Determination of Pesticide Residues in Vine Leaves Using the QuEChERS Method and Liquid Chromatography-Tandem Mass Spectrometry.

Commercial viticulture necessitates regular pesticide applications to manage diseases and pests, raising significant concerns regarding pesticide residues among stakeholders. Due to health risks associated with these residues in Turkish vine leaves, the European Commission has increased the frequency of official control from 20% to 50%. Thus, the aim of this study was to determine multi-class pesticide residues in brined vine leaves from Turkey. A total of 766 samples of vine leaves were collected between May 2022 and June 2023. More than 500 residues were analyzed using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, followed by liquid chromatography-tandem mass spectrometry. In-house validation data demonstrated that the analytical method exhibits fit-for-purpose performance in terms of linearity, accuracy, precision, and measurement uncertainty. Out of 766 samples analyzed, 180 samples (23.5%) contained one (131, 17.1%) or multiple (49, 6.4%) pesticides. Both the frequencies of occurrence and the rate of maximum residue level (MRL) exceedance increased in 2023 compared to 2022, with the MRL exceedance rate rising from 9.5% to 25.2%. Forty-three different residues were found in quantifiable concentrations and eight of them were non-approved. Among the residues, the non-systemic pyrethroid insecticides, lambda-cyhalothrin (8.0%) and cypermethrin (7.2%), were the two most frequently detected, with concentrations ranging from 0.010 to 0.248 mg kg-1 and from 0.011 to 0.533 mg kg-1, respectively. Turkey is a major exporter of vine leaves and these results provide crucial information regarding pesticide occurrence and quality assessment of vine leaves. The significant increase in both pesticide occurrence and MRL exceedance rates between 2022 and 2023 underscores the urgency for regulatory bodies to reassess current pesticide usage and monitoring practices. The findings emphasize the importance of implementing more stringent rules and improving enforcement methods in order to reduce the spread of unapproved pesticides and ensure adherence to global food safety standards.

Pesticides in soil, groundwater and food in Latin America as part of one health.

We here report of a conference about "Pesticides in Soil, Groundwater and Food in Latin America as part of One Health" that took place at the "IV Seminario Internacional de Sanidad Agropecuaria (SISA)" in Varadero, Cuba, 8-12 May 2023. Researchers of Latin America (Argentina, Brazil, Chile, Costa Rica, Colombia, Cuba, Mexico) and Switzerland (workshop initiator) held presentations about occurrence and effects of pesticides on the environment, human health, the replacement of highly hazardous pesticides (HHP) by agroecological alternatives and the agri-food value chain. In a subsequent round table discussion, the presenters identified deficits, needs, interests and opportunities. According to them, the lack of awareness of pesticide use affects the health and safety of workers applying the chemicals. Despite Latin America representing the main agricultural area in the world with a very intense pesticide use, monitoring data of pesticides in soil, surface and groundwaters, food, as well as in humans are missing. Risks of pesticides to humans should be assessed so that authorities can withdraw or limit within "short time" the access to corresponding formulations on the market. Also, communication is not state of the art and should be improved as, e.g. the teaching of workers and farmers, how to correctly use and apply pesticides or the briefing of decision makers. Pollinators suffer from multiple stressors not the least due to pesticides, and alternatives are badly needed. On the technical side, the different analytical methods to determine residues of active ingredients and transformation products in matrices of concern should be harmonized among laboratories.Seven future actions and goals were identified to overcome the above deficits. Next steps after the publishing of this conference report are to harmonize and complete the information status of the presenters by exchanging the results/data already present. Therefore, a platform of interaction to address issues described above and to enhance collaboration shall be created. Samples of different matrices shall be exchanged to harmonize the chemical analysis and establish interlaboratory comparisons. Such activities might be facilitated by joining international associations or organizations, where researchers can offer their expertise, or by forming a new pesticide network for Central and South America that could present tailored projects to national and international organizations and funding agencies.

Determination of 45 Pesticides in Avocado Varieties by the QuEChERS Method and Gas Chromatography-Tandem Mass Spectrometry.

