Mercedes Villar Navarro

Electromembrane extraction (EME) and HPLC determination of non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater samples.

In this paper, an electromembrane extraction (EME) combined with a HPLC procedure using diode array (DAD) and fluorescence detection (FLD) has been developed for the determination of six widely used non-steroidal anti-inflammatory drugs (NSAIDs): salicylic acid (SAC), ketorolac (KTR), ketoprofen (KTP), naproxen (NAX), diclofenac (DIC) and ibuprofen (IBU). The drugs were extracted from basic aqueous sample solutions, through a supported liquid membrane (SLM) consisting of 1-octanol impregnated in the walls of a S6/2 Accurel(®) polypropylene hollow fiber, and into a basic aqueous acceptor solution resent inside the lumen of the hollow fiber with a potential difference of 10 V applied over the SLM. Extractions that were carried out in 10 min using a potential of 10 V from pH 12 NaOH aqueous solutions shown concentration enrichments factors of 28-49 in a pH 12 NaOH aqueous acceptor solution. The proposed method was successfully applied to urban wastewaters. Excellent selectivity was demonstrated as no interfering peaks were detected. The procedure allows very low detection and quantitation limits of 0.0009-9.0 and 0.003-11.1 μg L(-1), respectively.

Hollow fiber-based liquid phase microextraction (HF-LPME) for a highly sensitive HPLC determination of sulfonamides and their main metabolites

In this paper, three phase-hollow fiber-based liquid phase microextraction (HF-LPME) combined with a HPLC procedure using diode array (DAD) and fluorescence detection (FLD) has been developed for the determination of four widely used sulfonamides: sulfadiazine, sulfamerazine, sulfamethazine, sulfamethoxazole and their main metabolites, the corresponding N(4)-acetyl derivatives: N(4)-acetyl-sulfadiazine, N(4)-acetyl-sulfamerazine, N(4)-acetyl-sulfamethazine, N(4)-acetyl-sulfamethoxazole. A Q3/2 Accurel KM polypropylene hollow fiber supporting 1-octanol was used between a 2 M Na(2)SO(4) aqueous solution (pH 4) as a donor phase and aqueous solution (pH 12) as an acceptor phase. The procedure allows very low detection and quantitation limits of 0.3-33 ng L(-1) and 0.9-100 ng L(-1), respectively. The proposed method was applied to the determination of the analytes in environmental water samples (surface, tap and wastewater).

Application of chemiluminescence in the analysis of wastewaters – A review

The toxicological effects of diverse pollutants typically found on wastewaters of diverse origin (industrial, urban, etc.) have led to regulation of their emission by national and trans-national organizations, and an increasing interest in the development of fast and reliable methods for their analysis. This paper is an up-to-date comprehensive review on the analytical applications of chemiluminescence technique (characterized by high sensitivity, wide dynamic ranges and simple instrumentation) to the analysis of wastewaters, emphasizing the different kinds of pollutants that have been studied with these methods and discussing the different approaches followed by the authors as CL reactions, devices and coupled methods.

Hollow fiber-based liquid-phase microextraction (HF-LPME) of ibuprofen followed by FIA-chemiluminescence determination using the acidic permanganate―sulfite system

Hollow fiber-based liquid-phase microextraction (HF-LPME) is a relatively new technique employed in analytical chemistry for sample pretreatment which offers more selectivity and sensitivity than any traditional extraction technique. This paper describes a three-phase HF-LPME method for ibuprofen using a polypropylene membrane supporting dihexyl ether followed by a chemiluminescence (CL) determination using the CL enhancement on the acidic permanganate-sulfite system in a FIA configuration which is the first time that both techniques have been combined for analytical purposes. The CL intensity (peak area) was proportional to the log of ibuprofen concentration in the donor phase over the range 0.1-20 microg mL(-1). The detection limit was 0.03 microg mL(-1) of ibuprofen in the donor phase. The method was satisfactory reproducible and has been applied to the ibuprofen determination in pharmaceuticals and in real human urine samples.

Capillary electrophoresis determination of nonsteroidal anti‐inflammatory drugs in wastewater using hollow fiber liquid‐phase microextraction

The presence of pharmaceuticals in the environment due to growing worldwide consumption has become an important problem that requires analytical solutions. This paper describes a CE determination for several nonsteroidal anti‐inflammatory drugs (ibuprofen, naproxen, ketoprofen, diclofenac, ketorolac, aceclofenac and salicylic acid) in environmental waters using hollow fiber membrane liquid‐phase microextraction. The extraction was carried out using a polypropylene membrane supporting dihexyl ether and the electrophoretic separation was performed in acetate buffer (30 mM, pH 4) using ACN as the organic modifier. Detection limits between 0.25 and 0.86 ng/mL were obtained, respectively. The method could be applied to the direct determination of the seven anti‐inflammatories in wastewaters, and five of them have been determined or detected in different urban wastewaters.

