Determination of 255 pesticides in edible vegetable oils using QuEChERS method and gas chromatography tandem mass spectrometry

A Critical Review of Analytical Methods for the Quantification of Phthalates Esters in Two Important European Food Products: Olive Oil and Wine

Phthalic acid esters (PAEs) are a class of chemicals widely used as plasticizers. These compounds, considered toxic, do not bond to the polymeric matrix of plastic and can, therefore, migrate into the surrounding environment, posing a risk to human health. The primary source of human exposure is food, which can become contaminated during cultivation, production, and packaging. Therefore, it is imperative to control and regulate this exposure. This review covers the analytical methods used for their determination in two economically significant products: olive oil and wine. Additionally, it provides a summary and analysis of information regarding the characteristics, toxicity, effects on human health, and current regulations pertaining to PAEs in food. Various approaches for the extraction, purification, and quantification of these analytes are highlighted. Solvent and sorbent-based extraction techniques are reviewed, as are the chromatographic separation and other methods currently applied in the analysis of PAEs in wines and olive oils. The analysis of these contaminants is challenging due to the complexities of the matrices and the widespread presence of PAEs in analytical laboratories, demanding the implementation of appropriate strategies.

A lateral flow immunoassay method for the rapid detection of acetochlor and alachlor in vegetable oil by sensitivity enhancement by using dimethyl-β-cyclodextrin

Acetochlor is an endocrine disruptor. The acetochlor residue is strongly lipophilic and can be enriched into products during the manufacturing process. In this study, we found that dimethyl-β-cyclodextrin (DM-β-CD) solution could decrease the apparent oil/water partition coefficient (Koil-w) of acetochlor and increase the sensitivity of fluorescence lateral flow immunoassay (LFIA) for acetochlor simultaneously. Based on this, a simple LFIA method for the determination of acetochlor and alachlor residues in vegetable oil was established. The detection process only involves vortex mixing of an oil sample and dimethyl-β-cyclodextrin solution in a 1 : 3 (V/V) ratio, loading the water phase onto the immunoassay strips and reading the results. Under optimized conditions, the LOD for acetochlor in oil was 3.53 ng g-1, and the working range was 12.03-2000.00 ng g-1. The recoveries of spiked samples ranged from 91.69% ± 1.12% to 112.23% ± 2.20%. Meanwhile, the cross reactivity for alachlor was 108.22%, while for other investigated acetochlor analogues it was less than 1%, and the recoveries of alachlor were from 92.90% ± 8.03% to 113.53% ± 3.40%, which indicate that this method can detect acetochlor and alachlor simultaneously. Compared with the traditional detection method, the pre-treatment process of the proposed method is "green" and simple, and can be applied to the on-site rapid detection of acetochlor and alachlor in vegetable oil and can provide inspiration for the detection of other lipophilic pollutants.

Ultra-high performance liquid chromatography and gas chromatography coupled to tandem mass spectrometry for the analysis of 32 pyrethroid pesticides in fruits and vegetables: A comparative study

In this study, multi-residue analysis methods for 32 pyrethroids in fruit and vegetable samples were established in both GC-MS/MS and UHPLC-MS/MS. The parameters that affecting the ionization efficiencies of pyrethroids in UHPLC-ESI-MS/MS, including ion source temperature, in-source fragmentation, and mobile phase conditions were thoroughly investigated to guarantee better performance. These two techniques were comprehensively compared in terms of recovery, LOQ, linearity, and matrix effects. In general, UHPLC-MS/MS was found suitable for more pesticides than GC-MS/MS. Lower LOQs were obtained for most of the selected pyrethroids in UHPLC-MS/MS. Similar results were obtained in terms of recoveries and RSDs for the validated pesticides in fortification experiments. A total of 136 real samples were analyzed by both techniques, obtaining similar results. The results suggest that UHPLC-MS/MS offers a suitable alternative to GC-MS/MS in the routine analysis of pyrethroids in fruits and vegetables.