Gas chromatography (GC) tandem mass spectrometry (MS/MS) stands as a preeminent analytical instrument extensively employed for the surveillance of pesticide residues in food. Nevertheless, these methods are vulnerable to matrix effects (MEs), which can potentially affect accurate quantification depending on the specific combination of analyte and matrix. Among the various strategies to mitigate MEs, matrix-matched calibration represents the prevailing approach in pesticide residue applications due to its cost-effectiveness and straightforward implementation. In this study, a total of 45 representative pesticides were analyzed in three different varieties of avocado (i.e., Criollo, Hass, and Lorena) using the Quick-Easy-Cheap-Effective-Rugged-Safe (QuEChERS) method with ammonium formate and GC-MS/MS. For this purpose, 5 g of the avocado sample was extracted with 10 mL of acetonitrile, and then 2.5 g of ammonium formate was added to induce phase separation. Subsequently, the supernatant underwent a cleanup process via dispersive solid-phase extraction employing 150 mg of anhydrous MgSO4, 50 mg of primary-secondary amine, 50 mg of octadecylsilane, 10 mg of graphitized carbon black, and 60 mg of a zirconium oxide-based sorbent (Z-Sep+). The GC-MS/MS analysis was successfully performed in less than 25 min. Rigorous validation experiments were carried out to assess the performance of the method. The examination of a matrix-matched calibration curve for each variety of avocado revealed that the ME remained relatively consistent and less than 20% (considered as a soft ME) for most pesticide/variety combinations. Furthermore, the method´s limits of quantification were lower than 5 µg/kg for all three varieties. Finally, the recovery values for most pesticides fell within the acceptable range of 70-120%, with relative standard deviation values below 20%.

Occurrence of Mycotoxins in Dried Fruits Worldwide, with a Focus on Aflatoxins and Ochratoxin A: A Review.

Dried fruits are popular and nutritious snacks consumed worldwide due to their long shelf life and concentrated nutrient content. However, fruits can be contaminated with various toxigenic fungal species during different stages, including cultivation, harvesting, processing, drying, and storage. Consequently, these products may contain high levels of mycotoxins. This risk is particularly pronounced in developed countries due to the impact of climate change. Several factors contribute to mycotoxin production, including the type of fruit, geographical location, climate conditions, harvest treatments, and storage management practices. The main mycotoxins in dried fruits are aflatoxins (AFs) and ochratoxin A (OTA), which can induce human health problems and economic losses. Mycotoxin contamination can vary significantly depending on the geographic origin of dried fruits (vine fruits, figs, dates, apricots, prunes, and mulberries). The aim of this review was to fill the knowledge gap by consolidating data from various regions to understand the global picture and identify regions with higher contamination risks. By consolidating research from various origins and stages of the supply chain, the review intends to shed light on potential contamination events during pre-harvest, drying, storage, and trading, while also highlighting the effects of storage conditions and climate change on mycotoxin contamination.

Pesticide Residues in Mandarins: Three-Year Monitoring Results.

The demand of plant production product use has increased because of the current system of citrus production, which prioritizes high agricultural yields. Therefore, the monitoring of pesticide residues in citrus fruits and other agricultural products and their impacts on human health and food security are of great concern. This study aims to determine multi-class pesticides including highly polar residues in satsuma mandarins. A total of 226 mandarin samples were collected over three consecutive harvesting years from 2019 to 2021 in the Izmir region of Turkey. Targeted compounds included pesticides and metabolites with European Union (EU) regulatory levels, plus other non-approved residues and highly polar compounds. The residues excluding highly polar substances were analyzed by applying the quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) determination for 434 analytes and gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) determination for 71 analytes. For six highly polar pesticides, sample preparation was based on Quick Polar Pesticides (QuPPe) extraction. The polar residues were determined by LC-MS/MS using internal standards. Forty different residues, including two highly polar substances, were recorded in mandarin samples through three harvesting years. In 8.4% of the samples, no quantifiable residues were detected, whereas 207 samples contained at least one residue. The maximum residue level (MRL) exceedances were recorded for 22.1% of the samples. The two most frequently found pesticides were phosphonic acid and spirotetramat, with an incidence rate of 48.7% and 46.5%, respectively. The concentration of phosphonic acid and spirotetramat in mandarin samples varied from 0.026 to 39.386 mg kg-1 and from 0.010 to 1.485 mg kg-1, respectively. The results will enable researchers and regulatory authorities to assess the extent of pesticide presence, identify potential risks, and take necessary measures to ensure the safety of satsuma mandarins for consumers.

Determination of 355 Pesticides in Lemon and Lemon Juice by LC-MS/MS and GC-MS/MS.

