Matrix-Matching as an Improvement Strategy for the Detection of Pesticide Residues

Multiresidue analysis of pesticides in four different pomegranate cultivars: Investigating matrix effect variability by GC-MS/MS and LC-MS/MS

Matrix effect (ME) is unavoidable in multiresidue pesticide analysis, even when using highly advanced instruments, and differences in MEs can affect residue analytical accuracy due to pomegranate cultivar composition variations. However, literature to support this claim is limited.The study used GC-MS/MS and LC-MS/MS to investigate four different Indian pomegranate cultivar extracts and their MEs on multi-class pesticides.The whole fruit and arils of all cultivarswere tested for 22 GC-amenable and 21 LC-amenable pesticides. Principal component analysis of the data confirmed that each cultivar had unique MEs for each pesticide.The majority of pesticides showed acute variations in recovery rates with 95% confidence, while GC-MS/MS-amenablepesticides showed more variation. Although extrapolative dilution reduced the influence of MEs on analytical accuracy, a generalized matrix-matching for all cultivars was not possible to achieve.To reduce the variability in MEs, it is recommended that a cultivar-specific matrix-matched standard should be used.

Interaction between Six Waxy Components in Summer Black Grapes (Vitis vinifera) and Mancozeb and Its Effect on the Residue of Mancozeb

Mancozeb, an antifungal typically used for the growth of fruits, has the characteristic of non-internal absorption, and has a risk of binding to the waxy components of fruits. This work investigated the interaction of pesticide molecules with the waxy layer on the grape surface and their effects on pesticide residues in grapes. The study observed significant changes in the compositions of the waxy layer on the grape surface after soaking in a mancozeb standard solution. The six substances-oleanolic acid, ursolic acid, lupeol, octacosanol, hexacosanal, and γ-sitosterol-with discernible content differences were chosen for molecular docking. Docking results were further visualized by an independent gradient model based on Hirshfeld partition (IGMH). Hydrogen bonds and van der Waals forces were found between mancozeb and the six waxy components. Moreover, the negative matrix effects caused by the presence or absence of wax for the determination of mancozeb were different through the QuEChERS-HPLC-MS method. Compared with the residue of mancozeb in grapes (5.97 mg/kg), the deposition of mancozeb in grapes after dewaxing was significantly lower (1.12 mg/kg), which further supports that mancozeb may interact with the wax layer compositions. This work not only provides insights into the study of the interaction between pesticides and small molecules but also provides theoretical guidelines for the investigation of the removal of pesticide residues on the surface of fruits.

Comparison of pesticide residue and specific nutrient levels in peeled and unpeeled apples

BACKGROUND

Studies have shown that the consumption of apples has a beneficial effect on cardiovascular diseases and some cancers, largely as a result of their micronutrient and phytoconstituent contents. Apple peel not only contains more polyphenols than the flesh, but also is likely to contain pesticide residues. The present study aimed to compare the contents of certain micronutrients and residual pesticide levels in peeled and unpeeled apples.

RESULTS

Peeled apples contained fewer pesticide residues at lower concentrations than unpeeled apples. However, whether samples were peeled or not, the exposure values for pesticide residues in apples never exceeded the acceptable daily intake (ADI), but ranged between 0.04% and 2.10% of the ADI in adults for food intake estimated at the 95th percentile (277 g per person per day). Determination of polyphenol, fibre, magnesium and vitamin C levels showed that the nutritional differences observed between peeled and unpeeled apples were marginal.

CONCLUSION

The consumption of apples, such as the apples tested in the present study, results in an exposure to pesticides that is low for unpeeled apples, and lower for peeled apples. Moreover, there was no significant loss of nutritional value from eating peeled apples based on the nutrients investigated. © 2022 Society of Chemical Industry.

Pesticide Residues in Commonly Consumed Vegetables in Henan Province of China in 2020

Background

Pesticides are widely used in agricultural production to control insect pests and regulate plant growth in China, which may result in the presence of some pesticide residues in the vegetables. However, few studies of monitoring pesticides have been conducted in Henan Province. The aim of this study was to evaluate the level of pesticide residues in commonly consumed vegetables in the regions of Henan Province.

Methods

In this study, we collected 5,576 samples of 15 different vegetables in 17 areas from Henan Province during 2020. Eight kinds of pesticides were analyzed by gas chromatography-mass spectrometry (GC-MS), including procymidone, lambda-cyhalothrin, cypermethrin, pendimethalin, isocarbophos, isazophos, fenthion and deltamethrin. The chi-square test was used to compare the detection rates of pesticide residues in different regions.

