Search

Two dispersive liquid-liquid microextraction (DLLME) approaches including temperature-controlled ionic liquid dispersive liquid-liquid microextraction (TCIL-DLLME) and ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (US-IL-DLLME) were compared for the extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, lufenuron and flufenoxuron) from wastewater samples prior to their determination by high-performance liquid chromatography with a hybrid triple quadrupole-linear ion trap-mass spectrometer (LC-QqLIT-MS/MS). Influential parameters affecting extraction efficiency were systematically studied and optimized and the most significant green parameters were quantified and compared. The best results were obtained using the US-IL-DLLME procedure, which employed the IL 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and methanol (MeOH) as extraction and disperser solvent, respectively. US-IL-DLLME procedure was fast, easy, low environmental toxicity and, it was also able to successfully extract all selected benzoylureas. This method was extensively validated with satisfactory results: limits of detection and quantification were in the range 0.5-1.0 ng L(-1) and 1.5-3.5 ng L(-1), respectively, whereas recovery rates ranged from 89 to 103% and the relative standard deviations were lower than 13.4%. The applicability of the method was assessed with the analysis of effluent wastewater samples from a wastewater treatment plant located in an agricultural zone of Almería (Spain) and the results indicated the presence of teflubenzuron at mean concentration levels of 11.3 ng L(-1). US-IL-DLLME sample treatment in combination with LC-QqLIT-MS/MS has demonstrated to be a sensitive, selective and efficient method to determine benzoylurea insecticides in wastewaters at ultra-trace levels., (Copyright © 2014 Elsevier B.V. All rights reserved.)

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., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The present paper describes a solid-phase extraction by packed multi-walled carbon nanotubes, followed by liquid chromatography-mass spectrometry, method for the determination of some of the most consumed drugs including four β-blockers and eight non-steroidal anti-inflammatory drugs, in river and wastewater samples. High extraction efficiency was found for most drugs due to the large specific surface area and high adsorption capacity of this nanomaterial compared with other conventional solid-phase extraction sorbents, and matrix effect was present only for two of the twelve studied drugs. Only 20mg of carbon nanotubes was enough to preconcentrate the analytes with recoveries from 68% to 107% for most of them. The pharmaceuticals were analyzed by liquid chromatography coupled to a hybrid triple quadrupole-linear ion trap-mass spectrometer at ultra-trace levels. Data acquisition was carried out in selected reaction monitoring mode, using two transitions for simultaneous identification and quantification of the analytes. Additionally, an information dependent acquisition scan was performed to carry out the identification of those analytes whose second transition was absent or was present at low intensity. The analytical performance of the whole method was evaluated in two environmental water matrices (river and wastewaters). Matrix effect was not found in river water, quantitation being carried out with calibration graphs built with solvent based standard. On the contrary, matrix effect was present in wastewater for some of the target drugs and, therefore, quantitation was carried out using the standard addition method. Limits of detection and quantitation in river waters were in the range of 9-36 and 23-121ngL(-1), respectively and the relative standard deviation of the full method was less than 17%. The proposed methodology was applied to the analysis of three river water and two wastewater (influent and effluent) samples, all of them from Almería (Spain). Some pharmaceuticals were found in river water at concentration levels near to or lower than their quantitation limits, whereas the most consumed pharmaceuticals were found at high concentration levels in influent wastewater and were not detected or were found at lower levels in the effluent wastewater sample., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A simple, rapid, low environmental toxicity and sensitive ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (US-IL-DLLME) procedure was developed for the extraction of nine pharmaceuticals (paracetamol, metoprolol, bisoprolol, betaxolol, ketoprofen, naproxen, ibuprofen, flufenamic acid and tolfenamic acid) in wastewater, and their determination using high-performance liquid chromatography with a hybrid triple quadrupole-linear ion trap-mass spectrometer (LC-QqLIT-MS). The IL 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and acetonitrile (ACN) were used as extraction and disperser solvent, respectively, for the DLLME procedure, instead of using toxic chlorinated solvent. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, type and volume of disperser solvent, cooling in ice-water, sonication time, centrifuging time, sample pH and ionic strength, were optimized. The ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution using a small volume of disperser solvent (0.5mL of acetonitrile), which increased the extraction efficiency and reduced the equilibrium time. A slight increase in the recoveries of pharmaceuticals was observed when an ice-water bath extraction step was included in the analytical procedure. In this way, enrichment factors between 255 and 340 were obtained. Data acquisition in selected reaction monitoring mode (SRM), allowed the simultaneous identification and quantification of the analytes using two transitions (SRM1 and SRM2). Additionally, the information dependent acquisition (IDA) scan was performed to carry out the identification of those analytes whose second transition was absent or was present at low intensity, also providing extra confirmation for the other analytes. The optimized US-IL-DLLME-LC-QqLIT-MS method showed a good precision level, with relative standard deviation values between 1.1% and 11.3%. Limits of detection and quantification were in the range 0.2-60ngL(-1) and 1.0-142ngL(-1), respectively. Good enrichment factors (255-340) and recoveries (88-111%) were obtained for the extraction of the target analytes in wastewater samples. This method has been successfully applied to analyze effluent wastewater samples from a municipal wastewater treatment plant located in Almería (Spain) and the results indicated the presence of flufenamic acid and metoprolol in concentration levels of 0.1 and 1.3μgL(-1), respectively., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Abstract: A simple multidimensional system for direct injection of large volumes has been developed for the determination of five beta-blockers (atenolol, nadolol, metoprolol, bisoprolol and betaxolol) in wastewater using fluorescence detection. A C18 50mm×4.6mm i.d. column coupled to a RP Amide C16 150mm×4.6mm i.d. column for analyte clean-up and determination were used, respectively. The capability of a first column for eliminating large, interfering molecules, combined with an optimised, coupled-column liquid chromatography separation procedure (LC–LC), large volume injection (LVI) and fluorescence detection (FD), gave excellent sensitivity and selectivity for the target analytes. The LVI-LC–LC-FD method combines analyte isolation, preconcentration and determination into a single step. Detection limits obtained in wastewater were lower than, or equal to, 0.0020μgL−1. Limits of quantification (LOQs) obtained in the matrix according to IUPAC, ranged between 0.0052 and 0.0089μgL−1, whereas LOQs calculated according to EURACHEM Guidance, varied between 0.4 and 0.6μgL−1. Accuracy values ranged from 82 to 107% (n =3) and relative standard deviation (RSD) values ranged from 0.8 to 9%. The LVI-LC–LC-FD method was applied for determining the target analytes in wastewater samples obtained in Almería (Spain). [Copyright &y& Elsevier]