While pesticides have become a primary tool in modern agriculture, these compounds remain a high priority on the list of consumer concerns regarding food safety. The use of pesticides in the production and post-harvesting of lemon fruits is widely used to ensure agricultural yield and fruit quality. Therefore, monitoring studies on citrus fruits to enforce regulatory compliance and ensure food safety is in great demand. The aim of this study was to monitor multi-class pesticide residues in lemon fruits commercialized in Turkey. The transmission of residues that existed on the outer surface of the fruit into its juice was also studied. Whole fruits and lemon juice samples were prepared using the quick, easy, cheap, effective, rugged and safe (QuEChERS) methodology prior to analysis. For the screening and quantification of 355 pesticide residues, liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) were used. The analytical method has been shown to have a sufficiently low limit of quantification with respect to current maximum residue limits (MRLs) for all target analytes. The obtained recovery and precision parameters fulfilled the requirements in DG SANTE guidelines. The in-house validated analytical method was then applied for the determination of 355 pesticide substances in 100 whole fruit samples and their juices. Sixteen different residues were detected in 43% of lemon fruits, whereas 57 lemon samples were pesticide-free. The MRLs exceedances were recorded in 29 lemon samples. The most frequently detected (17%) pesticide in lemon fruits was chlorpyrifos-methyl, with a range of 0.013-0.098 mg kg-1. A lower frequency was detected for metamitron (10%, 0.027-0.118 mg kg-1), buprofezin (9%, 0.023-0.076 mg kg-1), pyriproxyfen (9%, 0.021-0.102 mg kg-1) and malathion (7%, 0.100-0.482 mg kg-1) in whole fruits. However, none of the pesticide residues were detected in lemon juice samples. These results showed that target analytes are unable to penetrate the lemon exocarp and/or endocarp.

Analysis of Organochlorine Pesticides in a Soil Sample by a Modified QuEChERS Approach Using Ammonium Formate.

Currently, the QuEChERS method represents the most widely used sample preparation protocol worldwide for analyzing pesticide residues in a broad variety of matrices both in official and non-official laboratories. The QuEChERS method using ammonium formate has previously proven to be advantageous compared to the original and the two official versions. On the one hand, the simple addition of 0.5 g of ammonium formate per gram of sample is sufficient to induce phase separation and achieve good analytical performance. On the other hand, ammonium formate reduces the need for maintenance in routine analyses. Here, a modified QuEChERS method using ammonium formate was applied for the simultaneous analysis of organochlorine pesticide (OCP) residues in agricultural soil. Specifically, 10 g of the sample was hydrated with 10 mL of water and then extracted with 10 mL of acetonitrile. Next, phase separation was carried out using 5 g of ammonium formate. After centrifugation, the supernatant was subjected to a dispersive solid-phase extraction clean-up step with anhydrous magnesium sulfate, primary-secondary amine, and octadecylsilane. Gas chromatography-mass spectrometry was used as the analytical technique. The QuEChERS method using ammonium formate is demonstrated as a successful alternative for extracting OCP residues from a soil sample.

Pesticide-Residue Analysis in Soils by the QuEChERS Method: A Review.

Pesticides are among the most important contaminants worldwide due to their wide use, persistence, and toxicity. Their presence in soils is not only important from an environmental point of view, but also for food safety issues, since such residues can migrate from soils to food. However, soils are extremely complex matrices, which present a challenge to any analytical chemist, since the extraction of a wide range of compounds with diverse physicochemical properties, such as pesticides, at trace levels is not an easy task. In this context, the QuEChERS method (standing for quick, easy, cheap, effective, rugged, and safe) has become one of the most green and sustainable alternatives in this field due to its inherent advantages, such as fast sample preparation, the minimal use of hazardous reagents and solvents, simplicity, and low cost. This review is aimed at providing a critical revision of the most relevant modifications of the QuEChERS method (including the extraction and clean-up steps of the method) for pesticide-residue analysis in soils.

Monitoring and Exposure Assessment of Fosetyl Aluminium and Other Highly Polar Pesticide Residues in Sweet Cherry.