Results

Of all the pesticides above, procymidone, lambda-cyhalothrin, cypermethrin, pendimethalin and isocarbophos were detected in vegetables, the detection rates were 27.0%, 16.2%, 11.4%, 3.5%, and 1.9%, respectively. However, isazophos, fenthion, and deltamethrin were not detected. In addition, procymidone, lambda-cyhalothrin, and cypermethrin were detected in urban areas, while pendimethalin was detected in rural areas. The detection rates of cypermethrin and pendimethalin in rural were 19.8% and 5.4%, respectively, which in urban were at relatively lower levels (13.7% and 1.9%, respectively) (P < 0.05). Compared the differences of pesticide detection rates among five areas of Henan province, we found that there were statistical differences in the detection rates of procymidone, cypermethrin and lambda-cyhalothrin in different regions (all P < 0.05).

Conclusion

The results have revealed that the pesticide residues are present. Higher detection rates and more types of pesticides were found in rural areas than urban areas. In addition, there were higher detection rates in Eastern Henan. The findings provided valuable information on the current pesticide residues status, which can be a reference of pesticide supervision and management.

Current Role of Mass Spectrometry in the Determination of Pesticide Residues in Food

The extensive use of pesticides represents a risk to human health. Consequently, legal frameworks have been established to ensure food safety, including control programs for pesticide residues. In this context, the performance of analytical methods acquires special relevance. Such methods are expected to be able to determine the largest number of compounds at trace concentration levels in complex food matrices, which represents a great analytical challenge. Technical advances in mass spectrometry (MS) have led to the development of more efficient analytical methods for the determination of pesticides. This review provides an overview of current analytical strategies applied in pesticide analysis, with a special focus on MS methods. Current targeted MS methods allow the simultaneous determination of hundreds of pesticides, whereas non-targeted MS methods are now applicable to the identification of pesticide metabolites and transformation products. New trends in pesticide analysis are also presented, including approaches for the simultaneous determination of pesticide residues and other food contaminants (i.e., mega-methods), or the recent application of techniques such as ion mobility–mass spectrometry (IM–MS) for this purpose.

Application of a Validated Method for the Identification and Quantification of Mycotoxins in Wines Using UPLC-MS/MS

The aim of the present study was to develop a rapid, simple and reliable method for the identification and quantification of six mycotoxins in wine using liquid chromatography with electrospray ionization tandem mass spectrometry. The analytical method was fully validated, and calibration curves were made with correlation coefficients >0.9970. A short analysis time and acceptable extraction efficiency were achieved by a direct extraction method of analytes (ochratoxin A, aflatoxin B1, B2, G1, G2 and Zearalenone) with acetonitrile. LOD values were from 0.03 to 0.27 μg kg−1, and LOQ values were from 0.08 to 0.81 μg kg−1, with recoveries at various values from 77 to 108%. The expanded uncertainty was 5–21% expressed at a coverage level of k = 2, at a confidence level of approximately 95%. The performance criteria of the method were fully met according to European legislation (EC) 401/2006. The method was successfully applied to wine samples from Cyprus. The method was simple, low cost, quick, accurate, and sensitive.

Overview, consequences, and strategies for overcoming matrix effects in LC-MS analysis: a critical review

The high-performance liquid chromatography-mass spectrometry (LC-MS) technique is widely applied to routine analysis in many matrices. Despite the enormous application of LC/MS, this technique is subjected to drawbacks called matrix effects (MEs) that could lead to ion suppression or ion enhancement. This phenomenon can exert a deleterious impact on the ionization efficacy of an analyte and subsequently on the important method performance parameters. LC-MS susceptibility to MEs is the main challenge of this technique in the analysis of complex matrices such as biological and food samples. Nowadays, the assessment, estimation, and overcoming of the MEs before developing a method is mandatory in any analysis. Two main approaches including the post-column infusion and post-extraction spike are proposed to determine the degree of MEs. Different strategies can be adopted to reduce or eliminate MEs depending on the complexity of the matrix. This could be done by improving extraction and clean-up methods, changing the type of ionization employed, optimization of liquid chromatography conditions, and using corrective calibration methods. This review article will provide an overview of the MEs as the Achilles heel of the LC-MS technique, the causes of ME occurrence, their consequences, and systemic approaches towards overcoming MEs during LC-MS-based multi-analyte procedures.

[Comparison of Validation Results Obtained by GC-MS/MS and LC-MS/MS for the Analysis of Residual Pesticides in Agricultural Products]

In the field of food analysis and regulation, different instruments are used to determine the accuracy of quantification values. This is essential, as inconsistencies in values are commonly encountered. To visualize the degree of these discrepancies in each food matrix, we compiled a validation study based on a routine method developed in our laboratory, for 121 pesticides in six agricultural products, namely the grapefruit, potato, paprika, cabbage, spinach, and brown rice. These were analyzed by GC-MS/MS and LC-MS/MS, and the results were compared mainly on the basis of trueness. According to the results of the validation study when using GC-MS/MS, of the 121 pesticides tested in each product class, the number of analytes that satisfied the criteria of the Japanese validation guidelines was 97 in grapefruit, 111 in potato, 110 in paprika, 118 in cabbage, 111 in spinach, and 63 in brown rice. In contrast, in the analysis of the same samples by using LC-MS/MS, the number of analytes that satisfied the criteria of the validation guidelines was 50 in grapefruit, 114 in potato, 103 in paprika, 112 in cabbage, 100 in spinach, and 103 in brown rice. Inconsistences in the differences of trueness were mainly attributed to matrix effects of each instrument, as well as to food matrices, of which the most diverged matrix was that of brown rice (over 20%).