Organochlorine pesticides in vegetable oils: An overview of occurrence, toxicity, and chromatographic determination in the past twenty-two years (2000-2022)

Organochlorine pesticides (OCPs) are used globally to control pests in the food industry. However, some have been banned due to their toxicity. Although they have been banned, OCPs are still discharged into the environment and persist for long periods of time. Therefore, this review focused on the occurrence, toxicity, and chromatographic determination of OCPs in vegetable oils over the last 22 years (2000-2022) (111 references).Literature search shows that OCPs kill pests by destroying endocrine, teratogenic, neuroendocrine, immune, and reproductive systems. However, only five studies investigated the fate of OCPs in vegetable oils and the outcome revealed that some of the steps involved during oil processing introduce more OCPs. Moreover, direct chromatographic determination of OCPs was mostly performed using online LC-GC methods fitted with oven transfer adsorption desorption interface. While indirect chromatographic determination was favored by QuEChERS extraction technique, gas chromatography frequently coupled to electron capture detection (ECD), gas chromatography in selective ion monitoring mode (SIM), and gas chromatography tandem mass spectrometry (GC-MS/MS) were the most common techniques used for detection. However, the greatest challenge still faced by analytical chemists is to obtain clean extracts with acceptable extraction recoveries (70-120%). Hence, more research is still required to develop greener and selective extraction methods toward OCPs, thus improving extraction recoveries. Moreover, advanced techniques like gas chromatography high resolution mass spectrometry (GC-HRMS) must also be explored. OCPs prevalence in vegetable oils varied greatly in various countries, and concentrations of up to 1500 µg/kg were reported. Additionally, the percentage of positive samples ranged from 1.1 to 97.5% for endosulfan sulfate.

Development and validation of a modified QuEChERS method for extracting polychlorinated biphenyls and organochlorine pesticides from marine mammal blubber

The monitoring of legacy persistent organic pollutants (POPs) in blubber of key sentinel marine mammal species has been conducted using established techniques for decades. Although these methods for polychlorinated biphenyl (PCB) and organochlorine (OC) pesticide determination provide accurate and reproducible results, they possess some drawbacks in terms of cost, time, and a need for large volumes of toxic solvents. QuEChERS (quick, easy, cheap, effective, rugged, and safe) extractions may help address these issues, but have not been applied to marine mammal blubber/adipose. As such, our aim was to develop, validate, and apply a QuEChERS method for the extraction of PCB and OC contaminants in marine mammal blubber. First, we tested multiple solid-phase extraction and clean-up steps to find the approach that provided the cleanest extracts along with consistent and acceptable analyte recovery, accuracy, and precision. QuEChERS extractions followed by two enhanced matrix removal-lipid (EMR-lipid), one primary-secondary amine (PSA), and one silica gel clean-up showed the highest matrix removal and acceptable recoveries of spiked internal (62-97%) and external standards (61-94%). Solvent usage was reduced by ∼393% and extraction time was reduced by ∼25% (from 16 to 12 h). Next, the method was validated using standard reference material (SRM) NIST 1945. Recovery experiments on SRM (n = 5) showed acceptable recovery for 76% and 77% of PCBs and OC pesticides, respectively, and high precision for 73% and 69% of PCBs and OCs, respectively. Finally, the method was used on a set of southeast Greenland killer whales (n = 13), with previously published PCB and OC data. Bland-Altman plots indicated good agreement between QuEChERS and current-use methods for ΣPCBs and some OCs with no significant constant or proportional bias. These results demonstrate that this QuEChERS extraction method represents an effective, lower cost alternative to current-use extractions for PCBs and OCs in blubber, and likely other high-lipid samples.

A simple and rapid homogeneous fluorescence polarization immunoassay for rapid identification of gutter cooking oil by detecting capsaicinoids

In order to address the widespread concerns with food safety such as adulteration and forgery in the edible oil field, this study developed a fluorescence polarization immunoassay (FPIA) based on a monoclonal antibody in a homogeneous solution system for determination of capsaicinoids in gutter cooking oil by using chemically stable capsaicinoids as an adulteration marker. The prepared fluoresceinthiocarbamyl ethylenediamine (EDF) was coupled with capsaicinoid hapten C, and the synthesized tracer was purified by thin-layer chromatography (TLC) and showed good binding to the monoclonal antibody CPC Ab-D8. The effects of concentration of tracer and recognition components, type and pH of buffer and incubation time on the performance of FPIA were studied. The linear range (IC₂₀ to IC₈₀) was 3.97-97.99 ng/mL, and the half maximal inhibitory concentration (IC₅₀) was 19.73 ng/mL, and the limit of detection (LOD) was 1.56 ng/mL. The recovery rates of corn germ oil, soybean oil and peanut blend oil were in the range of 94.7-132.3%. The experimental results showed that the fluorescence polarization detection system could realize the rapid detection of capsaicinoids, and had the potential to realize on-site identification of gutter cooking oil. As a universal monoclonal antibody, CPC Ab-D8 can also specifically identify capsaicin and dihydrocapsaicin, so the proposed method can be used to quickly monitor for the presence of gutter cooking oil in normal cooking oil.

