Piedad Parrilla Vázquez

Simple, rapid, and sensitive determination of beta-blockers in environmental water using dispersive liquid–liquid microextraction followed by liquid chromatography with fluorescence detection

A novel method, dispersive liquid-liquid microextraction combined with liquid chromatography-fluorescence detection is proposed for the determination of three beta-blockers (metoprolol, bisoprolol, and betaxolol) in ground water, river water, and bottled mineral water. Some important parameters, such as the kind and volume of extraction and dispersive solvents, extraction time, pH, and salt effect were investigated and optimized. In the method, a suitable mixture of extraction solvent (60 μL carbon tetrachloride) and dispersive solvent (1 mL acetonitrile) were injected into the aqueous samples (5.00 mL) and the cloudy solution was observed. After centrifugation, the enriched analytes in the bottom CCl(4) phase were determined by liquid chromatography with fluorescence detection. Under the optimum conditions, the enrichment factors (EFs) for metoprolol, bisoprolol, and betaxolol were 180, 190, and 182, and the limits of detection (LODs) were 1.8, 1.4, and 1.0 ng L(-1) , respectively. A good linear relationship between the peak area and the concentration of analytes was obtained in the range of 3-150 ng L(-1) . The relative standard deviations (RSDs) for the extraction of 10 ng L(-1) of beta-blockers were in the range of 4.6-5.7% (n = 5). Compared with other methods, dispersive liquid-liquid microextraction is a very simple, rapid, sensitive (low limit of detection), and economical (only 1.06 mL volume of organic solvent) method, which is in compliance with the requirements of green analytical methodologies.

Analysis of β‐blockers in groundwater using large‐volume injection coupled‐column reversed‐phase liquid chromatography with fluorescence detection and liquid chromatography time‐of‐flight mass spectrometry

Atenolol, nadolol, metoprolol, bisoprolol and betaxolol were simultaneously determined in groundwater samples by large-volume injection coupled-column reversed-phase liquid chromatography with fluorescence detection (LVI-LC-LC-FD) and liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS). The LVI-LC-LC-FD method combines analyte isolation, preconcentration and determination into a single step. Significant reductions in costs for sample pre-treatment (solvent and solid phases for clean up) and method development times are also achieved. Using LC-TOF-MS, accurate mass measurements within 3 ppm error were obtained for all of the β-blockers studied. Empirical formula information can be obtained by this method, allowing the unequivocal identification of the target compounds in the samples. To increase the sensitivity, a solid-phase extraction step with Oasis MCX cartridge was carried out yielding recoveries of 79-114% (n=5) with RSD 2-7% for the LC-TOF-MS method. SPE gives a high purification of β-blockers compared with the existing methods. A 100% methanol wash was allowed for these compounds with no loss of analytes. Limit of quantification was 1-7 ng/L for LVI-LC-LC-FD and 0.25-5 ng/L for LC-TOF-MS. As a result of selective extraction and effective removal of coextractives, no matrix effect was observed in LVI-LC-LC-FD and LC-TOF-MS analyses. The methods were applied to detect and quantify β-blockers in groundwater samples of Almería (Spain).

Chiral Separation of Several Pyrethroids on Polysaccharide‐Based Chiral Stationary Phases Under Normal and Reversed Phase Modes

Abstract The enantiomers of eight pyrethroid insecticides have been separated by three polysaccharide‐based chiral stationary phases (CSP), namely Chiralcel OD‐R, Chiralpak AD, and Chiralcel OJ, both in reversed and normal phase modes. Deltamethrin, fenpropathrin, and lambda‐cyhalothrin could be baseline separated on Chiralcel OD‐R in reversed phase mode with R s values of 1.39, 1.29, and 1.17, respectively. However, the best separations for deltamethrin and fenpropathrin and tau‐fluvalinate were achieved when the mobile phase was 15% of ethanol in water. Lambda‐cyhalothrin enantiomers were separated using a mobile phase composed of 30% of acetonitrile:water (30:70 v/v). In normal phase mode, Chiralcel OJ gave better chiral separation for those pyrethroids than that of Chiralpak AD. The chiral separation conditions for eight pyrethroid insecticides have been discussed.

