Multiresidue method for the quantitation of 20 pesticides in aquatic products

Optimization of Ferimzone and Tricyclazole Analysis in Rice Straw Using QuEChERS Method and Its Application in UAV-Sprayed Residue Study

Rice straw is used as livestock feed and compost. Ferimzone and tricyclazole, common fungicides for rice blast control, can be found in high concentrations in rice straw after unmanned aerial vehicle (UAV) spraying, potentially affecting livestock and human health through pesticide residues. In this study, an optimized method for the analysis of the two fungicides in rice straw was developed using the improved QuEChERS method. After the optimization of water and solvent volume, extraction conditions including ethyl acetate (EtOAc), acetonitrile (MeCN), a mixed solvent, and MeCN containing 1% acetic acid were compared. Different salts, including unbuffered sodium chloride, citrate, and acetate buffer salts, were compared for partitioning. Among the preparation methods, the MeCN/EtOAc mixture with unbuffered salts showed the highest recovery rates (88.1-97.9%, RSD ≤ 5.1%). To address the severe matrix effect (%ME) of rice straw, which is characterized by low moisture content and cellulose-based complex matrices, samples were purified using 25 mg each of primary-secondary amine (PSA) and octadecylsilane (C18), without pesticide loss. The developed method was validated with a limit of quantification (LOQ) of 0.005 mg/kg for target pesticides, and recovery rates at levels of 0.01, 0.1, and 2 mg/kg met the permissible range (82.3-98.9%, RSD ≤ 8.3%). The %ME ranged from -17.6% to -0.3%, indicating a negligible effect. This optimized method was subsequently applied to residue studies following multi-rotor spraying. Fungicides from all fields and treatment groups during harvest season did not exceed the maximum residue limits (MRLs) for livestock feed. This confirms that UAV spraying can be safely managed without causing excessive residues.

Optimized method development and validation for determining donepezil in rat plasma: A liquid-liquid extraction, LC-MS/MS, and design of experiments approach

Donepezil (DPZ), a piperidine-based reversible cholinesterase inhibitor, finds extensive use in treating Alzheimer's disease (AD). Originally designed as an oral formulation, DPZ encounters drawbacks such as a brief duration of action and reduced treatment effectiveness in elderly patients with memory impairment or difficulty swallowing medications. To address these issues and improve patient compliance, researchers are actively exploring alternative DPZ formulations. Consequently, reliable methods are necessary to quantitate DPZ in biological samples for in vivo assessment. Therefore, we propose an efficient, sensitive, wide-dynamic, and cost-effective method for quantitating DPZ in rat plasma. Our method employs liquid-liquid extraction (LLE) followed by liquid chromatography and tandem mass spectrometry, enabling in vivo evaluation of novel DPZ formulations. Notably, our method requires only 20 μL of rat plasma and employs icopezil as the internal standard-a cost-effective compound with chemical similarity to DPZ. We meticulously optimized LLE conditions, taking into account factor interactions through design of experiments (DOE). Our rapid and straightforward extraction and purification involved using 500 μL of pure methyl tert-butyl ether to extract DPZ from the sample within five minutes. The dynamic range of the method extends from 0.5 ng/mL to 1,000 ng/mL, demonstrating excellent sensitivity and suitability for pharmacokinetic studies across diverse DPZ formulations. Following the FDA guidelines, we rigorously validated the developed method, evaluating selectivity, linearity (with a coefficient of determination ≥0.9999), accuracy (ranging from 96.0% to 109.6%), precision (≤13.9%), matrix effect (92.2% to 103.8%), recovery (98.5% to 106.8%), the lower limit of quantitation (0.5 ng/mL), and stability. Finally, we effectively employed the validated method for the long-term pharmacokinetic assessment of a DPZ formulation. We expect that this approach will make a substantial contribution to the advancement of new DPZ formulations, ultimately benefiting individuals afflicted by AD.