Cherries are popular fruits due to their health benefits, organoleptic quality, and attractive appearance. Since highly polar pesticides are of low mass and amphoteric character, and are not amenable to traditional multi-residue extraction methods, they are more commonly not included in the pesticide monitoring program. This study aims to determine twelve highly polar pesticide residues in cherry samples intended for export from Turkey. A total of 16,022 cherry samples from 2018−2020 harvests in four production areas of Turkey were analyzed using a modification of the Quick Polar Pesticides method and liquid chromatography-tandem mass spectrometry. The method was validated at two fortification levels (0.01 and 0.05 mg kg−1), and good recoveries (87.4−111.4%) and relative standard deviations (<6%) were achieved for all analytes. The limits of quantification were in the range of 1.08−2.55 µg kg−1. Overall, 28.4% of the analyzed cherry samples were detected with phosphonic acid, calculated as fosetyl aluminium (fosetyl-Al) in amounts up to 77.7 mg kg−1. For 2304 samples (14.4%), the residues exceeded the European Union maximum residue level of 2 mg kg−1. There is no reason to be concerned about long-term exposure to phosphonic acid/fosetyl-Al, and the other highly polar pesticides through the consumption of sweet cherry.

The Role of Chromatographic and Electromigration Techniques in Foodomics.

Foodomics is the discipline aimed at studying the prevention of diseases by food, identifying chemical, biological and biochemical food contaminants, determining changes in genetically modified foods, identifying biomarkers able to confirm the authenticity and quality of foods or studying the safety, quality and traceability of foods, among other issues. It is mainly based on the use of genomic, transcriptomic, proteomic and metabolomic tools, among others, in order to understand the effect of food on animals and humans at the level of genes, messenger ribonucleic acid, proteins and metabolites. Since the first definition of Foodomics, a reasonable number of works have shown the extremely high possibilities of this discipline, which is highly based on the use of advanced analytical hyphenated techniques - especially for proteomics and metabolomics. This book chapter aims at providing a general description of the role of chromatographic and electromigration techniques that are currently being applied to achieve the main objectives of Foodomics, particularly in the proteomic and metabolomic fields, since most published works have been focused on these approaches, and to highlight relevant applications.

Covalent Organic Frameworks in Sample Preparation.

Covalent organic frameworks (COFs) can be classified as emerging porous crystalline polymers with extremely high porosity and surface area size, and good thermal stability. These properties have awakened the interests of many areas, opening new horizons of research and applications. In the Analytical Chemistry field, COFs have found an important application in sample preparation approaches since their inherent properties clearly match, in a good number of cases, with the ideal characteristics of any extraction or clean-up sorbent. The review article is meant to provide a detailed overview of the different COFs that have been used up to now for sample preparation (i.e., solid-phase extraction in its most relevant operational modes-conventional, dispersive, magnetic/solid-phase microextraction and stir-bar sorptive extraction); the extraction devices/formats in which they have been applied; and their performances and suitability for this task.

Determination of pesticides in dried minor tropical fruits from Colombia using the Quick, Easy, Cheap, Effective, Rugged, and Safe method-gas chromatography-tandem mass spectrometry.

The AOAC 2007.1 quick, easy, cheap, effective, rugged, and safe official method, together with gas chromatography coupled to a triple quadrupole mass spectrometer was applied for the analysis of 38 multiclass pesticides from dried fruits typically cultivated and exported from Colombia: uchuva (Physalis peruviana), lulo (Solanum quitoense), guanabana (Anona muricata), and pitahaya (Hylocereus undatus). The whole method was validated in terms of matrix-matched calibration, matrix effect, and recovery using atrazine-d5 as internal standard, triphenylphosphate for quality control of the injection, and a proper mixture of analytes protectants. Matrix-matched calibration data were found satisfactory for all pesticides and dried fruits, reporting R2 values above 0.99. Matrix effect values evidenced the existence of such effect in most cases. The applied procedure gave satisfactory recovery percentages (70-120%) and relative standard deviation values (< 20%) for 92% of the 456 combinations pesticide/fruit studied (spiked levels of 25, 200, and 400 µg/kg). Finally, 20 real dried fruit samples were analyzed and residues of tebuconazole were found in two samples of uchuva at a concentration below the lowest calibration level of the method for one of them and at 10.8 ± 1.6 µg/kg for the other, being below or similar to the general maximum residue level established for monitoring purposes in food applications.

Analysis of phthalic acid esters in sea water and sea sand using polymer-coated magnetic nanoparticles as extraction sorbent.

