Determination of Triazole Fungicide Residues in Fruits by QuEChERS Combined with Ionic Liquid-Based Dispersive Liquid-Liquid Microextraction: Optimization Using Response Surface Methodology

Dissipation and Safety Analysis of Dimethomorph Application in Lychee by High-Performance Liquid Chromatography-Tandem Mass Spectrometry with QuEChERS

This study presents a method for analyzing dimethomorph residues in lychee using QuEChERS extraction and HPLC-MS/MS. The validation parameters for this method, which include accuracy, precision, linearity, and recovery, indicate that it meets standard validation requirements. Following first-order kinetics, the dissipation dynamic of dimethomorph in lychee was determined to range from 6.4 to 9.2 days. Analysis of terminal residues revealed that residues in whole lychee were substantially greater than those in the pulp, indicating that dimethomorph residues are predominantly concentrated in the peel. When applied twice and thrice at two dosage levels with pre-harvest intervals (PHIs) of 5, 7, and 10 days, the terminal residues in whole lychee ranged from 0.092 to 1.99 mg/kg. The terminal residues of the pulp ranged from 0.01 to 0.18 mg/kg, with the residue ratio of whole lychee to pulp consistently exceeding one. The risk quotient (RQ) for dimethomorph, even at the recommended dosage, was less than one, indicating that the potential for damage was negligible. This study contributes to the establishment of maximum residue limits (MRLs) in China by providing essential information on the safe application of dimethomorph in lychee orchards.

Simultaneous determination of triazole fungicides in animal-origin food by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry

A method for the simultaneous determination of 21 triazole fungicides in animal-origin foods was established by using UPLC-MS/MS. The dilution solvent, extraction solvent, and QuEChERS purification adsorbent composition, were optimized. The response value of the target compound was the highest and the chromatographic peak shape was optimal under the following conditions: water-acetonitrile as the mobile phase, acetonitrile to extract the target compound, C18 (100 mg) as the adsorbent, and water-acetonitrile as the diluent. Our method was validated under electrospray ionization (ESI) + conditions with six animal-origin foods. The 21 triazole fungicides showed good linear relationships (0.1-20 μg∙L-1, R2 > 0.99). The limits of detection and quantitation ranged from 0.1 to 0.3 μg∙kg-1 and 0.3 to 0.9 μg∙kg-1, respectively. The average recoveries ranged from 72.0% to 114.8% with RSDs < 9.9%. Therefore, our method was suitable for the determination of pesticide residues in commercially available animal-origin samples.

Dispersive magnetic solid phase extraction of triazole fungicides based on polybenzidine/magnetic nanoparticles in environmental samples

A polybenzidine-modified Fe3O4@SiO2 nanocomposite was successfully synthesized through a chemical oxidation method and employed as a novel sorbent in dispersive magnetic solid phase extraction (DMSPE) for the preconcentration and determination of three triazole fungicides (TFs), namely diniconazole, tebuconazole, and triticonazole in river water, rice paddy soil, and grape samples. The synthesis method involved a polybenzidine self-assembly coating on Fe3O4@SiO2 magnetic composite. Characterization techniques such as FT-IR, XRD, FESEM, EDX, and VSM were used to confirm the correctness of the synthesized nano-sorbent. The target TFs were determined in actual samples using the synthesized nanocomposite sorbent in combination with gas chromatography-flame ionization detection (FID). Several variables were carefully optimized , including the sample pH, sorbent dosage, extraction time, ionic strength, and desorption condition (solvent type, volume, and time). Under the optimized experimental conditions, the method exhibited linearity in the concentration range 5-1000 ng mL-1 for triticonazole and 2-1000 ng mL-1 for diniconazole and tebuconazole. The limits of detection (LOD) for the three TFs were in the range 0.6-1.5 ng mL-1. The method demonstrated acceptable precision with intra-day and inter-day relative standard deviation (RSD) values of less than 6.5%. The enrichment factors ranged from 248 to 254. Finally, the method applicability was evaluated by determining TFs in river water, rice paddy soil, and grape samples with recoveries in the range 90.5-106, indicating that the matrix effect was negligible in the proposed DMSPE procedure.

