Bienvenida Gilbert-López

Sample treatment and determination of pesticide residues in fatty vegetable matrices: A review

A demanding task in pesticide residue analysis is yet the development of multi-residue methods for the determination of pesticides in vegetables with relatively high fat content (i.e. edible oils and fatty vegetables). The separation of pesticides and other chemical contaminants from high-fat food samples prior to subsequent steps in the analytical process is yet a challenging issue to which much effort in method development has being applied. This review addresses the main sample treatment methodologies for pesticide residue analysis in fatty vegetable matrices. Even with the advent of advanced hyphenated techniques based on mass spectrometry these complex fatty matrices usually require extensive sample extraction and purification. Current methods involve the use of one or the combination of some of the following techniques for both the sample extraction and clean-up steps: liquid-liquid partitioning, solid-phase extraction (SPE), gel-permeation chromatography (GPC), matrix solid-phase dispersion (MSPD), etc. An overview of methods developed for these contaminants in fatty vegetables matrices is presented. Sample extraction and purification techniques are discussed and their most recent applications are highlighted. This review emphasizes that sample preparation is a critical step, but also the determination method is, and cannot be treated separately from sample treatment. In recent years, the appearance and use of new, more polar pesticides has fostered the development of liquid chromatography/mass spectrometry (LC-MS) besides gas chromatography. The main features of LC-MS for the analysis of multi-class pesticides in fatty vegetable samples will be also underlined, with an emphasis on the multi-class, multi-residue strategy and the difficulties associated.

Determination of Pesticide Residues in Fruit-Based Soft Drinks

Here we report the first worldwide reconnaissance study of the presence and occurrence of pesticides in fruit-based soft drinks. While there are strict regulations and exhaustive controls for pesticides in fruits, vegetables, and drinking water, scarce attention has been paid to highly consumed derivate products, which may contain these commodities as ingredients. In the case of the fruit-based soft drinks industry, there are no clear regulations, relating to pesticides, which address them, even when there is significant consumption in vulnerable groups such as children. In this work, we have developed a screening method to search automatically for up to 100 pesticides in fruit-based soft drinks extracts based on the application of liquid chromatography-electrospray time-of-flight mass spectrometry (LC-TOF MS). The sample extracts injected were obtained by a preliminary sample treatment step based on solid-phase extraction using hydrophilic-lipophilic balanced polymer-based reverse phase cartridges and methanol as eluting solvent. Subsequent identification, confirmation, and quantitation were carried out by LC-TOF MS analysis: the confirmation of the target species was based on retention time matching and accurate mass measurements of protonated molecules ([M + H]+) and fragment ions (obtaining accuracy errors typically lower than 2 ppm). With the proposed method, we measured over 100 fruit-based soft drink samples, purchased from 15 different countries from companies with brands distributed worldwide and found relatively large concentration levels of pesticides in most of the samples analyzed. The concentration levels detected were of the micrograms per liter level, low when considering the European maximum residue levels (MRLs) set for fruits but very high (i.e., 300 times) when considering the MRLs for drinking or bottled water. The detected pesticides (carbendazim, thiabendazole, imazalil and its main degradate, prochloraz and its main degradate, malathion, and iprodione) are mainly those applied to crops in the final stages of production (postharvest treatment), some of them contain chlorine atoms in their structures. Therefore, steps should be taken with the aim of removing any traces of pesticides in these products, in order to avoid this source of pesticide exposure on the consumer, particularly on vulnerable groups with higher exposure, such as children.

Large-scale pesticide testing in olives by liquid chromatography-electrospray tandem mass spectrometry using two sample preparation methods based on matrix solid-phase dispersion and QuEChERS.

In this work we have evaluated the performance of two sample preparation methodologies for the large-scale multiresidue analysis of pesticides in olives using liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS). The tested sample treatment methodologies were: (1) liquid-liquid partitioning with acetonitrile followed by dispersive solid-phase extraction clean-up using GCB, PSA and C18 sorbents (QuEChERS method - modified for fatty vegetables) and (2) matrix solid-phase dispersion (MSPD) using aminopropyl as sorbent material and a final clean-up performed in the elution step using Florisil. An LC-MS/MS method covering 104 multiclass pesticides was developed to examine the performance of these two protocols. The separation of the compounds from the olive extracts was achieved using a short C18 column (50 mm x 4.6 mm i.d.) with 1.8 microm particle size. The identification and confirmation of the compounds was based on retention time matching along with the presence (and ratio) of two typical MRM transitions. Limits of detection obtained were lower than 10 microgkg(-1) for 89% analytes using both sample treatment protocols. Recoveries studies performed on olives samples spiked at two concentration levels (10 and 100 microgkg(-1)) yielded average recoveries in the range 70-120% for most analytes when QuEChERS procedure is employed. When MSPD was the choice for sample extraction, recoveries obtained were in the range 50-70% for most of target compounds. The proposed methods were successfully applied to the analysis of real olives samples, revealing the presence of some of the target species in the microgkg(-1) range. Besides the evaluation of the sample preparation approaches, we also discuss the use of advanced software features associated to MRM method development that overcome several limitations and drawbacks associated to MS/MS methods (time segments boundaries, tedious method development/manual scheduling and acquisition limitations). This software feature recently offered by different vendors is based on an algorithm that associates retention time data for each individual MS/MS transition, so that the number of simultaneously traced transitions throughout the entire chromatographic run (dwell times and sensitivity) is maximized.