In this work, poly(dopamine)-coated magnetic nanoparticles (Fe3O4@pDA) have been used as sorbents for the magnetic dispersive solid-phase extraction (m-dSPE) of a group of 10 phthalic acid esters (dipropyl phthalate, DPP, dibutyl phthalate, DBP, dicyclohexyl phthalate, DCHP, bis(2-ethylhexyl)phthalate, DEHP, di-n-octyl phthalate, DNOP, diisodecyl phthalate, DIDP, butylbenzyl phthalate, BBP, diisononyl phthalate, DINP, diisopentyl phthalate, DIPP, di-n-pentyl phthalate, DNPP) and one adipate (di(2-ethylhexyl) adipate, DEHA) from sea water and sea sand extracts employing DBP-d4 and DHP-d4 as internal standards. After m-dSPE, analysis was carried out by gas chromatography mass spectrometry. Mean recovery values (which were determined at three concentration levels) ranged between 70 and 120%, with relative standard deviation values ≤ 20%, for nearly all analytes in both matrices. Matrix-matched calibration curves revealed the presence of matrix effects for certain PAEs, specially for sea sand, though linearity was assayed with determination coefficients (R2) above 0.991 for all target analytes. The limits of quantification of the method were in the range 1.8-319 ng/L for sea water and 0.020-4.0 ng/g for sea sand. Several samples of each type collected at different sites of the coast of Tenerife were also analysed. Only DEHA, DNOP and DIPP were detected in some of the sea sand samples at concentrations ≤ 44 ng/g.

Analysis of multiclass pesticides in dried fruits using QuEChERS-gas chromatography tandem mass spectrometry.

In this work, three versions of the QuEChERS method (original, AOAC 2007.01 and CEN 15662) were evaluated for the extraction of 38 multiclass pesticides from a mixture of five dried fruits: (strawberry, blackberry, passion fruit, pineapple and grapes) prior to their gas chromatography tandem mass spectrometry analysis. Among them, the AOAC 2007.01 method provided the best results in terms of lower amount of matrix co-extractives, matrix effect, extraction efficiency and precision. Its application to the analysis of the same pesticides in the individual dried fruits provided good recovery (between 70 and 120%) and relative standard deviation values (<20%) for most pesticides at three spiked levels. Matrix effect assessment revealed the necessity of taking into account such effect. Matrix-matched calibration data were also satisfactory for all analytes and matrices being the R2 ≥ 0.9900 and the lowest calibration level 5 µg/kg, which is lower than the agreed limit set at 10 µg/kg for monitoring purposes in food applications. Three samples of each type were also analysed, finding residues of metalaxyl, chlorpyrifos and iprodione in some of them.

High-throughput analysis of pesticides in minor tropical fruits from Colombia.

In this work, a method has been applied and validated for the determination of a group of 35 multiclass pesticides in the minor tropical fruits rose apple/pomarrosa (Syzygium malaccense), starfruit/carambola (Averrhoa carambola), yoyomo (Spondias purpurea) and papayuela (Vasconcellea pubescens) cultivated and exported in Colombia. The AOAC 2007.1 QuEChERS method, that uses an acetic acid/acetate buffer, was applied together with gas chromatography coupled to a triple quadrupole mass spectrometer. The method was validated in terms of calibration, recovery at three levels of concentration and matrix effects (MEs). A mixture of analyte protectants was also used. A good linearity was obtained in all cases, while the study of the ME revealed the need of developing matrix-matched calibration for many pesticides. Recovery values were in the range 70-120% with relative standard deviation values less than 20% for most of the pesticides studied. The lowest calibration level was 5 µg/kg. Several samples of each type were analysed.

Use of Basolite® F300 metal-organic framework for the dispersive solid-phase extraction of phthalic acid esters from water samples prior to LC-MS determination.

In the present work, a commercial metal-organic framework (Basolite® F300) has been applied for the first time as dispersive solid-phase extraction (dSPE) sorbent of eight phthalic acid esters (PAEs) (butyl benzyl phthalate, bis-2-n-butoxyethyl phthalate, bis-isopentyl phthalate, bis-n-pentyl phthalate, dicyclohexyl phthalate, di-(2-ethylhexyl) phthalate -DEHP-, di-n-octyl phthalate and diisononyl phthalate) and an adipate (bis (2-ethylhexyl) adipate), which is utilized as a PAE substitutive. Milli-Q, pond, tap and waste water were selected as samples. Dihexyl phthalate-3,4,5,6-d4 was used as procedural internal standard. High-performance liquid chromatography mass spectrometry was used for the determination of the target compounds. Optimum dSPE conditions were the following: 50 mL of the water sample (pH 6.0), 120 mg of sorbent and 15 mL of ACN as elution solvent. For the validation of the method, matrix-matched calibration and trueness of the method were addressed, obtaining determination coefficients (R2) higher than 0.9905 and relative recovery values between 70 and 118 % (RSDs < 20 %). The limits of quantification of the method were in the range 22-69 ng/L. Matrix effects were also studied. Different real samples were analysed, finding DEHP in all of them at the low µg/L level.