Development, validation and evaluation of matrix effect of a QuEChERS-based multiresidue method with low temperature dispersive clean-up for analysis of 104 pesticides in cumin (Cuminum cyminum) by LC-MS/MS

BACKGROUND

Until now, there is no method available for analysis of pesticide residues in complex matrices like spices. Therefore, there is an urgent need to develop and validate a QuEChERS-based method for the estimation of 104 pesticides in cumin seed.

RESULTS

Samples were spiked for 109 pesticides at concentrations of 0.1, 0.5 and 1.0 mg kg^-1 . Of these 104 pesticides were recovered. At 0.1, 0.5 and 0.1 mg kg^-1 , recoveries ranged from 71% to 108% when compared with matrix matched standards. Seventeen pesticides showed higher or lower recoveries than acceptable range (70-120%) when quantified using solvent standards showing significant matrix effect (ME) (≥ ±20%) even after 20× dilution. However, for the other pesticides ME was significantly eliminated on dilution. The recovery percentage improved for all pesticides on quantitation with matrix matched standards when compared with solvent standards. For pesticides with lower European Union (EU) maximum residue limits (MRLs), an experiment at lower spiking concentrations of 0.01 and 0.05 mg kg^-1 with lower dilutions (8×) reveals that almost all pesticides with lower EU MRLs (0.02 and 0.05 mg kg^-1 ) showed recoveries in the range 74-124% and relative standard deviation (RSD) less than 20%.

CONCLUSION

Theoretical limit of quantitation (LOQ) is proposed which ranged from 0.01 to 0.18 mg kg^-1 for matrix matched standards. An LOQ of 0.01 mg kg^-1 was easily achieved for the pesticides with lower EU MRLs with lower dilutions (8×) with exception of fipronil for which this can be achieved without dilution provided matrix matched standards are used. The method can be extended to other spices. © 2021 Society of Chemical Industry.

Multi-Residue Analysis of Chemical Additives in Edible Vegetable Oils Using QuEChERS Extraction Method Followed by Supercritical Fluid Chromatography

Since the quality and safety of food highly depend on its preservation and protection, the use of food packaging materials increases the risk of chemical contamination of the packaged food by migration. Herein, we focused on antioxidants, photoinitiators, UV absorbers and plasticizers which are extensive additives used in food packaging materials. In the present study, a rapid, simple, green and reliable method was developed and validated for the determination of twelve chemical additives in edible vegetable oils using SFC together with a modified QuEChERS procedure. Under the optimum conditions, twelve additives were separated within 10 min, and the consumption of the organic solvent was significantly reduced, which improved the environmentally friendliness. The performance of the developed method was evaluated. Good linearity (r > 0.999) was obtained in the range of 0.20−20.0 µg/mL and 0.50−20.0 µg/mL, respectively. The limits of detection and limits of quantification of the twelve additives in vegetable oils were 0.05−0.15 µg/mL and 0.15−0.50 µg/mL, respectively. Recoveries of all the chemical additives for the spiked samples were between 60.9% and 106.4%, with relative standard deviations (RSD) lower than 9.9%. The results demonstrated that the proposed method was efficient, reliable and robust for the routine analysis of additives in edible vegetable oils and can be an alternative to the multi-residue analysis of chemical additives for other packaged foods.

Critical Evaluation of Analytical Methods for the Determination of Anthropogenic Organic Contaminants in Edible Oils: An Overview of the Last Five Years

Anthropogenic contaminants, as pesticides, polycyclic aromatic hydrocarbons (PAHs) and monochloropropanediols (MCPDs), have become important to be controlled in edible oils, since their regular occurrence. In fact, alerts from the Rapid Alert System for Food and Feed (RASFF) in oils normally include these compounds. From a critical point of view, tools used to control these compounds in the last 5 years will be discussed, including sample preparation, analysis and current regulations. Extraction and analysis methods will be discussed next, being liquid-liquid extraction (LLE) and QuEChERS, with or without clean-up step, as well as chromatographic methods coupled to different analyzers (mainly mass spectrometry), the most commonly used for extraction and analysis respectively. Occurrence in samples will also be reviewed and compared with the legal maximum residue limits (MRLs), observing that 4%, 20% and 60% of the analyzed samples exceed the legal limits for pesticides, MCPDs and PAHs respectively.

