1,2-dichloroethane interface; this value remained constant in the range of concentration considered in this work. According to the kinetic results, an interfacial reaction between the proton and the polyether 18-crown-6 is discussed in which the polyether does not transfer into the aqueous phase, in the time scale of the experiments. As a consequence, it can be concluded that the solvation and desolvation of ligand and proton play an important role in the rate-determining step.

The Kool-Aid powders (Kraft General Foods) contain one or two of the following dyes: Allura Red (FD and C Red-40, R40), Sunset Yellow (FD and C Yellow-6, Y6) Tartrazine (FD and C Yellow-5, Y5), Erythrosine B (FD and C Red-3, R3), Amaranth (FD and C Red-2, R2) and Brilliant Blue FCF (FD and C Blue 1, B1), depending on the taste of the drink. In this work the “universal” calibration matrix is proposed for the determination of R40 in soft drink powders by partial least squares method using Spectrophotometric data. The training set of samples consists of 23 solutions: three of them contain only R40 at different concentrations and the rest of them are the binary mixtures of R40 with one of the following dyes: R3, R2, Y5 or Y6; all at the concentrations varying in the range 2–22 mg l−1 (exception: R3 2–12 mg l−1). The good analytical performance of R40 calibration was obtained (R2 = 0.9993, RMSD = 0.2125, REP = 2.20%) and this calibration matrix was applied to the analysis of the real samples containing only one dye (R40) and to the samples containing also other dyes, commonly used as the color additives in drink powders. The results obtained were compared with the results of the official spectrophotometric method and with the results of PLS algorithm for different binary dye calibration matrices. A good statistical agreement was obtained in each case, which confirms that some interferences occurring in Spectrophotometric determinations can be eliminated using PLS algorithm and including some possibly interfering compounds in calibration samples.

The electrochemical behavior of the new ionophore N,N-di(methylenecarboxyethoxy) 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (DIAZ18C6) at the water|1,2-dichloroethane (1,2-dichloroethane= 1,2-DCE) interface was studied by means of cyclic and square wave voltammetry techniques. DIAZ18C6 was able to transfer Pb 2+ , Zn 2+ , and Cd 2+ across the interface and stoichiometries of 1:1 (Pb 2+ ,Zn 2 ) and 1:2 (Cd 2+ ) were found. DIAZ18C6 is highly soluble in 1,2-DCE; this mean that an interfacial complex formation takes place at the interface. These studies showed that a facilitated transfer of Ph 2+ requires less energy to be transferred from water to the organic phase than the facilitated transfer of Zn 2+ and Cd 2+ across the water | 1,2-DCE interface. As a consequence, this ligand showed selectivity for Pb 2+ over the other studied cations. The present work could contribute to a better understanding of the transfer of heavy metal in a biological cell or of selective metal extraction.

A group of herbicides of the triazine family (atrazine, simazine, ametryn, prometryn, atratone, and terbutryn) at the water/1,2-dichloroethane interface has been investigated by cyclic voltammetry. The formal transfer energy (Δ w o G o t,i ) was evaluated in acidic conditions (pH < pK w a ). It was found that the chemical structure determines the transfer of these herbicides at the liquid-liquid interface. For thiotriazines the values of Δ w o G o t,i are smaller than for chlorotriazines, indicating that the thiotrizines have more ability to protect the charge in the center of the molecule when it transfers across the interface than chlorotrizines. Ionizable triazine partition diagrams (potential vs pH) demonstrated that for all herbicides two transfer mechanisms were observed: facilitated proton transfer and ion transfer across the interface.

It is presented the development of a new and easy analytical method for the simultaneous determination of atrazine and dicamba in water. Under the experimental conditions proposed, atrazine showed a linear dynamic range of 0.3 to 4.9 µg mL-1, a limit of detection of 0.1 µg mL-1 and a limit of quantification of 0.3 µg mL-1; similarly, dicamba showed a linear dynamic range of 0.8 to 8.8 µg mL-1, a limit of detection of 0.2 µg mL-1 and a limit of quantification of 0.8 µ mL-1. Partial Least Squares Regression (Type 1) was applied for the resolution of spectral interferences between analytes, obtaining recovery percentages higher than 95 % for both compounds in synthetic mixtures. Finally, quantitative determination of both herbicides in tap, well and sea water samples, was carried out successfully by the proposed method, previous preconcentration of the analytes by solid phase extraction