Improvement and extension to new analytes of a multi-residue method for the determination of pesticides in cereals and dry animal feed using gas chromatography–tandem quadrupole mass spectrometry revisited

Multiresidue analysis of pesticides in three Indian soils: method development and validation using gas chromatography tandem mass spectrometry

The paper reports a multiresidue method that was validated on 220 multi-class pesticides in three major Indian soils, namely, (i) new alluvial soil (NAS); (ii) red lateritic soil (RS) and (iii) black soil (BS) from three different regions. An ethyl acetate-based extraction method with a freezing-out cleanup step was employed for sample preparation, followed by gas chromatography-tandem mass spectrometric analysis. The method that was initially optimized on BS worked satisfactorily for the other two soil matrices. At the spiking level of 10 µg/kg (LOQ), the recoveries were satisfactory (within 70-120%) with precision-RSDs, ≤20% (n = 6) for 85, 88.6, and 89% of compounds in BS, RS, and NAS respectively. At 20 µg/kg, the method performance was satisfactory in each soil for all pesticides. When this validated method was applied to analyse 25 field samples, 6 pesticides were detected in them. In each case, precision (RSD) was <20%. The method sensitivity, accuracy and precision complied with the SANTE/2020/12830 guidelines. The method can be applied for environmental monitoring and risk assessment purposes, thus aiding in regulating pesticide usage in agricultural fields. The limitations and future scope of the study are also discussed.HighlightsA multiresidue method is reported for simultaneous analysis of multi-class pesticides in diverse soilsThe method was validated on 220 pesticides in new alluvial, red lateritic and black soilsSample preparation involved extraction with ethyl acetate and cleanup by a freezing stepThe residues were estimated by gas chromatography tandem mass spectrometry (GC-MS/MS)The method accuracy and precision complied with the EU's SANTE guidelines.

Feed Safety and the Development of Poultry Intestinal Microbiota

Simple Summary

Intensive gut colonisation of animals starts immediately after birth or hatch. Oral route of colonisation, and consequently the first feed, plays a significant role in the continual defining of the intestinal microbial community. The feed can influence colonisation in two ways: providing the microbial inoculum and providing the nutritional requirements that suit a specific type of microbes. In combination with environmental factors, feed shapes animal’s future health and performance from the first day of life. The objective of this review was to investigate feed safety aspects of animal nutrition from the gut colonisation aspect.

Abstract

The first feed offered to young chicks is likely the most important meal in their life. The complex gut colonisation process is determined with early exposure and during the first days of life before the microbial community is formed. Therefore, providing access to high-quality feed and an environment enriched in the beneficial and deprived of pathogenic microorganisms during this period is critical. Feed often carries a complex microbial community that can contain major poultry pathogens and a range of chemical contaminants such as heavy metals, mycotoxins, pesticides and herbicides, which, although present in minute amounts, can have a profound effect on the development of the microbial community and have a permanent effect on bird’s overall health and performance. The magnitude of their interference with gut colonisation in livestock is yet to be determined. Here, we present the animal feed quality issues that can significantly influence the microbial community development, thus severely affecting the bird’s health and performance.

The application of rapid test paper technology for pesticide detection in horticulture crops: a comprehensive review

Background

The ever increasing pests and diseases occurring during vegetable crop production is a challenge for agronomists and farmers. One of the practices to avoid or control the attack of the causal agents is the use of pesticides, including herbicides, insecticides nematicides, and molluscicides. However, the use of these products can result in the presence of harmful residues in horticultural crops, which cause several human diseases such as weakened immunity, splenomegaly, renal failure, hepatitis, respiratory diseases, and cancer. Therefore, it was necessary to find safe and effective techniques to detect these residues in horticultural crops and to monitor food security.

Main body

The review discusses the use of conventional methods to detect pesticide residues on horticultural crops, explain the sensitivity of nanoparticle markers to detect a variety of pesticides, discuss the different methods of rapid test paper technology and highlight recent research on rapid test paper detection of pesticides.

Conclusions

The methodologies discussed in the current review can be used in a certain situation, and the variety of methods enable detection of different types of pesticides in the environment. Notably, the highly sensitive immunoassay, which offers the advantages of being low cost, highly specific and sensitive, allows it to be integrated into many detection fields to accurately detect pesticides.