Analytical methods for pesticide residues determination in propolis and propolis-based products

As a result of massive bee deaths in recent years, beekeeping is raising concerns about the presence of pesticides in propolis which is considered as a safe product. The paper is focused on the analysis of bee propolis and propolis-based products using various chromatographic techniques using mass spectrometry detection predominantly. An important part of the work is an overview concerning methods of sample preparation, extraction, and purification of extracts, followed by separation and detection techniques. Positive findings of contaminants and their concentrations in propolis samples and propolis products were evaluated. Sorption based techniques such as matrix solid phase dispersion and solvent-based extraction techniques are frequently applied for propolis analysis in connection with chromatographic techniques. Liquid-based extractions, such as the QuEChERS extraction technique (Quick, Easy, Cheap, Effective, Rugged, Safe), combine extraction by solvent with several ways of extract cleaning using combinations of salts and sorbents, primary secondary amine, MgSO4, NaCl, graphitized carbon, EMR-lipid, florisil, or octadecylsilane-modified silica gel. Other extraction techniques were reviewed. The most significant problem to be considered in pesticides detection is the topic of matrix effects, which have to be solved for each sample analysis with special care.

Easy and effective analytical method of carbendazim, dimethomorph, and fenoxanil from Protaetia brevitarsis seulensis using LC-MS/MS

Traditionally in Korea, Protaetia brevitarsis seulensis (white-spotted flower chafer) has been used as a medicine, and recently has attracted increased attention due to its antithrombotic efficacy. Some of spent mushroom compost or fermented oak sawdust, a feedstock for P. brevitarsis, were contaminated with three fungicides, carbendazim, dimethomorph, and fenoxanil, which could be transferred to the insect. This study was aimed to optimize a simple extraction method combined with liquid chromatography tandem mass spectrometry and apply it to the real samples. After the pulverized samples (5 g) were extracted with acetonitrile (10 mL) and formic acid (100 μL), fat and lipids in the samples were slowly precipitated at -20°C for 24 hours. After eight different clean-up methods were investigated, the mixture of 150 mg MgSO₄/25 mg PSA/25 mg C18 was selected due to optimal recovery of the target compounds. Recovery (77.9%‒80.8% for carbendazim, 111.2%‒116.7% for dimethomorph, and 111.9%‒112.5% for fenoxanil) was achieved with reasonable relative standard deviation (<5.5%) The analytical method developed in this study was used to analyze three compounds in the 24 insect samples donated by the insect farm owners but no target compounds were detected. These results can provide important data for establishing the pesticide safety standards for P. brevitarsis before the medical applications.

Simultaneous trace analysis of 10 benzophenone-type ultraviolet filters in fish through liquid chromatography-tandem mass spectrometry

We developed and validated a trace analytical method for the simultaneous determination of 10 benzophenone (BP)-type ultraviolet filters (BPs; BP, BP-1, BP-2, BP-3, BP-8, 2-hydroxybenzophenone [2-OHBP], 4-hydroxybenzophenone [4-OHBP], 4-methylbenzophenone [4-MBP], methyl-2-benzoylbenzoate [M2BB], and 4-benzoylbiphenyl [PBZ]) to analyze BPs in 110 commercial fish samples. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was employed. The developed method exhibited satisfactory linearity (R² > 0.993), favorable precision with intraday and interday relative standard deviation ranges of 1.0%-26.6% and 2.3%-29.3%, respectively, and a limit of detection ranging from 0.001 to 0.1 ng/g. BP and 2-OHBP were detected in 100% of the samples; BP-3, 4-OHBP, PBZ, and 4-MBP were detected in >70% of the samples; M2BB was detected in 33% of the samples, and BP-2 and BP-8 were not detected. Higher mean (minimum-maximum) levels of 2-OHBP and BP were found in fish samples with low lipid content, ranging from 18 (1.1-218.3) to 10 (0.5-45.4) ng/g, and those with high lipid content, ranging from 22 (1.5-76.4) to 9.6 (5.2-18.5) ng/g; low levels of the remaining six BPs were found, ranging from 0.01 to 0.9 ng/g. The mean 2-OHBP levels were 21.3, 14.4, and 30.2 ng/g for fish samples obtained from aquaculture in Taiwan, the wild in Taiwan, and different countries, respectively, with levels up to 218.3 ng/g (field eel) for a sample from Indonesia. BPs may not pose a health risk to Taiwanese adults through the consumption of fish; however, additional studies are needed to examine the risk that these contaminants may pose to ecosystems and human health.

