Ana Uclés

Determination of pesticide residues in high oil vegetal commodities by using various multi-residue methods and clean-ups followed by liquid chromatography tandem mass spectrometry.

Several extraction methods were evaluated in terms of recoveries and extraction precision for 113 pesticides in avocado: QuEChERS with various d-SPE clean-ups (Z-Sep, Z-Sep+, PSA+C18 and silica), miniLuke and ethyl acetate. Extracts were analysed using liquid chromatography coupled with triple quadrupole mass spectrometer working in multi-reaction monitoring mode. Z-Sep and Z-Sep+ are new types of material for high lipid matrices - these two sorbents contain ZrO2, which improves fat removal from the extracts. The QuEChERS protocol with Z-Sep provided the highest number of pesticides with recoveries in the 70-120% range along with the lowest amount of coextracted matrix compounds. Subsequently, this method was validated in two matrices - avocado and almonds. In the validation recoveries at two levels - 10 and 50μg/kg - limit of quantitation, linearity, matrix effects, as well as the inter- and intraday precision were studied. In the avocado samples, 107 analytes had LOQs equal to 10μg/kg (signal to noise of quantitative transition was equal 20 or more). In the almond samples, 92 pesticides had LOQs equal to 10μg/kg (S/N≥20) and 2 pesticides at 50μg/kg. The validated method was employed in the analysis of real avocado and almond samples.

Pesticide analysis in teas and chamomile by liquid chromatography and gas chromatography tandem mass spectrometry using a modified QuEChERS method: Validation and pilot survey in real samples

This paper presents the validation of a modified QuEChERS method in four matrices - green tea, red tea, black tea and chamomile. The experiments were carried out using blank samples spiked with a solution of 86 pesticides (insecticides, fungicides and herbicides) at four levels - 10, 25, 50 and 100 μg/kg. The samples were extracted according to the citrate QuEChERS protocol; however, to reduce the amount of coextracted matrix compounds, calcium chloride was employed instead of magnesium sulphate in the clean-up step. The samples were analysed by LC-MS/MS and GC-MS/MS. Included in the scope of validation were: recovery, linearity, matrix effects, limits of detection and quantitation as well as intra-day and inter-day precision. The validated method was used in a real sample survey carried out on 75 samples purchased in ten different countries. In all matrices, recoveries of the majority of compounds were in the 70-120% range and were characterised by precision lower than 20%. In 85% of pesticide/matrix combinations the analytes can be detected quantitatively by the proposed method at the European Union Maximum Residue Level. The analysis of the real samples revealed that large number of teas and chamomiles sold in the European Union contain pesticides whose usage is not approved and also pesticides in concentrations above the EU MRLs.

Determination of malachite green residues in fish using molecularly imprinted solid-phase extraction followed by liquid chromatography-linear ion trap mass spectrometry.

This paper describes the development of an analytical procedure to determine malachite green (MG) residues in salmon samples using molecularly imprinted polymers (MIPs) as the extraction and clean-up material, followed by liquid chromatography-linear ion trap mass spectrometry (LC-QqQLIT-MS/MS). MG and two structurally related compounds, crystal violet (CV) and brilliant green (BG) were employed for the selectivity test. The imprinted polymers exhibited high binding affinity for MG, while CV and BG showed less binding capacity: 47% and 34%, respectively. The recovery values of MG in salmon samples fortified with leucomalachite green (LMG) were determined by measuring the amount of MG in the sample, after carrying out the oxidation reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), which converts the LMG back into chromic-form. The average recovery of MG in spiked salmon muscle over the concentration range 1-100 ng g(-1) was 98% with a relative standard deviation value (R.S.D.) below 12%. The method detection limits (MDLs) obtained for MG, CV, BG and their leuco-metabolites were in the range of 3-20 ng kg(-1) (ppt).

Ultrasound-assisted ionic liquid dispersive liquid–liquid microextraction coupled with liquid chromatography-quadrupole-linear ion trap-mass spectrometry for simultaneous analysis of pharmaceuticals in wastewaters

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.

