Chemometrics-assisted excitation–emission fluorescence spectroscopy on nylon-attached rotating disks. Simultaneous determination of polycyclic aromatic hydrocarbons in the presence of interferences

This work presents a green and very simple approach which enables the accurate and simultaneous determination of benzo[a]pyrene, dibenz[a,h]anthracene, benz[a]anthracene, and chrysene, concerned and potentially carcinogenic heavy-polycyclic aromatic hydrocarbons (PAHs) in interfering samples. The compounds are extracted from water samples onto a device composed of a small rotating Teflon disk, with a nylon membrane attached to one of its surfaces. After extraction, the nylon membrane containing the concentrated analytes is separated from the Teflon disk, and fluorescence excitation–emission matrices are directly measured on the nylon surface, and processed by applying parallel factor analysis (PARAFAC), without the necessity of a desorption step. Under optimum conditions and for a sample volume of 25 mL, the PAHs extraction was carried out in 20 min. Detection limits based on the IUPAC recommended criterion and relative errors of prediction were in the ranges 20–100 ng L−1 and 5–7%, respectively. Thanks to the combination of the ability of nylon to strongly retain PAHs, the easy rotating disk extraction approach, and the selectivity of second-order calibration, which greatly simplifies sample treatment avoiding the use of toxic solvents, the developed method follows most green analytical chemistry principles.Fil: Cañas, Alejandro. Universidad de Chile. Facultad de Ciencias Químicas y Farmacéuticas. Departamento de Química Inorgánica y Analítica; Chile.Fil: Richter, Pablo. Universidad de Chile. Facultad de Ciencias Químicas y Farmacéuticas. Departamento de Química Inorgánica y Analítica; Chile.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

Determination of tributyltin at parts-per-trillion levels in natural waters by second-order multivariate calibration and fluorescence spectroscopy

This work presents a non-sophisticated approach for the trace determination of tributyltin, the most toxic organotin species, in very interfering environments, combining fluorescence measurements of its morin complex and the selectivity of second-order chemometric algorithms. The power of MCR–ALS (multivariate curve resolution/alternating least-squares) to quantify tributyltin through fluorescence excitation–emission matrices in the presence of its main degradation products and of a pool of additional twenty-three metal ions is demonstrated. The applied algorithm successfully faces the challenge of solving the strong overlapping among the spectra of the several sample components. The proposed methodology was applied to tap, river, lagoon and seawater spiked samples, obtaining satisfactory results at ngL −1 levels, after a pre-concentration step on a C18 membrane, demonstrating the analytical potential of the proposed methodology.Fil: Bravo, Manuel. Pontificia Universidad Católica de Valparaíso. Instituto de Química. Laboratorio de Química Analítica y Ambiental; Chile.Fil: Aguilar, Luis Felipe. Pontificia Universidad Católica de Valparaíso. Instituto de Química. Laboratorio de Fotofísica y Espectroscopia Molecular; Chile.Fil: Quiroz, Waldo. Pontificia Universidad Católica de Valparaíso. Instituto de Química. Laboratorio de Química Analítica y Ambiental; Chile.Fil: Olivieri, Alejandro César. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

Multivariate calibration-assisted high-performance liquid chromatography with dual UV and fluorimetric detection for the analysis of natural and synthetic sex hormones in environmental waters and sediments

A green method is reported based on non-sophisticated instrumental for the quantification of seven natural and synthetic estrogens, three progestagens and one androgen in the presence of real interferences. The method takes advantage of: (1) chromatography, allowing total or partial resolution of a large number of compounds, (2) dual detection, permitting selection of the most appropriate signal for each analyte and, (3) second-order calibration, enabling mathematical resolution of incompletely resolved chromatographic bands and analyte determination in the presence of interferents. Consumption of organic solvents for cleaning, extraction and separation are markedly decreased because of the coupling with MCR-ALS (multivariate curve resolution/alternating least-squares) which allows the successful resolution in the presence of other co-eluting matrix constituents. Rigorous IUPAC detection limits were obtained: 6–24 ng L−1 in water, and 0.1–0.9 ng g−1 in sediments. Relative prediction errors were 2–10% (water) and 1–8% (sediments).Fil: Pérez, Rocío Laura. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

Liquid chromatography with diode array detection and multivariate curve resolution for the selective and sensitive quantification of estrogens in natural waters.