A Robust Method for Simultaneous Determination and Risk Assessment of Multiresidual Pesticides in Fishery Products

In this study, we developed and validated a multiresidue analytical method for the simultaneous detection of 24 pesticides in fishery products. Using the EN15662 extraction method and C18 as the adsorbent for purification, the validation results complied with Codex guidelines, achieving recovery rates between 70% and 120% and relative standard deviation values (%RSD) within 20%, indicating excellent performance. The limit of detection ranged from 0.25 to 0.8 ng/kg, and the limit of quantification was between 3 and 10 ng/g, providing sufficient sensitivity to comply with future regulatory standards. The calibration curves for all 24 pesticides exhibited great linearity (R2 > 0.98), also satisfying the Codex requirements. The matrix effect was less than 30% for some pesticides-within ±20%-indicating minimal interference from impurities. An analysis of 300 fishery samples from nine regions across South Korea detected lufenuron at 10 ng/g in eels; however, the risk assessment was below 0.19%, posing no significant hazard to public health. This newly developed analytical method proved effective for the multi-analysis of pesticide residues in fishery products, offering rapid and reliable monitoring of the import and export safety of fishery products.

Development of an enhanced analytical method utilizing pepper matrix as an analyte protectant for sensitive GC‒MS/MS detection of dimethipin in animal-based food products

Herein, an analytical method using gas chromatography-tandem mass spectrometry (GC‒MS/MS) was devised to detect the presence of the troublesome pesticide dimethipin in various animal-based food products, including chicken, pork, beef, eggs, and milk. The injection port was primed with a matrix derived from pepper leaves that acts as an analyte protectant (AP) to safeguard the target compound from thermal degradation during gas chromatography. The presence of AP resulted in a remarkable limit of quantification of 0.005 mg/kg for dimethipin in five matrices. Three different versions (original, EN, and AOAC) of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method were compared for dimethipin extraction, with a double-layer solid-phase extraction (SPE) cartridge utilized for matrix purification. A seven-point external calibration curve was established for dimethipin in the five matrices, demonstrating excellent linearity with determination coefficients (R2) ≥ 0.998. The developed quantitative method was validated by fortifying each matrix with three different concentrations of standard dimethipin, and the average recovery fell within the acceptable range outlined in the CODEX guidelines (ranging from 88.8% to 110.0%), with a relative standard deviation (RSD) of ≤ 11.97%. This method effectively addresses the challenge of analyzing dimethipin and can therefore be used as a routine monitoring tool for dimethipin across various matrices.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.

Highly-Selective Analytical Strategy for 90 Pesticides and Metabolites Residues in Fish and Shrimp Samples

The analysis of pesticide residues in aquatic products is challenging due to low residue levels and the complex matrix interference. In this study, we developed a simple, fast method for the trace analysis of 90 pesticides and metabolites in aquatic products. The analytes covered a wide polarity range with log Kow (log octanol-water partition coefficient) ranging from -1.2 to 6.37. Grass carp (Ctenopharyngodon idellus) and prawn (Penaeus chinensis) samples were chosen to validate the quantification method. The samples were extracted by 0.2% formic-acetonitrile, cleaned by solid-phase extraction (PRiME HLB), and analyzed by high performance liquid chromatography-tandem mass spectrometry. The results showed good linearities for the analytes and were observed in the range of 0.05-50 μg/L. The recoveries of the method were within 50.4-118.6%, with the relative standard deviations being lower than 20%. The limits of quantifications (LOQs) of the method were in the range of 0.05-5.0 μg/kg, which were superior to values compared with other research. The developed method was applied to detect pesticide residues in prawn samples from eastern coastal areas of China. Three herbicide residues of diuron, prometryn, and atrazine were detected in prawn samples. The method was sensitive and efficient, which is of significance in expanding the screening scope and improving the quantitative analysis efficiency in aquatic products.