Mechanism analysis and improved molecular modification: Design of high efficiency and environmentally friendly triazole fungicide substitutes

The adverse effects of triazole fungicides (TFs) on the soil and the environmental damage caused by their residues have attracted the attention of the international community. To effectively prevent and control the above problems, this paper designed 72 substitutes of TFs with significantly better molecular functionality (>40%) using Paclobutrazol (PBZ) as the template molecule. Then, the comprehensive scores for environmental effects calculated after normalization by "extreme value method-entropy weight method-weighted average method" was the dependent variable, the structural parameters of TFs molecules was the independent variable (PBZ-214 was the template molecule) to construct the 3D-QSAR model of integrated environmental effects of TFs with high degradability, low bioenrichment, low endocrine disruption effects, and low hepatotoxicity and designed 46 substitutes of TFs with significantly better comprehensive environmental effects (>20%). After confirming the above effects of TFs and assessing human health risk and the universality of biodegradation and endocrine disruption, we screened PBZ-319-175 as the eco-friendly substitute of TF, which had high efficiency (improved functionality) and better environmental effects than those of the target molecule by 51.63% and 36.09%, respectively. Finally, the results of the molecular docking analysis showed that non-bonding interactions (hydrogen bonding, electrostatic, or polar force) predominantly affected the association between PBZ-319-175 and its biodegradable protein, and the hydrophobic effect of the amino acids distributed around PBZ-319-175 played a significant role. Additionally, we determined the microbial degradation path of PBZ-319-175 and found that the steric hindrance of the substituent group after molecular modification promoted its biodegradability. In this study, we enhanced molecular functionality twice and also reduce the major damage of TFs to the environment by performing iterative modifications. This paper provided theoretical support for the development and application of high-performance, eco-friendly substitutes of TFs.

Combination of switchable hydrophilic solvent liquid-liquid microextraction with QuEChERS for trace determination of triazole fungicide pesticides by GC-MS

This work first proposed a novel green and efficient method based on Quick, Easy, Cheap, Efficient, Rugged, and Safe pretreatment (QuEChERS) combined with switchable hydrophilic solvent homogeneous liquid-liquid microextraction (SHS-HLLME) for trace determination of triazole fungicides (TFs) in agricultural products such as vegetables and fruits by gas chromatography-mass spectrometry (GC-MS). N,N-Dimethyl benzylamine was used for the synthesis of SHS. Box-Behnken design was applied for the optimization of extraction conditions and a mathematical model was obtained. Ultimately, 0.50 mL SHS, 1.0 mL 10 mol L^-1 sodium hydroxide, and 45 s ultrasonic time were determined as optimal conditions for the SHS-HLLME method. The limit of detection and limit of quantification determined using the optimal method (SHS-HLLME/GC-MS) were 0.13-0.27 ng mL^-1 and 0.43-0.90 ng mL^-1, respectively. In addition, the SHS-HLLME method under optimal conditions was combined with the traditional QuEChERS method to realize the advancement of the SHS-HLLME method from simple to complex matrix analysis, and the QuEChERS-SHS-HLLME method was successfully applied to the analysis of TFs in cucumbers, tomatoes, watermelon and grapes in agricultural products. Matrix-matched calibration standards were used to improve the accuracy of TFs in spiked cucumber samples to obtain recovery results close to 100%. It was shown that the new method is green and rapid, enabling fast and inexpensive sample pretreatment with up to 100-fold enrichment factor and low detection limit compared with the original QuEChERS method.

Study of insecticide translocation in coconut palm trees after using pressurized endotherapy

Alternative techniques for applying agricultural products, such as pressurized endotherapy, have shown promise in pest and disease control in coconut palms (Cocos nucifera Linn.). In this work, azadirachtin and abamectin were applied by pressurized endotherapy to control Brassolis sophorae. Twelve different treatments were carried out, and in all of them, at least one plant had the larvae completely dead four and five days after endotherapeutic applications, and all the others died within the next few hours. Leaf and fruit analyses were performed to determine the concentration over time. High concentrations of abamectin were observed after 15 and 30 days on leaves when applied in larger volumes. In fruits, no residue was found regardless of the applied concentration. Analytical methods were developed and validated for leaves and fruits to analyze insecticide residues using LC-MS/MS and modified QuEChERS acetate according to SANTE/11813/2017 guidelines. The insecticide translocation tests in the leaves and the high mortality of insects showed that pressurized endotherapy is a technique to be considered for future studies in controlling B. sophorae in coconut palm trees.