Study on the inhibitory effect of furafylline and troleandomycin in the 7-methoxyresorufin-O-demethylase and nifedipine oxidase activities in hepatic microsomes from four poultry species using high-performance liquid chromatography coupled with fluorescence and ultraviolet detection.

The present study reports the in vitro studies with furafylline and troleandomycin (TAO) as specific inhibitors of activities 7-methoxyresorufin-O-demethylase (MROD) and nifedipine oxidase, catalyzed by cytochrome P450 1 A2 (CYP1 A2) and 3A4 human enzymes, respectively, in hepatic microsomes of quail, duck, turkey and chicken. The results suggest that in chicken and quail the MROD activity is carried out by orthologs CYP1 A4 and 1 A5, meanwhile in duck and turkey by a CYP1 A5 ortholog. The nifedipine oxidase activity is carried out by orthologs of the CYP3A family in the four bird species. The use of furafylline and TAO significantly decreased these activities (P < 0.05) and suggested that the biotransformation of resorufin methyl ether (RME) may be related to more than one avian ortholog.

Determination of phthalic acid esters in water samples by hollow fiber liquid-phase microextraction prior to gas chromatography tandem mass spectrometry.

A new hollow fiber liquid-phase microextraction (HF-LPME) method has been developed for the extraction of a group of phthalic acid esters (PAEs) of interest from different water samples prior to gas chromatography tandem mass spectrometry analysis. HF-LPME was carried out using 1-octanol as extraction solvent followed by a back extraction step with cyclohexane. The different parameters that affect HF-LPME such as sample pH, ionic strength, extraction time, stirring rate, extraction temperature and back extraction conditions were investigated. The optimized conditions involved the extraction of 10 mL of sample without pH adjustment or addition of salt during 75 min under a stirring of 850 rpm at 60 °C and subsequent desorption with 200 µL of cyclohexane for 10 min in an ultrasonic bath. The method was validated in terms of calibration and recovery studies using dibutyl phthalate-d4 as internal standard. The developed procedure gave satisfactory recovery (74-120%) and relative standard deviation values (<20%) for the studied PAEs in mineral, tap, pond and waste water samples.

Recent applications of nanomaterials in capillary electrophoresis.

Nanomaterials have found an important place in Analytical Chemistry and, in particular, in Separation Science. Among them, metal-organic frameworks, magnetic and non-magnetic nanoparticles, carbon nanotubes and graphene, as well as their combinations, are the most important nanomaterials that have been used up to now. Concerning capillary electromigration techniques, these nanomaterials have also been used as both pseudostationary phases in electrokinetic chromatography (EKC) and as stationary phases in microchip capillary electrophoresis (CE) and capillary electrochromatography (CEC), as a result of their interesting and particular properties. This review article pretends to provide a general and critical revision of the most recent applications of nanomaterials in this field (period 2010-2017).

Dissipation kinetics of organophosphorus pesticides in milled toasted maize and wheat flour (gofio) during storage.

The dissipation/degradation of the pesticides dimethoate, terbufos, disulfoton, and pirimiphos-methyl were evaluated in milled toasted maize and wheat flour (gofio) during three months of storage. Their dissipation kinetics and residual levels were determined, as well as their possible decomposition into some of their main transformation products (disulfoton sulfoxide, terbufos sulfone and disulfoton sulfone). For this purpose, pesticide-free milled toasted maize and wheat samples were spiked with the pesticides, and they were then stored in the darkness at ambient temperature in a closed container to simulate current storage conditions of such packed food. A multiresidue analysis based on the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was performed for the simultaneous determination of these pesticides and their metabolites. After three months of storage, the dissipation of residues ranged between 34% (pirimiphos-methyl) and 86% (disulfoton) for maize gofio and between 69% (terbufos) and 92% (disulfoton and pirimiphos-methyl) for wheat gofio. The results demonstrated that the degradation was slower in gofio than in wheat gofio and that none of the selected metabolites were detected in any of the samples. Dissipation curves of all studied pesticides fitted to a first-order decay curve in both types of cereals.