Multi-Residue Screening of Pesticides in Aquatic Products Using High-Performance Liquid Chromatography-Tandem High-Resolution Mass Spectrometry

Pesticide residues in aquatic products are of great concern due to the risk of environmental transmission and their extensive use in aquaculture. In our work, a quick screening approach was developed for the qualitative and semi-quantitative screening of 87 pesticide residues in aquatic products. The sample preparation was investigated, including extract solvent, extract methods, buffer salts, lipid removal, cleanup materials and filter membranes for aquatic products. Samples were extracted using a modified QuEChERS procedure, and two clean-up procedures were developed for UHPLC-Q/Orbitrap MS analysis based on the fat content of the aquatic products. The screening detection limits for all studied pesticides were distributed between 1 and 500 μg/kg in the three representative matrices. Seventy-one pesticides could be analyzed with a screening limit between 1 and 25 μg/kg in grass carp and crayfish, sixty-one pesticides could be screened for limits between 1 and 50 μg/kg in crab. The accuracy results showed that recoveries ranged from 50 to 120% for 60, 56 and 52 pesticides at medium-level for grass carp, crayfish and crab, respectively. At high spiking levels, 74, 65 and 59 pesticides were recovered within the range of 50-120% for the three matrices, respectively. The relative standard deviations of most compounds in different matrices were less than 20%. With this method, the local farmed aquatic products were tested for pesticide residues. In these samples, ethoxyquinoline, prometryn and phoxim were frequently detected. The majority of these confirmed compounds did not exceed 2.00 μg/kg. A grass carp with trichlorfon at 4.87 μg/kg and two carps with ethoxyquinoline at 200 µg/kg were detected, indicating the potential dietary risk.

Magnetic polymer particles as a highly efficient and facile cleanup adsorbent for multi-pesticide residues analysis in aquatic products

A novel and efficient sample pretreatment procedure using magnetic particles was exploited for the determination of multi-pesticide residues in aquatic products. The magnetic adsorbent was prepared using divinyl benzene and N-vinyl pyrrolidone as functional monomers modified on the Fe₃O₄ @SiO₂. The obtained magnetic adsorbent, octadecylsilane sorbents, and graphitized carbon black were employed as effective adsorbents to remove matrix interferences in aquatic products, and their dosages were optimized. Satisfactory levels of accuracy and precision were procured under optimum conditions. The method limits of quantification ranged from 0.1 to 2.0 μg/kg. The analytical accuracy of the developed method for the analysis of multi-pesticide residues in freshwater and seafood products was validated. It was found to be suitable for the analysis of multi-pesticide residues in different types of aquatic products. Additionally, the method was successfully applied for the analysis of pesticide residues in fish samples obtained from aquaculture plants located in Zhejiang Province, China. The detected concentrations of pesticides ranged from 0.14 to 0.95 μg/kg. In general, this method shows promising application prospects for the rapid determination of multi-pesticide residues in aquatic products.

Selective magnetic solid-phase extraction of amide herbicides from fish samples coupled with ultra-high-performance liquid chromatography with tandem mass spectrometry

An efficient magnetic dummy template molecularly imprinted polymer nanocomposite was prepared using multi-walled carbon nanotubes as a support and metolachlor deschloro as a dummy template. The obtained nanocomposites were characterized using Fourier transform infrared spectroscopy, vibrating sample magnetometry, scanning electron microscopy, and transmission electron microscopy. The adsorption performance of the obtained nanocomposites was evaluated through binding experiments, including static adsorption, kinetic adsorption, and selective recognition studies. The obtained nanocomposites were successfully applied as selective sorbents for the magnetic solid-phase extraction of seven amide herbicides (alachlor, acetochlor, pretilachlor, butachlor, metolachlor, diethatyl ethyl, and dimethachlor) coupled with liquid chromatography-tandem mass spectrometry from fish samples. Under the optimized conditions, the limit of detection was 0.01-0.1 μg/kg. The obtained recoveries of the amide herbicides from the fish samples were in the range of 88.0 to 102.1% with a relative standard deviation of less than 7.5%. This method, which eliminated the effect of template leakage on qualitative and quantitative analysis was found to be superior to the methods reported in the literature. The results indicated that it could be successfully applied to analyze amide herbicides in fish samples with satisfactory recoveries.