Analytical improvements of hybrid LC-MS/MS techniques for the efficient evaluation of emerging contaminants in river waters: a case study of the Henares River (Madrid, Spain)

PurposeInstrumental capabilities and software tools of modern hybrid mass spectrometry (MS) instruments such as high-resolution mass spectrometry (HRMS), quadrupole time-of-flight (QTOF), and quadrupole linear ion trap (QLIT) were experimentally investigated for the study of emerging contaminants in Henares River water samples.MethodsAutomated screening and confirmatory capabilities of QTOF working in full-scan MS and tandem MS (MS/MS) were explored when dealing with real samples. Investigations on the effect of sensitivity and resolution power influence on mass accuracy were studied for the correct assignment of the amoxicillin transformation product 5(R) amoxicillin-diketopiperazine-2′,5′ as an example of a nontarget compound. On the other hand, a comparison of quantitative and qualitative strategies based on direct injection analysis and off-line solid-phase extraction sample treatment were assayed using two different QLIT instruments for a selected group of emerging contaminants when operating in selected reaction monitoring (SRM) and information-dependent acquisition (IDA) modes.Results and discussionSoftware-aided screening usually needs a further confirmatory step. Resolving power and MS/MS feature of QTOF showed to confirm/reject most findings in river water, although sensitivity-related limitations are usually found. Superior sensitivity of modern QLIT-MS/MS offered the possibility of direct injection analysis for proper quantitative study of a variety of contaminants, while it simultaneously reduced the matrix effect and increased the reliability of the results. Confirmation of ethylamphetamine, which lacks on a second SRM transition, was accomplished by using the IDA feature.ConclusionHybrid MS instruments equipped with high resolution and high sensitivity contributes to enlarge the scope of targeted analytes in river waters. However, in the tested instruments, there is a margin of improvement principally in required sensitivity and data treatment software tools devoted to reliable confirmation and improved automated data processing.

Application of zirconium dioxide nanoparticle sorbent for the clean-up step in post-harvest pesticide residue analysis

The use of yttria-stabilized zirconium dioxide nanoparticles as d-SPE clean-up sorbent for a rapid and sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the determination of post-harvest fungicides (carbaryl, carbendazim, chlorpropham, diphenylamine, ethoxyquin, flutriafol, imazalil, iprodione, methomyl, myclobutanil, pirimiphos-methyl, prochloraz, pyrimethanil, thiabendazole, thiophanate-methyl and tolclofos-methyl) in orange and pear samples has been evaluated and validated. The sample preparation was a modification of the QuEChERS extraction method using yttria-stabilized zirconium dioxide and multi-walled carbon nanotubes (MWCNTs) nanoparticles as the solid phase extraction (d-SPE) clean-up sorbents prior to injecting the ten-fold diluted extracts into the LC system. By using the yttria-stabilized zirconium dioxide extraction method, more recoveries in the 70-120% range were obtained - thus this method was used for the validation. Quantification was carried out using a matrix-matched calibration curve which was linear in the 1-500 µg kg(-1) range for almost all the pesticides studied. The validated limit of quantification was 10 µg kg(-1) for most of the studied compounds, except chlorpropham, ethoxyquin and thiophanate-methyl. Pesticide recoveries at the 10 and 100 µg kg(-1) concentration levels were satisfactory, with values between 77% and 120% and relative standard deviations (RSD) lower than 10% (n=5). The developed method was applied for the determination of selected fungicides in 20 real orange and pear samples. Four different pesticide residues were detected in 10 of these commodities; 20% of the samples contained pesticide residues at a quantifiable level (equal to or above the LOQs) for at least one pesticide residue. The most frequently-detected pesticide residues were: carbendazim, thiabendazole and imazalil-all were below the MRL. The highest concentration found was imazalil at 1175 µg kg(-1) in a pear sample.