Dual CD system-modified MEEKC method for the determination of clemastine and its impurities

A dual system of CDs was used for the first time in MEEKC with the aim of determining clemastine and its three main related impurities in both drug substances and tablets. The addition of methyl‐β‐cyclodextrin and heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin to the microemulsion pseudo‐stationary phase was essential to increase the resolving power of the system to obtain a baseline separation among the compounds. The best microemulsion composition was identified by mixture design and the effects of the factors concentrations of CDs and voltage were investigated by a response surface study applying a Central Composite Design. In both cases, Derringers desirability function made it possible to find the global optimum, which corresponded to the following combination: microemulsion, 89.8% 10 mM borate buffer pH 9.2, 1.5% n‐heptane and 8.7% of SDS/n‐butanol in 1:2 ratio; 18 mM methyl‐β‐cyclodextrin, 38 mM heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin, 17 kV. By applying these conditions, the separation was completed in about 5.5 min. The method was validated following International Conference on Harmonisation guidelines and was applied to a real sample of clemastine tablets.

Optimisation and validation of a new CE method for the determination of lansoprazole enantiomers in pharmaceuticals

An analytical method based on CZE to determine lansoprazole enantiomers in pharmaceuticals was developed. The primary factors affecting its separation efficiency, which include chiral selector, pH, buffer concentration, capillary temperature and injection time, were optimised. The best results were obtained by using a background electrolyte consisting of 50 mM phosphate adjusted to pH 2.2, 12 mM β‐CD and 5 mM sodium sulphite, in combination with hydrodynamic injection and a 15 kV separation voltage. Detection limits were calculated from baseline noise and found to be 0.64 mg L−1 for the R enantiomer and 0.72 mg L−1 for the S enantiomer. The proposed method was used to analyse three different pharmaceutical preparations with recoveries of 91–102% of the label content.

Rapid Flow-Injection Method for the Determination of Colistin by Sensitized Chemiluminescence Using the Acidic Permanganate–Sulfite System

Abstract A simple, rapid, and sensitive chemiluminescence method for the determination of colistin (Polymyxin E), a cyclic polypeptide with antibiotic effect produced by certain strains of Bacillus polymyxa, has been developed by combining a flow-injection technique and the bacterias sensitizing effect on the chemiluminescence reaction between sulfite and acidic permanganate. The optimum conditions for chemiluminescence emission were established. The chemiluminescence was proportional to the log of concentration of colistin over the range 4–100 µg mL−1 (3.5–87 µM). The detection limit was 1.2 µg mL−1 (1.0 µM) of colistin. The method has been satisfactorily used for the determination of colistin in pharmaceuticals.

Simultaneous Determination of Pesticides in Fruits by Using Second-Order Fluorescence Data Resolved by Unfolded Partial Least-Squares Coupled to Residual Bilinearization

In the present work, a chemometric-assisted spectrofluorimetric method has been developed for the simultaneous determination of natural fluorescent pesticides, carbaryl, carbendazim, and thiabendazole, in orange and banana. Only a simple extraction with methanol was required as sample pretreatment. Emission-excitation fluorescence matrices were obtained and resolved by using a second-order multivariate calibration method based on unfolded partial least-squares combined with residual bilinearization (U-PLS/RBL) for achieving “second-order advantage.” In this way, pesticides were determined in fruits even in the presence of inner filter effects, background interactions, strong spectral overlapping, and unexpected components. U-PLS can cope with effects that cause trilinearity loss such as, inner filter effects, including background in the calibration set; meanwhile, RBL allows to resolve the presence of unexpected components. The extraction technique was validated against a commonly applied technique based on the use of ethyl acetate and sodium sulfate. Besides, results obtained for real samples were statistically compared with those obtained by using HPLC. LODs of 0.038, 0.054, and 0.018 mg·kg−1 and 0.044, 0.072, and 0.020 mg·kg−1 were obtained for carbaryl, carbendazim, and thiabendazole in banana and orange samples, respectively; values were in accordance with the MRLs (Maximum Residue Limits) established by different official control organizations such as National Food Safety and Quality Service (SENASA), Codex Alimentarius (based on Food and Agriculture Organization (FAO) of the United Nations and World Health Organization (WHO), and Environmental Protection Agency (EPA).

Desarrollo de líneas experimentales para su aplicación en los Trabajos de Fin de Grado en Química

Desde el punto de vista academico, los Trabajos Fin de Grado en Ciencias Quimicas se presentan como proyectos experimentales relacionados con problemas reales, orientados a progresar en conocimientos y fortalecer competencias adquiridas, convirtiendose en claves del curriculo para el mundo profesional. Se abordan una serie de proyectos de laboratorio como una aproximacion mas realista al aprendizaje integral. La metodologia docente propuesta favorece la busqueda de informacion, pensamiento critico, superacion continua y exito de los estudiantes, similar a la que se realiza en el mundo real, estimulando su interes y motivacion durante el proceso de aprendizaje.