Carbofuran induces increased anxiety-like behaviors in female zebrafish (Danio rerio) through disturbing dopaminergic/norepinephrinergic system

Carbofuran, a carbamate pesticide, is widely used in developing countries to manage insect pests. Studies have found that carbofuran posed potential risks for the neurotransmitter systems of non-target species, we speculated that these disruptive effects on the neurotransmitter systems could trigger anxiety-like behaviors. In this study, female zebrafish were exposed to environmental levels (5, 50, and 500 μg/L) of carbofuran for 48 h to evaluate the effects of carbofuran on anxiety-like behaviors. Results showed that zebrafish exhibited more anxiety-like behaviors which proved by the observed higher bottom trend and more erratic movements in the novel tank after carbofuran treatment. In order to elucidate the underlying molecular mechanisms of carbofuran-induced anxiety-promoting effects, we measured the levels of neurotransmitters, precursors, and major metabolites, along with the level of gene expression and the enzyme activities involved in neurotransmitter synthesis and metabolism. The results demonstrated that acute carbofuran exposure stimulated the mRNA expression and enzyme activity of tyrosine hydroxylase, which sequentially induced the increased levels of dopamine and norepinephrine. Tyrosine hydroxylase inhibitor relieved the anxiety-related changes induced by carbofuran, confirming the overactive tyrosine hydroxylase-mediated accumulation of dopamine and norepinephrine in the brain was one of the main reasons for carbofuran-induced anxiety-like behaviors in the female zebrafish. Overall, our study indicated the environmental health risks of carbamate pesticide in inducing neurobehavioral disorders and provided novel insights into the investigation of the relevant underlying mechanisms.

Toxicity of some aquatic pollutants to fish

Pesticide residues threaten fish that live in rivers. This study investigated the effects of Nemacur, malathion, and diuron on freshwater fish behavior, mortality, acetylcholinesterase (ACHE) activity, liver biomarkers, and residue accumulation. Fish were exposed to individual concentration of Nemacur, malathion, and diuron at 1 mg/L and to binary mixtures in glass aquarium 16 L capacity. Mortality of fish was also investigated at a range of 0.0-1 mg/L of Nemacur and malathion. The biochemical effects of the tested compounds were recorded. The results showed abnormal fish behavior at low concentration (0.1 mg/L) of malathion, high fish mortality at 0.1 mg/L of Nemacur and mixtures with Nemacur, and no mortality with diuron. Mortality increased and became more intense after 48 h rather than after 24 h. Diuron increased the effect of Nemacur and malathion at low concentration. ACHE was inhibited at different percentages in the blood serum and brain homogenate due to exposure to Nemacur, malathion, diuron, and/or a combination of these pesticides. Liver biomarker levels were higher in the blood serum of the treated fish than the control group. The interesting outcome of the study is that Nemacur is several folds more toxic than malathion and diuron. Mixtures showed synergistic effects. The pesticide residues in the fish muscles were less than those in the water. It can be concluded that low concentrations of Nemacur, malathion, and diuron are negatively affecting fish in rivers.

Development, validation and matrix effect of a QuEChERS method for the analysis of organochlorine pesticides in fish tissue

This study aims to develop and validate a method to determine OCPs in fish tissues, minimizing the consumption of sample and reagents, by using a modified QuEChERS along with ultrasound, d-SPE and gas chromatography with an electron capture detector (GC-ECD), refraining the pooling. Different factorial designs were employed to optimize the sample preparation phase. The validation method presented a recovery of around 77.3% and 110.8%, with RSD lower than 13% and the detection limits were between 0.24 and 2.88 μgkg^-1, revealing good sensitiveness and accuracy. The method was satisfactorily applied to the analysis of tissues from different species of fish and OCPs residues were detected. The proposed method was shown effective to determine OCPs low concentrations in fish tissues, using small sample mass (0.5 g), making the sample analyses viable without the need for grouping (pool).