Abstract: This overview covers current chemometric methodologies using second-order advantage to solve problems of analyzing highly complex matrices. Among the existing algorithms, it focuses on those most frequently used (e.g., the standard for second-order approaches to data analysis, PARAFAC (parallel factor analysis), and MCR-ALS (multivariate curve resolution alternating least squares), as well as the most recently implemented BLLS (bilinear least-squares), and U-PLS/RBL (unfolded partial least squares/residual bilinearization)). All of these are based on linear models. The overview also covers ANN/RBL (artificial neural networks followed by residual bilinearization), which achieves the second-order advantage in systems involving non-linear behavior. In addition, the overview deals with the drawbacks of these approaches, as well as other drawbacks that are inherent in the analytical techniques to question. [Copyright &y& Elsevier]

Abstract: An analytical method for the simultaneous determination of seven non-steroidal anti-inflammatory drugs (naproxen, ketoprofen, diclofenac, piroxicam, indomethacin, sulindac and diflunisal) and the anticonvulsant carbamazepine in river and wastewater is reported. The method involves pre-concentration and clean-up by solid-phase microextraction using polydimethylsiloxane/divinylbenzene fibers, followed by liquid chromatography with diode array detection analysis. Owing to the fact that river water samples did not contain interferences and no sensitivity changes due to sample matrix were observed, external calibration was implemented. Standardization was also applied in order to carry out the prediction step by preparing only two diluted standards that were subjected to the pre-concentration step and a set of standards prepared in solvent. For the analysis of wastewater samples, in contrast, it was necessary to implement standard addition calibration in combination with the multivariate curve resolution-alternating least squares (MCR-ALS) algorithm, which allowed us to overcome matrix effect and exploit the second order advantage. Recoveries ranging from 72% to 125% for all pharmaceuticals proved the accuracy of the proposed method in river water samples. On the other hand, wastewater sample recoveries ranged from 83% to 140% for all pharmaceuticals, showing an acceptable performance – considering this sample contains no modeled interferences. [Copyright &y& Elsevier]

Abstract: A new powerful algorithm (unfolded-partial least squares followed by residual bilinearization (U-PLS/RBL)) was applied for first time on second-order liquid chromatography with diode array detection (LC–DAD) data and compared with a well-known established method (multivariate curve resolution-alternating least squares (MCR-ALS)) for the simultaneous determination of eight tetracyclines (tetracycline, oxytetracycline, meclocycline, minocycline, metacycline, chlortetracycline, demeclocycline and doxycycline) in wastewaters. Tetracyclines were pre-concentrated using Oasis Max C18 cartridges and then separated on a Thermo Aquasil C18 (150mm×4.6mm, 5μm) column. The whole method was validated using Milli-Q water samples and both univariate and multivariate analytical figures of merit were obtained. Additionally, two data pre-treatment were applied (baseline correction and piecewise direct standardization), which allowed to correct the effect of breakthrough and to reduce the total interferences retained after pre-concentration of wastewaters. The results showed that the eight tetracycline antibiotics can be successfully determined in wastewaters, the drawbacks due to matrix interferences being adequately handled and overcome by using U-PSL/RBL. [Copyright &y& Elsevier]

Abstract: The effect of piecewise direct standardization (PDS) and baseline correction approaches was evaluated in the performance of multivariate curve resolution (MCR-ALS) algorithm for the resolution of three-way data sets from liquid chromatography with diode-array detection (LC-DAD). First, eight tetracyclines (tetracycline, oxytetracycline, chlorotetracycline, demeclocycline, methacycline, doxycycline, meclocycline and minocycline) were isolated from 250mL effluent wastewater samples by solid-phase extraction (SPE) with Oasis MAX 500mg/6mL cartridges and then separated on an Aquasil C18 150mm×4.6mm (5μm particle size) column by LC and detected by DAD. Previous experiments, carried out with Milli-Q water samples, showed a considerable loss of the most polar analytes (minocycline, oxitetracycline and tetracycline) due to breakthrough. PDS was applied to overcome this important drawback. Conversion of chromatograms obtained from standards prepared in solvent was performed obtaining a high correlation with those corresponding to the real situation (r 2 =0.98). Although the enrichment and clean-up steps were carefully optimized, the sample matrix caused a large baseline drift, and also additive interferences were present at the retention times of the analytes. These problems were solved with the baseline correction method proposed by Eilers. MCR-ALS was applied to the corrected and uncorrected three-way data sets to obtain spectral and chromatographic profiles of each tetracycline, as well as those corresponding to the co-eluting interferences. The complexity of the calibration model built from uncorrected data sets was higher, as expected, and the quality of the spectral and chromatographic profiles was worse. [Copyright &y& Elsevier]