Multiclass detection and quantitation of antibiotics and veterinary drugs in shrimps by fast liquid chromatography time-of-flight mass spectrometry

A fast liquid chromatography time-of-flight mass spectrometry (LC-TOFMS) method has been developed for simultaneous quantitative multiclass determination of residues of selected antibiotics and other veterinary drugs (benzalkonium chloride, ethoxyquin, leucomalachite green (LMG), malachite green (MG), mebendazole, sulfadiazine, sulfadimethoxine, sulfamethazine, sulfamethizole, sulfanilamide, sulfapyridine, sulfathiazole and trimethoprim) in shrimps. Different sample treatment methodologies were tested for the extraction of the targeted species based on either liquid partitioning with different solvents, solid-phase extraction or and matrix solid-phase dispersion. The final selected extraction method consisted of solid-liquid extraction protocol using acetonitrile as solvent followed by a clean-up step with primary secondary amine (QuEChERS). Recovery rates for the extraction of the selected multiclass chemicals were in the range 58-133%. Subsequent identification, confirmation and quantitation were carried out by LC-TOFMS analysis using a reverse-phase C(18) column with 1.8 μm particle size. The confirmation of the target species was based on accurate mass measurements of the protonated molecules ([M+H](+)) and their fragment ions, obtaining routine accuracy errors lower than 2 ppm in most cases. The optimized LC-TOFMS method displayed excellent sensitivity for the studied analytes, with limits of detection (LODs) in the range 0.06-7 μg kg(-1). Finally, the proposed method was successfully applied to the analysis of 12 shrimp samples collected from different supermarkets, showing the potential applicability of the method for ultratrace detection of these chemicals in such complex matrix.

Monitoring of selected priority and emerging contaminants in the Guadalquivir River and other related surface waters in the province of Jaén, South East Spain

The province of Jaén counts with four natural parks, numerous rivers, reservoirs and wetlands; moreover, it is probably the region with higher olive oil production in the world, which makes this zone a proper target to be studied based on the European Water Framework Directive 2000/60/CE. The aim of this survey is to monitor a total number of 373 compounds belonging to different families (pesticides, PAHs, nitrosamines, drugs of abuse, pharmaceuticals and life-style compounds) in surface waters located at different points of the province of Jaén. Among these compounds some priority organic substances (regulated by the EU Directive 2008/105/EC) and pollutants of emerging concern (not regulated yet) can be found. A liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOFMS) method covering 340 compounds was developed and applied, together with a gas chromatography triple-quadrupole mass spectrometry (GC-MS/MS) method which enabled the analysis of 63 organic contaminants (30 of these compounds are analyzed by LC-TOFMS as well). From April 2009 to November 2010 a total of 83 surface water samples were collected (rivers, reservoirs and wetlands). In this period numerous organic contaminants were detected, most of them at the ng L(-1) level. The most frequently priority substances found were chlorpyrifos ethyl, diuron and hexachlorobenzene. Within the other groups, the most frequently detected compounds were: terbuthylazine, oxyfluorfen, desethyl terbuthylazine, diphenylamine (pesticide family); fluorene, phenanthrene, pyrene (PAHs group), codeine, paracetamol (pharmaceuticals compounds) and caffeine, nicotine (life-style compounds). As is could be expected, the total concentration of emerging contaminants is distinctly larger than that of priority pollutants, highlighting the importance of continuing with the study of their presence, fate and effects in aquatic environments. However, concentration levels (at the ng per liter level) are low in general for both kinds of contaminants which minimizes the possible harmful effect on the environment.

Evaluation of two sample treatment methodologies for large-scale pesticide residue analysis in olive oil by fast liquid chromatography-electrospray mass spectrometry.

In this study, a comprehensive evaluation of two simple sample treatment methodologies has been carried out for the development of large-scale multi-residue methods for pesticide testing in olive oil. The proposed methodologies are based on (a) liquid-liquid partitioning with acetonitrile followed by dispersive solid-phase extraction clean-up using graphitized carbon black, primary-secondary amine and C(18) sorbents; (b) liquid partitioning with acetonitrile saturated with petroleum ether followed by matrix solid-phase dispersion (MSPD) using aminopropyl as sorbent material and a Florisil cartridge for final clean-up in the elution step. To evaluate the proposed sample treatment methodologies, 105 representative multi-class pesticides were studied using fast liquid chromatography-electrospray time-of-flight mass spectrometry (LC-TOFMS). For validation purposes, recoveries studies were carried out at 10 and 100microgkg(-1) levels, yielding recovery rates in the range 70-130% for 72% of analytes using liquid-liquid procedure and for 57% analytes using MSPD procedure. The LC-MS method provided good linearity, precision and accuracy. The limits of detection obtained were lower than 10microgkg(-1) for more than 85% analytes using both sample treatment methodologies. In addition, minor matrix effects (i.e. signal suppression or enhancement < or =20%) were observed in ca. 70% of the studied compounds. Data obtained shows that both sample treatment methodologies proposed can be successfully applied for large-scale pesticide testing in olive oil samples, showing the ability to quickly detect trace amount of over one hundred target species with different physicochemical properties, without requiring expensive instrumentation for sample treatment step and involving relatively low amounts of solvent consumption and waste generation.

