Multi-residue analysis of 203 pesticides in strawberries by liquid chromatography tandem mass spectrometry in combination with the QuEChERS method

Terminal Residues and Risk Assessment of Spiromesifen and Spirodiclofen in Tomato Fruits

Insecticides are important to increase crop yields, but their overuse has damaged the environment and endangered human health. In this study, residues of spiromesifen and spirodiclofen were determined in tomato fruit using a simple and efficient analytical procedure based on acetonitrile extraction, extract dilution, and UPLC-MS/MS. The linearity range was 1-100 µg/kg and 0.5-100 µg/kg, and the correlation coefficient (R²) and residuals were ≥0.9991 and ≤16.4%, respectively. The limit of determination (LOD) was 0.26 and 0.08 µg/kg, while the limit of quantification (LOQ) was verified at 5 µg/kg. The relative standard deviation of spiked replicates at 5 µg/kg analyzed in one day (RSDr, n = 6) was ≤8.35%, and within three different days (RSDR, n = 18) it was ≤15.85%, with recoveries exceeding 91.34%. The method recovery test showed a satisfactory value of 89.23-97.22% with an RSD of less than 12.88%. The matrix effect was determined after a 4-fold dilution of the raw extract and was -9.8% and -7.2%, respectively. The validated method was used to study the dissipation behavior of the tested analytes in tomato fruit under field conditions. First-order kinetics best described the dissipation rates. The calculated half-lives were 1.49-1.83 and 1.91-2.38 days for spiromesifen and spirodiclofen, respectively, after application of the authorized and doubled authorized doses, indicating that spiromesifen dissipated more rapidly than spirodiclofen. The final residue concentrations of spiromesifen and spirodiclofen were 0.307-0.751 mg/kg and 0.101-0.398 mg/kg, respectively, after two or three applications, and were below the European Union (EU) maximum residue limits. The chronic risk assessment indicates that both insecticides are safe for adult consumers.

Multi-Pesticide Residue Analysis Method Designed for the Robot Experimenters

Robots replacing humans as the executioners is crucial work for intelligent multi-pesticide residue analysis to maximize reproducibility and throughput while minimizing the expertise required to perform the entire process. Traditional analysis methods are predicated on manual execution, so we configured our robot experimenter, automated the analytical workflow, and achieved the goal of robotics execution. Our robot experimenter with an X-Y-Z axis robotic arm was interfaced with seven modules and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for automated standard solution preparation, sample pre-treatment, and UPLC-MS/MS detection. An algorithm was established to make the prepared matrix-matched standard solutions meet the monitoring requirements. The strategy was demonstrated and validated for the detection of 325 pesticides in 4 typical food matrices, suggesting that the developed method is applicable for the analysis of pesticide residues in vegetables and tea as part of regulatory monitoring programs and other purposes.

Single-atom Ce-N-C nanozyme bioactive paper with a 3D-printed platform for rapid detection of organophosphorus and carbamate pesticide residues

Rapid detection of pesticide residues based on enzyme mimics has recently attracted much interest. However, most nanozymes have low activity. Herein, a "single-atom Ce-N-C nanozyme" (SACe-N-C nanozyme) was rationally devised and verified to mimic peroxidase (POD-like) with superior activity. Based on its high POD-like activities and cascaded catalytic reactions with acetylcholinesterase (AChE), we constructed a bioactive paper for the detection of pesticide residues, which offered a portable approach to monitor fruits and vegetables within 30 min. More importantly, a 3D printed platform was integrated on the basis of SACe-N-C bioactive paper to achieve on-site portable testing of omethoate, methamidophos, carbofuran, and carbosulfan, showing limits of detection (LODs) of 55.83, 71.51, 81.81, and 74.98 ng/mL, respectively. The recovery rates were 84.09-104.68%. This study provided new insight into the design of novel single-atom nanozymes for cascaded catalytic detection and other rapid detection applications with high efficiency and low cost.

[Determination of plant growth regulators in animal-derived foods using QuEChERS-isotope-labeled internal standards with high performance liquid chromatography-tandem mass spectrometry]