Effective and rugged analysis of glyphosate, glufosinate, and metabolites in Tenebrio molitor larva (mealworms) using liquid chromatography tandem mass spectrometry

Tenebrio molitor larva (mealworms) has recently attracted attention as a protein source for food and feed. The larva is generally fed with wheat bran, which can be possibly contaminated with glyphosate. To establish food safe standards, a rugged and effective analytical method for glyphosate, aminomethylphosphonic acid, glufosinate, and their metabolites including 3-methylphosphinico-propionic acid, and N-acetyl glufosinate, in mealworms was optimized using liquid chromatography tandem mass spectrometry. An anionic polar pesticide column was used due to its high suitability for glyphosate. Acidified water and acetonitrile were used to extract the target compounds without contribution from various fatty and pigment interferences derived from brownish insects. Seven different clean-up procedures ((1) 50 mg C18 (2) 20 mg C18/Z-sep (3) PRiME hydrophilic-lipophilic balance (HLB) cartridge (4) 75 mg Z-sep, (5) 75 mg Z-sep+, (6) EMR-lipid cartridge, and (7) 50 mg ENVI-Carb) were compared. Due to its simplicity and cost-effectiveness, PRiME HLB was selected for clean-up. The recoveries of the target compounds were ranged from 86 to 96% with < 20% relative standard deviations. Therefore, this simple and effective method can be applied for the two pesticides and their metabolites in other edible insects or high-fat matrices.

Pesticide residues in fruits and vegetables from the southern part of Botswana

This study reports a surveillance of multi-pesticide residues of fruits and vegetables sold in the local markets carried out in 2018-2019 in Botswana to access consumer safety. A validated method for analysis of 232 pesticide residues in fruits and vegetables was applied, based on QuEChERS-GC-MS/MS methodology. A total of 83 fruit and vegetable sold in different markets were bought from three different areas of the southern region . Levels of pesticides ranged between 0.0032 ± 0.0009 mg/kg and 70.4 ± 19.4 mg/kg. A total of 78% of the samples contained pesticide residues, whereas only 13% of the samples violated the EU/Codex MRLs. In particular, rape vegetable samples exceeded legislative limits most, followed by cabbage, green pepper and tomato. The most frequently detected compounds were chlopyrifos, chlorfenapyr, tebuconazole, methamidophos and cypermethrin. These results will serve as a foundation for future studies, involving continuous monitoring programmes.

Development and validation of an analytical method for the multiresidue analysis of pesticides in sesame seeds using liquid- and gas chromatography with tandem mass spectrometry

For the first time, an analytical method for the multiresidue analysis of multiclass pesticides in sesame seeds using liquid- and gas chromatography with tandem mass spectrometry (LC-MS/MS and GC-MS/MS) was developed and validated. At first, the sample was comminuted after adding water (1:2 w/v). The sample preparation workflow included acetonitrile extraction, followed by freeze-out of the extract at -80°C with a subsequent cleanup by dispersive solid phase extraction (dSPE) (100 mg of C₁₈ + 150 mg of MgSO₄ for LC-MS/MS and 100 mg of C₁₈ + 25 mg florisil + 150 mg of MgSO₄ for GC-MS/MS). As noted, these cleanup steps were quite effective in removing the fatty co-extractives. The optimised sample preparation method effectively minimised the matrix effects and offered a limit of quantification (LOQ) of 0.01 mg/kg for most compounds. The LC-MS/MS and GC-MS/MS methods were validated at three levels (0.01, 0.02 and 0.05 mg/kg) for 222 and 220 compounds respectively. The method accuracy and precision complied with the performance criteria of the SANTE/12682/2019 analytical quality control procedure. The results of the intra-laboratory (involving six analysts) and inter-laboratory studies (involving eight accredited laboratories) were comparable for all pesticides. Considering its performance efficiency and alignment with the regulatory guidelines, this method can be implemented across the food testing laboratories for the monitoring of pesticide residues in sesame seeds.