Multi-residue method for the determination of over 400 priority and emerging pollutants in water and wastewater by solid-phase extraction and liquid chromatography-time-of-flight mass spectrometry

This article describes the development and validation of a liquid chromatography high-resolution mass spectrometry method for the simultaneous determination of over 400 multi-class priority and emerging pollutants with different physicochemical properties in environmental waters (surface water and wastewater). The proposed approach is based on the use of a database consisting of retention time/exact mass (of selected ions) pairs implemented with specific software for data analysis. The targeted list comprises 430 contaminants belonging to different compound categories, including 105 multiclass pharmaceuticals (analgesics/anti-inflammatories, antibiotics, lipid regulators, β-blockers, antiepileptic/psychiatrics ulcer healings, diuretics, hormones and bronchodilatadors), life-style products (caffeine, nicotine), 21 drugs of abuse and their metabolites, 279 pesticides and some of their more relevant metabolites, nitrosamines, flame retardants, plasticizers and perfluorinated compounds. The proposed approach included a simple offline solid phase extraction (SPE) step using polymeric cartridges (Oasis HLB) with 200mL of water sample loaded, followed by analysis by rapid resolution liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOFMS) in both positive and negative modes. The identification of the positive findings is accomplished with the data from accurate masses of the target ions along with retention time data and characteristic in-source fragment ions. The overall method performance was satisfactory with limits of quantification lower than 10ngL(-1) for the 44% of studied compounds. Recoveries between 50% and 130% were obtained for the 65% of the analytes (281 compounds). Matrix effects occurring with wastewater matrices were also assessed. The developed method was applied to the determination of target analytes in real surface water and wastewater samples.

Multi-residue determination of pesticides in fruit-based soft drinks by fast liquid chromatography time-of-flight mass spectrometry.

This work reports a rapid and reliable method for the determination of 33 multi-class pesticides in fruit-based soft drinks. The proposed method consists of a sample treatment step based on solid-phase extraction using hydrophilic-lipophilic balanced polymer-based reverse-phase SPE cartridges, followed by identification and quantitation of the target pesticides by rapid resolution liquid chromatography using a short C(18) column (4.6mm x 50mm) with 1.8microm particle size and mass spectrometric detection using electrospray time-of-flight mass spectrometry (LC-TOFMS). The identification and confirmation of the compounds were based on retention time matching along with the accurate mass measurements of the protonated molecules ([M+H](+)) and their main fragment ions. Fruit-based soft drinks spiked at different fortification levels (10 and 50microgL(-1)) yielded average recoveries in the range 66-124% with RSD (%) below 14% (n=6). The obtained limits of quantitation varied in the range 0.02-2microgL(-1). The proposed method was successfully applied to the analysis of 14 market-purchased fruit-based soft drinks samples collected in some European countries, showing its potential applicability and revealing the presence of some of the target species in the microgL(-1) range.

Ambient diode laser desorption dielectric barrier discharge ionization mass spectrometry of nonvolatile chemicals.

In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface.

Downstream processing of Isochrysis galbana: a step towards microalgal biorefinery

An algae-based biorefinery relies on the efficient use of algae biomass through its fractionation of several valuable/bioactive compounds that can be used in industry. If this biorefinery includes green platforms as downstream processing technologies able to fulfill the requirements of green chemistry, it will end-up with sustainable processes. In the present study, a downstream processing platform has been developed to extract bioactive compounds from the microalga Isochrysis galbana using various pressurized green solvents. Extractions were performed in four sequential steps using (1) supercritical CO2 (ScCO2), (2) ScCO2/ethanol (Gas Expanded Liquid, GXL), (3) pure ethanol, and (4) pure water as solvents, respectively. The residue of the extraction step was used as the raw material for the next extraction. Optimization of the ScCO2 extraction was performed by factorial design in order to maximize carotenoid extraction. During the second step, different percentages of ethanol were evaluated (15%, 45% and 75%) in order to maximize the extraction yield of fucoxanthin, the main carotenoid present in this alga; the extraction of polar lipids was also an aim. The third and fourth steps were performed with the objective of recovering fractions with high antioxidant activity, eventually rich in carbohydrates and proteins. The green downstream platform developed in this study produced different extracts with potential for application in the food, pharmaceutical and cosmetic industries. Therefore, a good approach for complete revalorization of the microalgae biomass is proposed, by using processes complying with the green chemistry principles.