QuEChERS Method Combined with Gas- and Liquid-Chromatography High Resolution Mass Spectrometry to Screen and Confirm 237 Pesticides and Metabolites in Cottonseed Hull

Cottonseed hull is a livestock feed with large daily consumption. If pesticide residues exceed the standard, it is easy for them to be introduced into the human body through the food chain, with potential harm to consumer health. A method for multi-residue analysis of 237 pesticides and their metabolites in cottonseed hull was developed by gas-chromatography and liquid-chromatography time-of-flight mass spectrometry (GC-QTOF/MS and LC-QTOF/MS). After being hydrated, a sample was extracted with 1% acetic acid in acetonitrile, then purified in a clean-up tube containing 400 mg MgSO4, 100 mg PSA, and 100 mg C18. The results showed that this method has a significant effect in removing co-extracts from the oily matrix. The screening detection limit (SDL) was in the range of 0.2–20 μg/kg, and the limit of quantification (LOQ) was in the range of 0.2–20 μg/kg. The recovery was verified at the spiked levels of 1-, 2-, and 10-times LOQ (n = 6), and the 237 pesticides were successfully verified. The percentages of pesticides with recovery in the range of 70–120% were 91.6%, 92.8%, and 94.5%, respectively, and the relative standard deviations (RSDs) of all pesticides were less than 20%. This method was successfully applied to the detection of real samples. Finally, this study effectively reduced the matrix effect of cottonseed hull, which provided necessary data support for the analysis of pesticide residues in oil crops.

Endocrine disruptors on and in fruits and vegetables: Estimation of the potential exposure of the French population

Fruits and vegetables are considered to be healthy compared to fats, carbohydrates, and meats. However, their production involves plant protection products (PPPs) or they can contain phytoestrogens which may exhibit endocrine effects. Thus, the exposure to the main PPPs and to phytoestrogens known as endocrine disruptors (EDs) is estimated. PPPs include fungicides, growth substances, herbicides, and insecticides authorised in France. ED-PPPs exposure is estimated from the maximum residue limits (MRLs) of 70 potential ED-PPPs used in France on 64 fruits and vegetables. The estimated exposure to potential ED-PPPs is 509 µg/d and involves agonist and antagonist substances in complex mixtures. Anti-androgens are preeminent, at 353 µg/d. Exposure to genistein and daidzein is calculated from 140 measurements in 9 categories of food-items containing soy. The global exposure to isoflavones in France is evaluated at 6700 µg/d. Phytoestrogen exposure is much higher than that of ED-PPPs. Their endocrine effects should be considered.

Development of a Modified QuEChERS Procedure for the Isolation of Pesticide Residues from Textile Samples, Followed by GC–MS Determination

Due to the use of pesticides during cotton production and/or textile storage, it is necessary to assure textile and clothing safety in order to improve the protection of human health. In this work, an efficient method was established for a multiresidue determination of 33 pesticides covering several pesticide classes such as organochlorine, organophosphate, pyrethroides, triazines, etc., in textiles by modified QuEChERS and followed by gas chromatography–mass spectrometry. Optimal conditions were selected, including the amount of the sample, type of the extraction solvent and cleaning up sorbents, until the method was finally validated. Sufficient accuracy and precision were presented by the method using spiked samples between 10 and 250 μg/kg, while recoveries from 70 to 120% and an RSD < 20% for all the pesticides were obtained; the limits of quantification were below 5 μg/kg for all studied pesticides. The presented method showed high separation efficiency with minimal sample and sorbent consumption. The validated method was successfully applied to the analysis of real samples and proved to be applicable to routine analyses.

Stable Indium Pyridylcarboxylate Framework with Highly Selective Adsorption of Cationic Dyes and Effective Nitenpyram Detection

On the basis of an undeveloped asymmetrical pyridylcarboxylate ligand, 2-(2-carboxypyridin-4-yl)terephthalic acid (H₃CPTA), an indium pyridylcarboxylate framework, [(Me)₂NH₂]_1.5[In_1.5(CPTA)₂]·5.5NMF·6H₂O (1), is synthesized under solvent thermal conditions. 1 displays a 3D anionic framework with a large void space, which contains open square channels with a cross section of 14.6 Å and a pore surface decorated with carboxylic oxygen atoms. Depending on the anionic skeleton and high water stability, 1 exhibits high adsorption selectivity and capacity for cationic dyes in aqueous solution. Furthermore, the luminescence performance illustrates that 1 has selectivity and sensitivity to nitenpyram with good recyclability.