Validation and application of micro flow liquid chromatography–tandem mass spectrometry for the determination of pesticide residues in fruit jams

In this study, a very sensitive method was validated to determine pesticides residues in fruit jams using micro flow liquid chromatography-tandem mass spectrometry (µLC-MS/MS). A slurry of the fruit jams and water was prepared to yield homogeneous samples. Because of the high sensitivity achieved with the µLC-MS/MS equipment and to minimize matrix effects, the QuEChERS extracts were diluted 30-fold before the analysis. The validation was performed analyzing spiked samples at 9 and 45 µg kg(-1) (n=5). The method met validation criteria of 70-120% recovery and RSD≤20% for 92% of the 107 pesticides evaluated. The reporting limit (RL) was 9 and 45 µg kg(-1) for respectively 66% and 26% of the analytes, 5% of the compounds did not fulfill the requirements for validation and 3% were not detected at the studied concentrations. The validated method was applied to the analysis of 51 different fruit jam samples from Brazil and Spain and pesticide residues were detected in 41 samples, 26 of which contained at least one pesticide at concentration >10 µg kg(-1).

Chemical and Ecotoxicological Assessment of Dendrimers in the Aquatic Environment

Dendrimers represent a class of polymers with promising applications as nanodevices in biomedicine and industry. This review provides a comprehensive summary of recent progress in their chemical characterization and toxicological assessment. Research into different toxicological and ecotoxicological approaches reveals correlations with a profile of hemolytic toxicity, cytotoxicity and hematological toxicity. This chapter provides a brief but complete synopsis of assays majorly applied such as cell viability assays and in vivo studies with aquatic species. The characterization techniques usually involved in dendrimers analysis were: scattering, microscopy, spectroscopy or spectrometry, and proved to be useful for effective evaluation of synthesis processes. In other relevant fields such as bioanalysis and toxicology, application of advanced mass spectrometry techniques can contribute providing enhanced characterization and quantification at trace levels. The last part is dedicated to present a new approach to characterize and quantify PAMAM dendrimers by liquid chromatography–mass spectrometry-based methods using LC-ESI-TOF-MS and LC-ESI-QTOF-MS systems.

Shifting the paradigm in gas chromatography mass spectrometry pesticide analysis using high resolution accurate mass spectrometry

In the last 10 years, the majority of the pesticide food control laboratories moved from GC-MS to GC-MS/MS as the preferred analytical technique to address GC amenable compounds. The main reason for this change was the negative impact on the single stage GC-MS analysis caused by the interference from coeluting matrix compounds. The new development of gas chromatography coupled to high resolution accurate mass spectrometry (GC-HRAMS) provides opportunities to overcome such matrix interferences as a result of its much higher selectivity; allowing laboratories to carry out full-scan analysis covering the most exigent analytical performance criteria. The aim of this work is the evaluation of the main analytical performance parameters for the multiresidue screening of pesticide residues by a gas chromatography-Orbitrap™ mass spectrometer in fruits and vegetables. Electron ionization and full-scan high resolution mass spectrometry was selected for this evaluation. Mass resolving power, selectivity, sensitivity, analyte identification and database generation are discussed in light of the analysis of various commodities and a large scope of pesticides. The selected operational conditions provided optimal mass accuracy, within ±1mDa and achieved LOQs of 10μg/kg or lower for practically all the selected pesticides and commodities. Applicability for quantitative residue analysis was verified by the validation of the 210 pesticides in four matrices (tomato, apple, leek and orange). The performance of the GC-EI-full scan Orbitrap HRAMS developed method was confirmed with the analysis of 102 real samples providing good results.

Benzimidazole and imidazole fungicide analysis in grape and wine samples using a competitive enzyme-linked immunosorbent assay

This manuscript reports a quantitative pesticide residue method analysis employing an enzyme-linked immunosorbent assay (ELISA) for detecting carbendazim, imazalil and thiabendazole pesticide residues in vegetable samples. The results have been compared with those obtained from a liquid chromatography system coupled to a triple quadrupole mass spectrometer (LC-ESI-QqQ-MS). A validation study was undertaken to establish this methods performance characteristics on the 3 pesticide residues in two commodities (table grapes and wine). The carbendazim, imazalil and thiabendazole ELISA showed an IC50 reporting limit ranging from 0.5 to 13.8 µg kg−1. The limit of quantification of the developed assay was 5 µg kg−1 for both grape and wine matrices. The optimised assay was compared with a reference procedure based on liquid chromatography using samples acquired from various supermarkets, and a good correlation between both methods was found.