Following the green analytical chemistry principles, an efficient strategy involving second-order data provided by liquid chromatography (LC) with diode array detection (DAD) was applied for the simultaneous determination of estriol, 17β-estradiol, 17α-ethinylestradiol and estrone in natural water samples. After a simple pre-concentration step, LC-DAD matrix data were rapidly obtained (in less than 5 min) with a chromatographic system operating isocratically. Applying a second-order calibration algorithm based on multivariate curve resolution with alternating least-squares (MCR-ALS), successful resolution was achieved in the presence of sample constituents that strongly coelute with the analytes. The flexibility of this multivariate model allowed the quantification of the four estrogens in tap, mineral, underground and river water samples. Limits of detection in the range between 3 and 13 ng L−1, and relative prediction errors from 2 to 11% were achieved.Fil: Pérez, Rocío Laura. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

Spectroflurimetric study of estrogen-cyclodextrin inclusion complexes in aqueous systems

For the first time, the spectrofluorimetric properties of estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethinylestradiol (EE2) are studied in aqueous solutions after the addition of native and derivative cyclodextrins. In contrast to previous reports, the behavior of the systems is analysed in the absence of organic solvents able to modify the guest-host interaction. The significant differences between the obtained association constants with those reported in solvent mixtures are shown and discussed. In order to evaluate the influence of both the estrogen structure and the presence of cyclodextrin substituents in the inclusion phenomena, fluorescent and acid-base behaviors of the systems are compared and discussed. The interaction of estrogens with micellar media formed by selected surfactants is also studied. It is demonstrated that estrogen-cyclodextrin complexes in aqueous solution are useful for improving fluorimetric detection limits and, since cyclodextrins are non-toxic and mitigate most of the solubility problems which require the use of organic solvents, the studied complexes are excellent candidates for extraction, separation, pre-concentration and removal processes maintaining the principles of the green analytical chemistry

Second-order advantage with excitation–emission photoinduced fluorimetry for the determination of the antiepileptic carbamazepine in environmental waters

A photochemically induced fluorescence system combined with second-order chemometric analysis for the determination of the anticonvulsant carbamazepine (CBZ) is presented. CBZ is a widely used drug for the treatment of epilepsy and is included in the group of emerging contaminant present in the aquatic environment. CBZ is not fluorescent in solution but can be converted into a fluorescent compound through a photochemical reaction in a strong acid medium. The determination is carried out by measuring excitation–emission photoinduced fluorescence matrices of the products formed upon ultraviolet light irradiation in a laboratory-constructed reactor constituted by two simple 4 W germicidal tubes. Working conditions related to both the reaction medium and the photoreactor geometry are optimized by an experimental design. The developed approach enabled the determination of CBZ at trace levels without the necessity of applying separation steps, and in the presence of uncalibrated interferences which also display photoinduced fluorescence and may be potentially present in the investigated samples. Different second-order algorithms were tested and successful resolution was achieved using multivariate curve resolution-alternating least-squares (MCR-ALS). The study is employed for the discussion of the scopes and yields of each of the applied second-order chemometric tools. The quality of the proposed method is probed through the determination of the studied emerging pollutant in both environmental and drinking water samples. After a pre-concentration step on a C18 membrane using 50.0 mL of real water samples, a prediction relative error of 2% and limits of detection and quantification of 0.2 and 0.6 ng mL−1 were respectively obtained.Fil: Lozano, Valeria Antonella. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); ArgentinaFil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

Experimental and chemometric strategies for the development of Green Analytical Chemistry (GAC) spectroscopic methods for the determination of organic pollutants in natural waters

The development of Green Analytical Chemistry (GAC) methods is one of the most active areas of Green Chemistry. Especially relevant are GAC methods devoted to the detection and quantification of environmental pollutants, because they should not pollute the environment more than the analyte to be determined. While considerable attention has been paid to develop environmentally friendly alternatives for the first stage of the global analytical process (e.g., sample preparation techniques), relatively fewer works are dedicated to implement green approaches for obtaining the analytical signal. Current strategies that are based on the principles of Green Chemistry for the determination of common organic pollutants in natural waters are detailed. The review collects and discusses selected publications from about the last 5 years relating to the topic, highlighting the role of multivariate calibration as a modern and very useful tool to achieve the pursued objectives.Fil: Pérez, Rocío Laura. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