Influence of different hydrophilic interaction liquid chromatography stationary phases on method performance for the determination of highly polar anionic pesticides in complex feed matrices

Hydrophilic interaction liquid chromatography is an alternative liquid chromatography mode for separation of polar compounds. In the recent years, this liquid chromatography mode has been recognized as an important solution for the analysis of compounds not amenable to reverse phase chromatography. In this work, we evaluated three different hydrophilic liquid chromatography stationary phases for the determination of 14 highly polar anionic molecules including pesticides such as glyphosate, glufosinate, ethephon and fosetyl, their main metabolites, and bromide, chlorate, and perchlorate. Several mobile phase compositions were evaluated combined with different gradients for the chromatographic run. The two columns that presented the best results were used to assess the performance for the determination of the 14 compounds in challenging highly complex feed materials. Very different matrix effects were observed for most of the compounds in each column, suggesting that different interactions can occur. Using isotopically labeled internal standards, acceptable quantitative performance and identification could be achieved down to 0.02 mg kg^-1 (the lowest level tested) for most compounds. While one column was found to be favorable in terms of scope (suited for all 14 compounds), the other one was more suited for quantification and identification at lower levels, however, not for all analytes tested.

Analysis of ethoxyquin residues in animal feed using QuEChERS and gas chromatography tandem mass spectrometry and its results from Catalonian production 2018-2019

Ethoxyquin (EQ) is a quinolone commonly used as an antioxidant additive and a fungicide. However, Regulation (EU) 2017/962 suspended its authorisation as a feed additive for all animal species and categories. The aim of this study is thus to ensure compliance with this regulation by developing a method of analysing EQ in animal feed. For analysis, EQ was extracted from animal feed by using a modified QuEChERS protocol that used an ascorbic acid buffer to minimise its degradation. The extracts were analysed by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QQQ), obtaining two chromatographic peaks corresponding to EQ and its transformation products. A study of these peaks was subsequently carried out using different standards, evincing that EQ had indeed been converted into several different transformation products. Quantification required the sum of the areas of the different peaks. The method was validated according to European Commission guidelines, namely SANTE/12682/2019. The obtainment of pesticide-free samples for carrying out the validation process was a critical achievement, as EQ residues were detected in 90% of the analysed samples. This was made possible by manufacturing 20 different feed samples from a mixture of several cereals used in animal feed in the laboratory. Method validation yielded excellent results in terms of accuracy (recoveries 70-120%), precision (RSD < 20%) and linearity (r²≥ 0.99) at the studied levels, as well as excellent sensitivity and selectivity (retention time ±0.1 min; ratio < 30%) to the LoQ. Over the course of 2018 and 2019, 70 samples of various feed matrices from agricultural production in Catalonia were analysed, garnering positive results 43% of the time.

Deposition amount and dissipation kinetics of difenoconazole and propiconazole applied on banana with two commercial spray adjuvants

A rapid and sensitive method for the simultaneous determination of difenoconazole and propiconazole residues in banana matrices was established using GC-MS/MS. The average recovery rates of difenoconazole and propiconazole from various matrices ranged from 76.7% to 94.9%. The relative standard deviation was between 0.9% and 7.4%. The effect of adding organosilicon and mineral oil adjuvants after being applied to the residues of difenoconazole and propiconazole in banana leaves was examined. The initial deposition amount 2 hours after the adjuvant treatment with organosilicon and mineral oil was 1.22–2.13 times higher than that after water treatment. After adding the two spray adjuvants, the residues of the two pesticides at 2 hours on three samples followed the order leaves > soil > fruit. The degradation half-lives of the two pesticides were in the range of 1.91–7.30 days for all the three treatments in two typical banana-growing areas in China. The degradation half-lives of the two pesticides in the water treatment group and the mineral oil treatment group were similar. However, organosilicon could apparently increase the half-life of difenoconazole on banana leaves. The final levels of difenoconazole and propiconazole residues on whole banana fruits were ≤0.1 mg kg⁻¹ (MRL) 14 days after application. The results of this work may aid the safe use of difenoconazole and propiconazole in banana production, especially when used with organosilicon and mineral oil adjuvants.

The effect of adding organosilicon and mineral oil adjuvants after being applied to the residues of difenoconazole and propiconazole in banana leaves was studied. The partition of the pesticides between soil, leaves and fruits was evaluated.