Comparative evaluation of multi-residue methods for analysis of pesticide residues in black pepper by gas chromatography tandem mass spectrometry: critical evaluation of matrix co-extractives and method validation

A gas chromatography tandem mass spectrometry method was developed for simultaneous determination of 133 pesticides in Black pepper (Piper nigrum). QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) sample preparation method is preferred over multistep methods. Extraction was done by using acetonitrile followed by clean up using graphitized carbon, primary secondary amine and octadecyl silica (C₁₈). Even after the cleanup, non-volatile co-extractives stick to the liner and column which results in affecting the performance of the instrument and volatile co-extractives impact the analysis by enhancing the analyte concentration. So we evaluated a dilution procedure to overcome the drawbacks. The limit of quantification of 0.01 mg kg^-1 was achieved for fifty times diluted sample extract with S/N ≥ 10. The recovery was between 70 and 120% for 0.01, 0.025 and 0.05 mg kg^-1 for fortified samples and corresponding precision was between 3 and 16% RSD. The seven-level calibration curve shows a regression co-efficient of 0.99.

Optimization of a Simplified and Effective Analytical Method of Pesticide Residues in Mealworms (Tenebrio molitor Larvae) Combined with GC-MS/MS and LC-MS/MS

An effective analytical method was optimized for residues including chlorpyrifos-methyl, deltamethrin, fenoxanil, thiobencarb and fludioxonil in mealworms, the larval form of Tenebrio molitor. They are listed for pest control during wheat cultivation and can be found in wheat-bran feed for growing mealworms in South Korea. Analytes were extracted using acetonitrile and salt packet. Four clean-up methods ((1) MgSO₄ + 25 mg PSA + 25 mg C18; (2) MgSO₄ + 50 mg PSA + 50 mg C18; (3) EMR-lipid^TM tube; and (4) 10 mL n-hexane) were investigated and the method (1) was selected due to its robustness. Low-temperature precipitation of fat and proteins improved the recoveries. Recoveries from the Method (1) were satisfying with 70-120% with <20% relative SD at a spiking level of 0.01 mg/kg. With the simultaneous sample preparation, fenoxanil, thiobencarb and fludioxonil were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) and chlorpyrifos-methyl and deltamethrin by gas chromatography tandem mass spectrometry (GC-MS/MS). Quantification limits for LC-MS/MS and GC-MS/MS were 0.5 and 2.5 μg/L, respectively. No pesticides of interest were detected in 30 real samples collected across the nation. However, the data can be provided for establishing maximum residue limits for the pesticides in mealworms in response to the positive list system.

Response of soil bacterial and fungal community structure succession to earthworm addition for bioremediation of metolachlor

Synergistic biodegradation of earthworms and soil microorganisms plays a key role in the removal of organic pollutants in soil, yet microbially mediated processes remain unclear, especially regarding the succession of soil microbial interactions. Herein, soil biochemical evaluation, microbial community characterization, and interaction network construction were combined to understand the mechanisms dominating microbial community succession during synergistic bioremediation of metolachlor-polluted soils. The results of the network analysis indicated that metolachlor could render more complex relations but weaker connection strength among soil microorganisms. The addition of earthworms significantly alleviated the stress of metolachlor on soil microbial interactions and resulted in the restoration of interactions to a great extent. Additionally, the soil physicochemical properties, enzyme activities, and microbial community changed greatly with the addition of metolachlor and earthworms. Some soil microorganisms became significantly correlated with soil properties, metolachlor concentrations, and enzyme activities. These results, dominated by the succession of soil microbial communities, provide a new perspective for assessing the remediation effect of contaminated soil by organic pollutants.

Stimulation of earthworms (Eisenia fetida) on soil microbial communities to promote metolachlor degradation

Degradation of metolachlor in surface soil is extremely important to its potential mobility and overall persistence. In this study, the effects of earthworms (Eisenia fetida) on the degradation of metolachlor at two concentration levels (5 and 20 mg kg^-1) in soil were investigated via the column experiment. The degradation kinetics of metolachlor indicate that addition of earthworms enhances metolachlor degradation significantly (P < 0.05), with the enhanced degradation rate of 30% and 63% in the low and high concentration treatments at the 15th day, respectively. Fungi rather than bacteria are primarily responsible for metolachlor degradation in soil, and earthworms stimulate metolachlor degradation mainly by stimulating the metolachlor-degrading functional microorganisms and improving fungal community structure. Earthworms prefer to promote the possible fungal degraders like order Sordariales, Microascales, Hypocreales and Mortierellales and the possible bacteria genus Rubritalea and strengthen the relationships between these primary fungi. Two metabolites metolachlor oxanilic (MOXA) and moetolachlor ethanesulfonic acid (MESA) are detected in soil and earthworms in the high concentration treatments. Earthworms stimulate the formation of MOXA and yet inhibit the formation of MESA in soil. Another metabolite metolachlor-2-hydroxy (M2H) is also detected in earthworms, which is reported firstly. The study provides an important information for the remediation of metolachlor-polluted soil.