Second-order chromatographic photochemically induced fluorescence emission data coupled to chemometric analysis for the simultaneous determination of urea herbicides in the presence of matrix co-eluting compounds

This paper presents a novel approach for the simultaneous determination of isoproturon, rimsulfuron and monuron, three widely used urea-derivative herbicides, in interfering environmental samples, combining the advantages of photoinduced fluorescence (PIF) emission, liquid chromatography and second-order chemometric algorithms. Chromatographic detection is performed with a fast-scanning spectrofluorimeter, which allowed efficient collection of PIF through a post-column photoreactor. Thus, second-order elution time-PIF emission data matrices are rapidly obtained (in less than 4 min) using a chromatographic system operating in an isocratic regime using a minimal amount of organic solvent. The goal of the present study was the successful resolution of a system in the presence of foreign compounds which can be present in real samples. The study was employed for the discussion of the scope of the applied second-order algorithms selected for data processing, namely parallel factor analysis (PARAFAC), multivariate curve resolution-alternating least-squares (MCR-ALS), and multidimensional and unfolded partial least-squares coupled to residual bilinearization (N- and U-PLS/RBL). U-PLS/RBL showed the best performance to quantify the herbicides, even when the foreign compounds showed very similar spectral and time profiles to the analytes. The quality of the proposed technique was assessed on the basis of the analytical recoveries from different types of water samples spiked with analytes and other selected agrochemicals. After solid-phase extraction, reaching a preconcentration factor of 50, detection limits of 2.9, 2.4, and 1.7 ng mL−1 for isoproturon, rimsulfuron, and monuron, respectively, were obtained in those interfering matrices, with relative prediction errors lower than 5%.Fil: Arancibia, Juan Alberto. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

A green-analytical chemistry method for agrochemical-residue analysis in vegetables

Ten agrochemicals, including fungicides, insecticides, herbicides and a plant growth regulator, were quantified at part per billion levels in complex matrices using a green-analytical chemistry (GAC) method. Liquid chromatography with dual UV/diode array (DAD) and fluorescence (FLD) detections was carried out in a single run, and the second-order DAD-elution time and FLD-elution time data obtained were treated with MCR-ALS (multivariate curve resolution/alternating least-squares) algorithm. In this way, while analytes are measured through their more appropriate (absorbance and/or fluorescence) signals, chemometric treatment of the corresponding matrices allows the resolution of total or partial overlapped bands, and to overcome the presence of interferences in real samples. In this work, FLD-elution time second-order data were obtained for the first time at two excitation wavelengths, improving the sensitivity of fluorescent analytes. The approach was successfully applied to in land cultivated vegetables, including mushroom, lettuce, alfalfa sprout, cucumber, and celery.Fil: Carabajal, Maira Daniela. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Arancibia, Juan Alberto. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina

A Critical Review on the Development of Optical Sensors for the Determination of Heavy Metals in Water Samples. The Case of Mercury(II) Ion

Recent publications are reviewed concerning the development of sensors for the determination of mercury in drinking water, based on spectroscopic methodologies. A critical analysis is made of the specific details and figures of merit of the developed protocols. Special emphasis is directed to the validation and applicability to real samples in the usual concentration range of mercury, considering the maximum allowed limits in drinking water established by international regulations. It was found that while most publications describe in detail the synthesis, structure, and physicochemical properties of the sensing phases, they do not follow the state of the art in the analytical developments. Recommendations are provided regarding the proper method development and validation, including the setting of the calibration concentration range, the correct estimation of the limits of detection and quantitation, the concentration levels to be set for producing spiked water samples, the number of real samples for adequate validation, the comparison of the developed method with a reference technique, and other analytical features which should be followed.Fil: Escandar, Graciela Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Olivieri, Alejandro César. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica. Instituto de Química Rosario (IQUIR-CONICET); Argentina