MS-Based Analytical Techniques: Advances in Spray-Based Methods and EI-LC-MS Applications

Mass spectrometry is the most powerful technique for the detection and identification of organic compounds. It can provide molecular weight information and a wealth of structural details that give a unique fingerprint for each analyte. Due to these characteristics, mass spectrometry-based analytical methods are showing an increasing interest in the scientific community, especially in food safety, environmental, and forensic investigation areas where the simultaneous detection of targeted and nontargeted compounds represents a key factor. In addition, safety risks can be identified at the early stage through online and real-time analytical methodologies. In this context, several efforts have been made to achieve analytical instrumentation able to perform real-time analysis in the native environment of samples and to generate highly informative spectra. This review article provides a survey of some instrumental innovations and their applications with particular attention to spray-based MS methods and food analysis issues. The survey will attempt to cover the state of the art from 2012 up to 2017.

Rapid and Simultaneous Analysis of 360 Pesticides in Brown Rice, Spinach, Orange, and Potato Using Microbore GC-MS/MS

A multiresidue method for the simultaneous and rapid analysis of 360 pesticides in representative agricultural produce (brown rice, orange, spinach, and potato) was developed using a modified QuEChERS procedure combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). Selected reaction monitoring transition parameters (e.g., collision energy, precursor and product ions) in MS/MS were optimized to achieve the best selectivity and sensitivity for a wide range of GC-amenable pesticides. A short (20 m) microbore (0.18 mm i.d.) column resulted in better signal-to-noise ratio with reduced analysis time than a conventional narrowbore column (30 m × 0.25 mm i.d.). The priming injection dramatically increased peak areas by masking effect on a new GC liner. The limit of quantitation was <0.01 mg/kg, and the correlation coefficients (r²) of matrix-matched standards were >0.99 within the range of 0.0025-0.1 mg/kg. Acetonitrile with 0.1% formic acid without additional buffer salts was used for pesticide extraction, whereas only primary-secondary amine (PSA) was used for dispersive solid phase extraction (dSPE) cleanup, to achieve good recoveries for most of the target analytes. The recoveries ranged from 70 to 120% with relative standard deviations of ≤20% at 0.01 and 0.05 mg/kg spiking levels (n = 6) in all samples, indicating acceptable accuracy and precision of the method. Seventeen real samples from local markets were analyzed by using the optimized method, and 14 pesticides in 11 incurred samples were found at below the maximum residue limits.

Multi-pesticides residue analysis of grains using modified magnetic nanoparticle adsorbent for facile and efficient cleanup

A facile, rapid sample pretreatment method was developed based on magnetic nanoparticles for multi-pesticides residue analysis of grains. Magnetite (Fe₃O₄) nanoparticles modified with 3-(N,N-diethylamino)propyltrimethoxysilane (Fe₃O₄-PSA) and commercial C18 were selected as the cleanup adsorbents to remove the target interferences of the matrix, such as fatty acids and non-polar compounds. Rice was used as the representative grain sample for method optimization. The amount of Fe₃O₄-PSA and C18 were systematically investigated for selecting the suitable purification conditions, and the simultaneous determination of 50 pesticides and 8 related metabolites in rice was established by liquid chromatography-tandem mass spectrometry. Under the optimal conditions, the method validation was performed including linearity, sensitivity, matrix effect, recovery and precision, which all satisfy the requirement for pesticides residue analysis. Compared to the conventional QuEChERS method with non-magnetic material as cleanup adsorbent, the present method can save 30% of the pretreatment time, giving the high throughput analysis possible.

Simultaneous Determination of Eight Pesticide Residues in Cowpeas by GC-ECD

A sensitive and effective method, using gas chromatography (GC) and an electron capture detector (ECD), for the simultaneous quantitative determination of bifenthrin, chlorothalonil, cyfluthrin, cypermethrin, difenoconazole, fenvalerate, procymidone and pyridaben residues in cowpea was developed and validated. The method involved extracting with acetonitrile, purification with a graphitized carbon black/amino solid phase extraction cartridge, and then determining by GC-ECD. Recovery studies were carried out at three spiked levels (0.01, 0.1 and 0.5 mg/kg). The average recoveries at the three spiked levels ranged from 76.6 to 107.0% with relative standard deviations in the range of 1.2-5.6% for all analytes. The quantification limit was 0.01 mg/kg for each pesticide and was less than or equal to the relevant MRLs set by China, the Codex Alimentarius or the European Union. The developed analyzing method was convenient, time and cost saving, environment-friendly and readily available than the traditional methods.