Simultaneous Determination of Seven Pesticides and Metabolite Residues in Litchi and Longan through High-Performance Liquid Chromatography-Tandem Mass Spectrometry with Modified QuEChERS

This study established a QuEChERS high-performance liquid chromatography/tandem triple-quadrupole mass spectrometry method for determining azoxystrobin, pyraclostrobin, picoxystrobin, difenoconazole, chlorantraniliprole, imidacloprid, and cyantraniliprole and its metabolite (IN-J9Z38) in litchi and longan, and applied this method to the real samples. The residues in samples were extracted with acetonitrile and purified with nano-ZrO2, C18, and PSA. The samples were then detected with multireactive ion monitoring and electrospray ionization in the positive ion mode and quantified using the external matrix-matched standard method. The results showed good linearities for the eight analytes in the range of 1−100 μg/L, with correlation coefficients (r2) of >0.99. The limit of quantification was 1−10 μg/kg, and the limit of detection was 0.3−3 μg/kg. Average recovery from litchi and longan was 81−99%, with the relative standard deviation of 3.5−8.4% at fortified concentrations of 1, 10, and 100 μg/kg. The developed method is simple, rapid, efficient, and sensitive. It allowed the rapid screening, monitoring, and confirming of the aforementioned seven pesticides and a metabolite in litchi and longan.

Development of a method based on dispersive liquid-liquid microextraction followed by partial vaporization of the extract for ultra-preconcentration of some pesticide residues in fruit juices

A new simple and efficient method has been developed for the ultra-preconcentration of multiclass pesticide residues including penconazole, chlorpyrifos, ametryn, clodinafop-propargyl, diniconazole, oxadiazon, and fenpropathrin from some fruit juice samples based on evaporation of the sedimented organic phase obtained from dispersive liquid-liquid microextraction. The enriched target analytes were analyzed by gas chromatography-flame ionization detection. In the microextraction procedure, a mixture of iso-propanol as a disperser and 1,2-dibromoethane as an extraction solvent is quickly injected into an aqueous phase containing the analytes and centrifuged. Afterward, the sedimented phase is transferred into a special shaped vaporization vessel and vaporized with nitrogen gas stream until remaining about 2 µL of it. Eventually, 1 µL of the remained sedimented phase is removed and analyzed by separation system. The optimum extraction and disperser solvents were found to be 1,2-dibromoethane and iso-propanol, respectively. In addition, the optimum pH range was 6-8, and nitrogen gas stream at a flow rate of 90 mL min^-1 in a downward oriented vessel was applied. Eventually, the limits of detection and quantification were obtained in the ranges of 45-78 and 149-261 ng L^-1, respectively. Relative standard deviations at the concentrations of 300, 500 and 1000 ng L^-1 of each analyte were ranged between 2.2% and 5.8% for intra-day (n = 6) precision. Inter-day (n = 3) precision at a concentration of 500 ng L^-1 of each analyte was obtained in the range of 4.9-7.1%. In addition, enrichment factors and extraction recoveries were ranged from 1382-2246 and 55-89%, respectively. Finally, the method was successfully utilized in analysis of the target pesticides in the selected juices.

Sequential extraction and enrichment of pesticide residues in Longan fruit by ultrasonic-assisted aqueous two-phase extraction linked to vortex-assisted dispersive liquid-liquid microextraction prior to high performance liquid chromatography analysis

A simple, green and efficient method for extraction, purification and enrichment of pesticide residues of triazoles and pyrethroids in Longan fruit was developed by ultrasonic-assisted aqueous two-phase extraction (UAATPE) coupled to vortex-assisted dispersive liquid-liquid microextraction (VADLLME). Using an aqueous two-phase system (ATPS) of ethanol/K₂HPO₄ as extraction solvent, the composition of the ATPS, extraction temperature and time were investigated, respectively. Then VADLLME process also was optimized by investigating type and volume of extracting and dispersive solvents, vortex-assisted time and salt addition. The optimum conditions were as follows: the ATPS composition of ethanol concentration 30.0% (w/w) and K₂HPO₄ concentration 25% (w/w), extraction temperature 70 °C and extraction time 15 min for UAATPE; 1-dodecanol 200 μL as extraction solvent, ethanol 1.25 mL as dispersive solvent, vortex-assisted time 1.5 min and addition of NaCl 4% (w/v) for VADLLME. Ethanol as extraction solvent and dispersive solvent could directly connect UAATPE with VADLLME without extra steps. By means of HPLC-DAD detection, nine pesticides had good linearity ranged from 0.0200 to 13.59 μg/mL (R² ≥ 0.9957). LODs and LOQs were in the range of 0.005576-0.01740 μg/mL and 0.01859-0.05010 μg/mL, respectively. UAATPE-VADLLME coupled to HPLC was successfully applied to simultaneous determination of multiple pesticides in Longan fruit, and mean recoveries and RSDs were between 76.95% and 98.63%, 1.2% and 9.8%, respectively. Furthermore, myclobutanil, fenpropathrin and deltamethrin were detected in pericarp and pulp of Longan samples from different districts, respectively.