As among the most widely used pesticides in agriculture, plant growth regulators (PGRs) have a positive influence on plants. However, the overuse of PGRs may induce toxicity in food and even be hazardous to human health. Numerous studies have investigated the presence and residues of PGRs on vegetables and fruits. Animal-derived foods are one of the most dominant food sources providing nutrients to fulfil the daily dietary intake, and could also be potentially contaminated by PGRs. However, there is little information on PGR residues in animal-derived foods. Standardization also lacks among the techniques for PGR determination in animal-derived foods, thereby restricting the further establishment of pesticide usage and food safety regulations. Therefore, in this study, a rapid and effective method for analyzing chlormequat chloride, thidiazuron, and paclobutrazol in animal-derived food samples was established. The method primarily involves high performance liquid chromatography-tandem mass spectrometry combined with the use of isotope-labeled internal standards. The extraction and clean-up procedures were based on the QuEChERS method. The analytes were extracted from pork, beef, chicken, pork liver, egg, and milk samples using acetonitrile, followed by 4 g anhydrous magnesium sulfate (MgSO₄), and 1 g sodium chloride (NaCl). The supernatant was removed using a mixture of 50 mg N-propyl ethylenediamine (PSA), 50 mg octadecyl silane (C18), and 150 mg MgSO₄, and then passed through a 0.22 μm membrane filter before determination. The Agilent ZORBAX Eclipse Plus C18 column (150 mm×3.0 mm, 1.8 μm) was used to separate the analytes under a gradient elution program, with acetonitrile and 5 mmol/L ammonium acetate solution as mobile phases. The analytes were detected by mass spectrometry using the positive and negative electrospray ionization modes under the multiple reaction monitoring mode. Matrix-matched calibration combined with internal standards was used to quantify the PGRs. The linear regression correlation coefficients (r²) for the PGRs were all greater than 0.990 in the corresponding linear concentration ranges. Chlormequat chloride, thidiazuron, and paclobutrazol showed good linearities in the range of 0.1-100 μg/L for the egg and pork liver samples and 0.1-50 μg/L for the pork, beef, and chicken samples. For the milk samples, thidiazuron and paclobutrazol showed good linearities in the range of 0.05-10 μg/L, while chlormequat chloride showed linearity in the range of 0.05-5 μg/L. The limit of detection (LOD) and limit of quantification (LOQ) for each PGR were based on the signal-to-noise (S/N) ratios. Under optimal conditions, the LODs ranged from 0.01 μg/kg to 0.1 μg/kg, where the LOD was defined as the amount of the tested compound that generated an S/N ratio higher than 3. In addition, the LOQs were in the range of 0.5-5 μg/kg, with an S/N ratio higher than 10. The precision and accuracy were evaluated by recovery experiments. At the LOQ, twice the LOQ, and 10 times the LOQ, the mean recoveries were in the range of 70.0%-117.4%, and the relative standard deviations (RSDs) ranged from 0.8% to 16.1%. The results indicated that the proposed method is accurate and reliable. This method is a modification of the QuEChERS method, and is advantageous owing to its simplicity and high sensitivity. The use of matrix-matching calibration curves and internal standards can eliminate matrix interference, thereby increasing the accuracy of the method. This method satisfies the testing requirements for chlormequat chloride, thidiazuron, and paclobutrazol residues in animal-derived foods, and is promising for the determination of other PGRs or other types of pesticides in animal-derived foods.

Establishment of import tolerance for the insecticide thiacloprid in strawberry

To promote exports, import tolerance (IT) of thiacloprid in strawberry was proposed using the Organization for Economic Cooperation and Development (OECD) maximum residue limit (MRL) calculator after conducting three different field trials. The pre-harvest interval of residual pattern and degradation dynamics of thiacloprid in strawberry were determined using ultra-performance liquid chromatography-tandem mass spectrometry. Samples were extracted with acetonitrile and a mixture of salts and dilution was performed for purification. A six-point matrix-matched calibration curve was constructed which provided excellent linearity with coefficient of determination (R² ) of 0.9998 or more. Detection and quantification limits were 0.003 and 0.01 mg/kg, respectively. The method was validated in quintuplicate at three different concentrations, which resulted in acceptable recovery ranging from 80.86% to 101.71% with relative standard deviation of 6.50 or less among the three field sites. The developed method was applied to the field-treated sample harvested at different intervals. In the pre-harvest interval trial, the amount of thiacloprid residues ranged from 0.24 to 0.70 mg/kg in field site 1 (Nonsan), 0.16 to 0.50 mg/kg in field site 2 (Sunchang), and 0.36 to 0.50 mg/kg in field site 3 (Sacheon). By contrast, in the degradation trial, the observed residues were 0.03-0.81 mg/kg in field site 1 and 0.02-0.48 mg/kg in field site 2. Consequently, the IT of thiacloprid in strawberry using the OECD MRL calculator was proposed as 2 mg/kg, which is exactly the same as the MRL established by the Republic of Korea. In conclusion, the residue study proposes 2.0 mg/kg as the MRL of thiacloprid in strawberries.

Screening of multiclass pesticide residues in maca and Moringa oleifera by a modified QuEChERS sample preparation procedure and UPLC-ESI-MS/MS analysis

In the present study, a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was proposed for the simultaneous analysis of 75 pesticides in maca and Moringa oleifera with ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). The developed method was validated in accordance with linearity, linear range, limit of detection, limit of quantification, accuracy, precision, and matrix effect. Each analyte had good linearity (R² > 0.99) in the corresponding concentration range. The method LOD and LOQ values of all the analytes ranged from 0.01 μg kg⁻¹ to 303.35 μg kg⁻¹ and 0.03 μg kg⁻¹ to 1011.15 μg kg⁻¹, respectively. The recoveries (n = 6) of the analyzed pesticides were in the range of 75.92–113.43%. The RSDs of precision were between 0.60% and 7.36%. All matrix effect values ranged from 81.79% to 118.71% and 80.36% to 119.64% in maca and Moringa oleifera, respectively. The analysis of 103 samples showed the presence of isofenphos-methyl in some of them. The method had a good application prospect and could be used as a general approach for the quantitative determination of pesticide residues in food.

In the present study, a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was proposed for the simultaneous analysis of 75 pesticides in maca and Moringa oleifera with UPLC-ESI-MS/MS.