Ion-Mobility-Derived Collision Cross Section as an Additional Identification Point for Multiresidue Screening of Pesticides in Fish Feed

Ion mobility spectrometry allows for the measurement of the collision cross section (CCS), which provides information about the shape of an ionic molecule in the gas phase. Although the hyphenation of traveling-wave ion mobility spectrometry (TWIMS) with high-resolution quadrupole time-of-flight mass spectrometry (QTOFMS) has been mainly used for structural elucidation purposes, its potential for fast screening of small molecules in complex samples has not yet been thoroughly evaluated. The current work explores the capabilities of ultrahigh-performance liquid chromatography (UHPLC) coupled to a new design TWIMS-QTOFMS for the screening and identification of a large set of pesticides in complex salmon feed matrices. A database containing TWIMS-derived CCS values for more than 200 pesticides is hereby presented. CCS measurements showed high intra- and interday repeatability (RSD < 1%), and they were not affected by the complexity of the investigated matrices (ΔCCS ≤ 1.8%). The use of TWIMS in combination with QTOFMS was demonstrated to provide an extra-dimension, which resulted in increased peak capacity and selectivity in real samples. Thus, many false-positive detections could be straightforwardly discarded just by applying a maximum ΔCCS tolerance of ±2%. CCS was proposed as a valuable additional identification point in the pesticides screening workflow. Several commercial fish feed samples were finally analyzed to demonstrate the applicability of the proposed approach. Ethoxyquin and pirimiphos-methyl were identified in most of the analyzed samples, whereas tebuconazole and piperonil butoxide were identified for the first time in fish feed samples.

Fast gas chromatographic residue analysis in animal feed using split injection and atmospheric pressure chemical ionisation tandem mass spectrometry

Significant speed improvement for instrumental runtime would make GC–MS much more attractive for determination of pesticides and contaminants and as complementary technique to LC–MS. This was the trigger to develop a fast method (time between injections less than 10 min) for the determination of pesticides and PCBs that are not (or less) amenable to LC–MS. A key factor in achieving shorter analysis time was the use of split injection (1:10) which allowed the use of a much higher initial GC oven temperature. A shorter column (15 m), higher temperature ramp, and higher carrier gas flow rate (6 mL/min) further contributed to analysis-time reduction. Chromatographic resolution was slightly compromised but still well fit-for-purpose. Due to the high sensitivity of the technique used (GC–APCI-triple quadrupole MS/MS), quantification and identification were still possible down to the 10 μg/kg level, which was demonstrated by successful validation of the method for complex feed matrices according to EU guidelines. Other advantages of the method included a better compatibility of acetonitrile extracts (e.g. QuEChERS) with GC, and a reduced transfer of co-extractants into the GC column and mass spectrometer.

Evaluation of alternative sorbents for dispersive solid-phase extraction clean-up in the QuEChERS method for the determination of pesticide residues in rice by liquid chromatography with tandem mass spectrometry

Many compounds are used for pest control during the production and storage of rice, making it necessary to employ multiclass methods for pesticide residues determination. For this purpose, QuEChERS-based methods are very efficient, fast and accurate, and improvements in the clean-up step are important, especially for complex matrices, like cereals. In this work, different sorbents such as chitosan, florisil(®) , alumina, diatomaceous earth, graphitized carbon black, besides the commonly used primary secondary amine and octadecylsilane, were evaluated for dispersive solid-phase extraction clean-up in acetate-buffered QuEChERS method for the determination of residues of 20 representative pesticides and one metabolite in rice by liquid chromatography coupled to tandem mass spectrometry. The sorbent C18 presented the best results, however, chitosan showed similar results, and the best performance among the unconventional sorbents evaluated. The method limit of quantification, attending accuracy (70-120% recovery) and precision (RSD ≤20%) criteria, ranged from 5 to 20 μg/kg. Results showed that chitosan is an effective alternative to reduce analysis costs, maintaining the method reliability and accuracy.