Dispersive Solid-Phase Extraction Using Microporous Sorbent UiO-66 Coupled to Gas Chromatography-Tandem Mass Spectrometry: A QuEChERS-Type Method for the Determination of Organophosphorus Pesticide Residues in Edible Vegetable Oils without Matrix Interference

A QuEChERS-type method without matrix interference was designed and developed to determine organophosphorus pesticide residues in edible vegetable oils, based on dispersive solid-phase extraction with cleanup using UiO-66 as sorbent. Microporous UiO-66 directly and selectively adsorbed organophosphorus pesticides and excluded interfering compounds. Clean analytes were obtained by elution and analyzed using gas chromatography-tandem mass spectrometry. The dispersive solid-phase extraction conditions (amount of adsorbent, extraction time, desorption solvent volume, and elution time) were optimized. The limits of detection of the pesticides in vegetable oils were 0.16-1.56 ng/g. Under optimized conditions, the average pesticide recoveries were 81.1-113.5%. The intraday and interday relative standard deviations for analyte recovery were <8.2 and <13.9%, respectively. Thus, the method is reliable and could detect organophosphorus pesticide residues in edible vegetable oils. Furthermore, UiO-66 can be easily recycled and reused at least 10 times, reducing the cost of analysis.

Novel sequential separation and determination of a quaternary mixture of fungicides by using an automatic fluorimetric optosensor

A versatile flow-through multi-optosensor is proposed for the separation and spectrofluorimetric determination of mixtures of four widely used pesticides: carbendazim, thiabendazole, carbaryl and o-phenylphenol at µg g^-1 levels in fruits. The flow system is based on the online pre-concentration and separation of the pesticides on a solid sensing microzone, followed by the sequential measurement of their native fluorescence. The separation of the pesticides takes place on a solid support located in the same flow cell, on which analytes are temporarily immobilized and separated from the matrix due to their different retention/desorption kinetics when they interact with the C₁₈ silica gel microbeads. Suitable analytical parameters were obtained for the selected analytes, with method detection and quantification limits ranging between 0.1-0.5 and 0.2-1.6 µg g^-1, respectively. These values comply with the maximum residue limits (MRLs) established by the Codex Alimentarius for these commodities; in addition, carbendazim, thiabendazole and ortho-phenylphenol comply with the MRLs of The European Union. The developed method was applied to the analysis of citrus fruits by performing recovery studies. Recoveries between 85% and 115% were obtained in all cases, and the results were confirmed by a liquid chromatography-mass spectrometry reference method.

Synthesis and application of molecularly imprinted silica for the selective extraction of some polar organophosphorus pesticides from almond oil

The aim of this work was to prepare and evaluate molecularly imprinted polymers obtained by a sol-gel approach for the selective solid-phase extraction (SPE) of organophosphorus pesticides (OPs) from almond oil. The performances of molecularly imprinted silicas (MISs), prepared using different conditions of synthesis, were studied by applying different extraction procedures in order to determine the ability of the MISs to selectively extract ten target OPs. For this, the retention of OPs on MISs in pure media was compared with the retention on a non-imprinted silicas (NISs), used as control sorbent, to prove the presence of specific cavities. The most promising MIS allowed the selective extraction of the 3 most polar OPs among the 10 studied. The capacity was studied and the repeatability of the extraction recovery yield was demonstrated both in pure and real media. This MIS was able to selectively extract fenthion sulfoxide and dimethoate contained in almond oil extract after applying the optimized extraction procedure with recovery yields between 100 and 114%. The estimated limit of quantification (LOQ, S/N = 10), thanks to LC/MS analysis in MRM mode, between 1.2 and 4.6 μg/kg for those OPs in the almond fruits, was more than 10 times lower than the Maximum Residue Levels (MRLs) established by the European Commission. This MIS therefore shows a high potential for the analysis of those two polar OPs at trace levels from almond oils.