Analytical Method for Pesticides in Avocado and Papaya by Means of Ultra-High Performance Liquid Chromatography Coupled to a Triple Quadrupole Mass Detector: Validation and Uncertainty Assessment

In this work, the uncertainty estimation for the determination of ametryn, carbofuran, atrazine, carbaryl, and methyl parathion in papaya and avocado is presented, along with other validation parameters. The analytical method was developed using Quick, Easy, Cheap, Effective, Rugged, and Safe extraction and ultrahigh performance liquid chromatography coupled to a triple quadrupole mass detector. The method validation showed that the linear correlation coefficients were higher than 0.99 for both fruits. The limits of detection for avocado and papaya were in the range of 0.022 to 0.46 and 0.003 to 0.109 μg/g, respectively. Intermediate precision varied from 5.3% to 13.0% in papaya, and from 4.8% to 20.2% in avocado. Recoveries obtained for each pesticide in both matrices ranged between 61.3% and 119.0%. Matrix effect was calculated for all compounds in both fruits. Finally, the overall uncertainty was lower than 36% for both fruits.

PRACTICAL APPLICATION

The present analytical method could be used for pesticides determination in different kind of fruits as papaya and avocado and as a practical guide for uncertainty and matrix effect determination.

Validation of a QuEChERS-Based Gas Chromatography-Mass Spectrometry (GC-MS) Method for Analysis of Phthalate Esters in Grain Sorghum

A modified QuEChERS method coupled with gas chromatography-mass spectrometry (GC-MS) was developed for analysis of 14 phthalate esters (PAEs) in grain sorghum (GS). Chemical extraction was done with acetonitrile followed by dispersive-solid phase extraction technique with a mixture of sorbents including primary secondary amine and octadecyl silica. Under the optimized condition, the matrix-matched calibration curves for all PAEs showed good linear relationship in the concentration range between 5 and 500 μg/L with correlation coefficients (R² ) better than 0.99. Mean recoveries were between 82.0% and 120.2% at spiking levels of 0.06, 0.6, and 2.0 mg/kg with RSD of 0.3% to 7.8% (n = 5) for intra-day precision and 1.2% to 7.6% (n = 5) for inter-day precision. The LOD_GS and LOQ_GS for 14 PAEs were between 0.4 and 10.0 μg/kg and 0.5 and 20.0 μg/kg, respectively. Analysis of 32 commercial GS samples revealed that dimethyl-, diethyl-, diisobutyl-, dibutyl-, and di- (2-ethylhexyl) phthalate esters were detected in all of the analytes. In addition, content-color scale model was applied to visualize the concentration differences of PAEs in real GS samples. Principal component analysis of PAEs revealed that the GS samples did not have a distinctive cluster based on their geographic origins. The established method was proven to be simple, accurate, and effective for analysis of PAEs in GS, which might also be applied for analysis of PAEs in other matrices.

PRACTICAL APPLICATION

A modified QuEChERS-based GC-MS method was developed for the determination of phthalate esters (PAEs) in grain sorghum (GS). The ubiquitous presence of PAEs can migrate into GS. Therefore, evaluation of the total content of PAEs in GS is helpful to understand its impact of overall pollution level on other foods. This study has provided some basic information in terms of the content and contamination of PAEs in GS, which is helpful to establish relevant standards and risk assessment of GS for the government.

Direct quantification of gamma H2AX by cell-based high throughput screening for evaluation of genotoxicity of pesticides in a human thyroid cell lines

Genotoxicity is thought to be the cause of many cancers. Genotoxicity due to environmental toxins may be partly responsible for the dramatic increase in the incidence of papillary thyroid cancer over the past two decades. Here, we present a fully automatable assay platform that directly quantifies the phosphorylation of nuclear histone gamma H2AX (γH2AX), a specific cellular marker for DNA double strand breaks (DSBs) via immunohistochemistry and laser scanning cytometry. It multiplexes γH2AX with total cell number measured as propidium iodide and calculates the percentage of cells with DSBs. Validation of this assay using NTHY-ori-3-1 human thyroid cells and etoposide showed that it was an excellent choice for high throughput applications. We used the assay to test the genotoxic effects of the EPA Toxcast Phase 1 pesticide library of 309 compounds. Compounds were evaluated in dose response and the DSB was quantified. We found that 19 pesticides induce DSB in vitro, highlighting a need to further assess these pesticides for their long-term oncogenic effects on the thyroid gland. Environ. Mol. Mutagen. 58:522-528, 2017. © 2017 Wiley Periodicals, Inc.