Two-step dispersive-solid phase extraction strategy for pesticide multiresidue analysis in a chlorophyll-containing matrix by gas chromatography-tandem mass spectrometry

Two-step dispersive-solid phase extraction strategy for the cleanup of QuEChERS extracts in multiresidue analysis of current-use pesticides in a chlorophyll-containing matrix was evaluated and is reported for the first time. The proposed approach combines two sequential steps of dispersive-solid phase extraction (d-SPE) to reduce matrix co-extractives. In the first step, primary secondary amine (PSA) together with a new type of sorbent, known as ChloroFiltr, was employed. This was followed by a second step of d-SPE using octadecyl (C18) and graphitized carbon black (GCB). Also, new zirconium dioxide-based sorbents (Z-Sep+ and Z-Sep/C18) were evaluated but the use of GCB/C18 provided the highest pesticide coverage with recoveries in the range of 70-120% from spiked green soybean samples. The final extracts were analyzed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). The overall recoveries at three spiking levels of 0.01, 0.05 and 0.2 mg kg(-1) were 96±15%, 93±13% and 92±13% with relative standard deviations of 10±7%, 9±5%, and 11±5%, respectively. The proposed method provided matrix effect <20% for 77% of the target compounds, which may be considered as negligible because such variability is closed to the accepted repeatability. For the rest of 8 and 15% of the compounds, the matrix effect was 20-30% and >30%, respectively. The developed method was successfully applied to study dissipation patterns of pesticides applied to soybean in experimental plot trials, thus contributing to establish safe and proper use of pesticides by extension of authorization on minor crops in Poland.

A multiresidue screen for the analysis of toxicants in bovine rumen contents

Analysis of rumen contents is helpful in solving poisoning cases when ingestion of a toxic substance by cattle or other ruminant animals is suspected. The most common technique employs extraction of the sample with organic solvent followed by clean-up method(s) before analysis with gas chromatography–mass spectrometry equipped with a library of mass spectra to help identify unknowns. A rapid method using magnesium sulfate, primary secondary amine, and C18 sorbents following principles of QuEChERS to clean up rumen contents samples is reported herein. The method was validated to analyze fortified bovine rumen contents to detect commonly found organophosphorus pesticides, carbamates, and several other compounds such as atropine, 4-aminopyridine, caffeine, scopolamine, 3-chloro-4-methylaniline, strychnine, metaldehyde, and metronidazole. For each compound, the ratio of 2 ions from the mass spectrum was monitored in fortified rumen contents. The ion ratio of fortified sample was compared with the ion ratio of standard sample spectrum and was found to be within 20%, with the exception of aldicarb and 4-aminopyridine with ion ratio of 26% and 29%, respectively. Usefulness of the method was demonstrated by not only analyzing bovine rumen contents but also canine and avian gastrointestinal contents submitted for organic chemical screening.

Screening of pesticides and polycyclic aromatic hydrocarbons in feeds and fish tissues by gas chromatography coupled to high-resolution mass spectrometry using atmospheric pressure chemical ionization

This paper reports a wide-scope screening for detection and identification of pesticides and polycyclic aromatic hydrocarbons (PAHs) in feeds and fish tissues. QuEChERS sample treatment was applied, using freezing as an additional cleanup. Analysis was carried out by gas chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry with atmospheric pressure chemical ionization (GC-(APCI) QTOF MS). The qualitative validation was performed for over 133 representative pesticides and 24 PAHs at 0.01 and 0.05 mg/kg. Subsequent application of the screening method to aquaculture samples made it possible to detect several compounds from the target list, such as chlorpyrifos-methyl, pirimiphos-methyl, and ethoxyquin, among others. Light PAHs (≤4 rings) were found in both animal and vegetable samples. The reliable identification of the compounds was supported by accurate mass measurements and the presence of at least two representative m/z ions in the spectrum together with the retention time of the peak, in agreement with the reference standard. Additionally, the search was widened to include other pesticides for which standards were not available, thanks to the expected presence of the protonated molecule and/or molecular ion in the APCI spectra. This could allow the detection and tentative identification of other pesticides different from those included in the validated target list.

Polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PBDEs) and organochlorine pesticides in selected cereals available on the Polish retail market

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (DDT, HCH, HCB, chlordane, endrin, dieldrin, aldrin, nitrophene, metoxychlor) are man-made chemicals manufactured for numerous applications. The aim of this study was to assess levels of PCBs, PBDEs, and organochlorine pesticides in selected types of cereals available on the Polish retail market. 191 samples of various cereals have been analyzed in total. Average EC6 concentrations ranged from 56.4 (snacks) to 442.2 pg g(-1) (bran) while the concentration of 12 dioxin-like PCBs was in 15 (groats)-37.6 pg g(-1) (snacks) range. Mean dioxin equivalency concentration calculated as lower bound results in 2005 TEF values amounted to 0.120 ± 0.445 pg TEQ g(-1), while 0.091 ± 0.338 pg TEQ g(-1) if 1998 TEF values were used. Average concentration of all 14 studied BDEs (∑14 BDE) was 112 ± 80 pg g(-1), while average concentration of 13 BDEs excluding BDE #209 was only 15 ± 6 pg g(-1). Pesticide concentrations observed in the analyzed samples were generally low in comparison to maximum residue levels (MRLs) actually permitted by the European Union. However, MRLs were exceeded in 7 out of all 191 analyzed samples. Total concentration of DDT isomers in one of the tested bran samples was as high as 0.053 mg kg(-1). DMDT concentrations slightly above MRL = 0.01 mg kg(-1)were observed in 6 other samples (2 × bran, 1 × children porridge, 2 × snacks and 1 × bread). This study has shown that levels of PCBs, PBDEs and organochlorine pesticides in cereal products available on the Polish market are generally low. However, elevated levels of individual pollutants were observed in several instances.

Validation and use of a QuEChERS-based gas chromatographic-tandem mass spectrometric method for multiresidue pesticide analysis in blackcurrants including studies of matrix effects and estimation of measurement uncertainty

A triple quadrupole GC-QqQ-MS/MS method was optimized for multiresidue analysis of over 180 pesticides in blackcurrants. The samples were prepared by using a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) analytical protocol. To reduce matrix co-extractives in the final extract, the supernatant was cleaned up by dispersive-solid phase extraction (dispersive-SPE) with a mixture of sorbents: primary secondary amine (PSA), octadecyl (C18) and graphitized carbon black (GCB). The validation results demonstrated fitness for purpose of the streamlined method. The overall recoveries at the three spiking levels of 0.01, 0.05 and 0.2 mg kg(-1) spanned between 70% and 116% (102% on average) with relative standard deviation (RSD) values between 3% and 19% except for chlorothalonil (23%). Response linearity was studied in the range between 0.005 and 0.5 mg kg(-1). The matrix effect for each individual compound was evaluated through the study of ratios of the slopes obtained in solvent and blackcurrant matrix. The optimized method provided small matrix effect (<10%) for 77% of the compounds, whereas only for 14%, 5% and 4% compounds, the matrix effect was 10-20%, 20-30% and >30%, respectively. Following the application of "top-down" approach, the expanded measurement uncertainty was estimated as being 21% on average (coverage factor k=2, confidence level 95%). If compared with samples of other crops, the analyses of blackcurrants revealed a high percentage of exceedance of the legislative maximum residue levels (MRLs), as well as some instances of the detection of pesticides unapproved on this crop.

Direct liquid chromatography-tandem mass spectrometry determination of underivatized glyphosate in rice, maize and soybean

The residue determination of the widely used herbicide glyphosate (GLY) is highly problematic due to its amphoteric character, low mass and lack of chemical groups that might facilitate its detection. Most methods developed up to now have employed pre-column or post-column derivatization to form fluorescent derivatives and/or to reduce the polar character of the analyte facilitating its chromatographic retention. The aim of this work is to evaluate the feasibility of performing the direct LC-MS/MS determination of GLY residues in vegetables. After testing several Hydrophilic Interaction Liquid Chromatography (HILIC) columns, Obelisc N was selected due to its better chromatographic retention. LC-MS/MS determination has been performed in negative ionization mode, monitoring up to four transitions to give high reliability to the identification/confirmation process. This approach has been evaluated for the determination of GLY residues in rice, maize and soybean samples, and the method validated at different concentrations in compliance with the maximum residue limits established in the current legislation. After sample extraction with water, a combination of extract dilution, partition with dichloromethane, and solid phase extraction (SPE) using Oasis HLB cartridges (depending on the sample matrix under analysis) was applied. Quantification was made by using isotope-labeled GLY as internal standard and calibration in solvent. The methodology developed allows the rapid determination of GLY residues avoiding the derivatization step typically applied for this herbicide. The most critical issue is the robustness of the Obelisc N column, which was found to suffer rapid degradation with time. Extreme care and continuous testing of retention times and peak shapes is required for a reliable determination.