Trace analysis of herbicides in wastewaters by a dispersive liquid–liquid microextraction approach and liquid chromatography with quadrupole linear ion trap mass spectrometry: Evaluation of green parameters

An analytical method for determining phenylureas (monuron, isoproturon, diuron, linuron and neburon) and propanil herbicides in wastewater has been developed and validated, and the most significant parameters were compared with the corresponding ones found in the literature, thus showing the method performance. The method involves pre-concentration by a simple, rapid, sensitive and low environmental toxicity temperature-controlled ionic liquid dispersive liquid-liquid microextraction procedure. The herbicides were identified and determined by liquid chromatography with a hybrid triple quadrupole linear ion trap mass spectrometer. Data acquisition in selected-reaction monitoring mode allowed the simultaneous identification and quantification of the analytes using two transitions. The information dependent acquisition scan was performed to carry out the identification of those analytes whose second transition was present at low intensity, also providing extra confirmation for the other analytes. Limits of quantification were in the range 1.0-5.0 ng/L. Good recoveries (95-103%) were obtained for the extraction of the target analytes in wastewater samples. The methodology developed was applied to analyze effluent wastewater samples from a wastewater treatment plant located in an agricultural zone of Almería (Spain) and the results indicated the presence of diuron at mean concentration levels of 73.5 ng/L.

Enantioseparation of Organophosphonate Derivatives on Amylose Tris(3,5‐Dimethylphenylcarbamate) Chiral Stationary Phase by HPLC

Abstract The enantiomers of fourteen O,O‐dialkyl‐2‐benzyl‐oxycarbonyl‐aminoaryl‐ methyl‐phosphonates are directly separated on tris(3,5‐dimethyl‐phenylcarbamate) amylose chiral stationary phases, known as Chiralcel AD. All of the selected compounds are baseline separated. The influence of the position and properties of substituents in benzene rings, the length and steric hindrance of alkoxyl groups of the phosphonate ester on the chiral separation are discussed. When the substituents are in the para‐position of the benzene ring, the separation factor is in the following order α p‐NO2 ≫ α p‐Cl > α p‐CH3 > α p‐H > α p‐OCH3 . When the same substituent is in a different position of the benzene ring, the order of the separation factor is α p‐Cl > α m‐Cl and α p‐NO2 ≫ α m‐NO2 . The values of the separation factor α of the enantiomers where R 1 substituent is a hydrogen (R 1 = H) are always smaller than those of the enantiomers with p‐Cl substituent, whether R 2 was Me, Et, Pr or i‐Pr. Compounds with different substituent R 2 and R 1 where the substituent is H or p‐Cl, the α values always show an order of αPr > αEt > αMe > α i‐Pr. The chiral discrimination in the amylose tris(3,5‐dimethyl‐phenylcarbamate) was based on π–π interaction and H‐bond interaction.

Influence of the alcoholic modifier on the enantioseparation of organophosphonate derivatives on cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase under normal phase mode.

Abstract The enantiomers of fifteen O,O-dialkyl-2-benzyloxycarbonyl- aminoarylmethyl-phosphonates are directly separated on cellulose tris(3,5-dimethyl-phenylcarbamate) chiral stationary phase using different alcohols as organic mobile phase modifier. The influence of the position and properties of substituents in benzene ring, the length and steric hindrance of alkoxyl groups of the phosphonate ester on the chiral separation were discussed using different alcohol modifiers namely, ethanol, n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol. The study indicates that with the use of different alcohol modifiers in mobile phase, the capacity factor (k) was in the order of k EtOH<k PrOH<k BuOH<k i-PrOH. The results also show that using n-butyl alcohol or isopropyl alcohol as mobile phase modifier achieve better chiral separation for these organophosphonate derivatives than that using ethanol or n-propyl alcohol.

Diseño de un video tutorial para la mejora del aprendizaje de conceptos y procedimientos difíciles en el Área de Química Analítica

The study presented here examines the incorporation of a video tutorial as a supplement to learning in an advanced Instrumental Analytical Chemistry course. The video tutorial was based on “matrix effect” problem and it was designed by the instructor using audio narration from Powerpoint in the “screencast” mode. It was uploaded to the courses Web site portal (Blackboard Learn) at the University of Almería. The video has been shown to serve as a suitable learning that prepares students for laboratory more effectively, with an average of 70% more students answering questions correctly after watching the video than after receiving only teaching assistant instruction.