Determination of the phenoxyacid herbicides MCPA, mecoprop and 2,4-D in kidney tissue using liquid chromatography with electrospray tandem mass spectrometry

Animal Pesticide Poisoning in Tunisia

During the period from 2014 to 2017, a retrospective study on pesticide poisoning in domestic animals and livestock was compiled and then analyzed. A total of 71 pesticide analyses have been submitted to the Pharmacy and Toxicology Laboratory of the School of Veterinary Medicine of Sidi Thabet in Tunisia. All the cases were first referred either through the clinical and/or pathological departments of the Veterinary School, the private and/or governmental veterinarians or directly by the pet owners. Among the total number of the suspected samples, 21 (29.6%) cases were found positive for various kinds of pesticides. Carbamate insecticides were the most frequently implicated pesticide (52.4% of the total positive cases), followed by organophosphate insecticides (19%), then rodenticides-anticoagulants and rodenticides non-anticoagulants (14.3% each). Therefore, carbamates and organophosphates are the most implicated group of pesticides in intoxications (71.4%). Among the 21 positive cases were 11 dogs, 4 cats, 3 poultry, 2 ruminants, and 1 case of bee poisoning. Partition chromatography (HPLC) has been used to characterize the incriminated pesticides. The aim of this survey was to determine incidence and characteristics of pesticide poisoning in domestic and farm animals in Tunisia. The reported results are useful for epidemiological cartography and medical management of intoxicated animals.

Deposition of CdTe quantum dots on microfluidic paper chips for rapid fluorescence detection of pesticide 2,4-D

Rapid detection of pesticides in fruits is an ongoing challenge. The objective of the present study was to develop novel fluorescent microfluidic paper chips for specific recognition and sensitive detection of the pesticide 2,4-D through the electron-transfer-induced fluorescence quenching mechanism. CdTe quantum dots (QDs) were deposited onto cellulose paper (base material) to yield imprinted paper chips (paper@QDs@MIPs). This method allows the transferability of the molecularly imprinted fluorescence sensor from the liquid phase to the solid phase (paper base) for rapid and portable analysis. The resultant imprinted paper chips were effectively characterized, and they exhibited ideal ordered spatial network structure, chemical stability, and fluorescence property. The paper@QDs@MIPs showed that 2,4-D binding significantly reduced the fluorescence intensity within less than 18 min, and it achieved satisfactory linearity in the range of 0.83-100 μM and high detectability of 90 nM. The recognition specificity for 2,4-D relative to its analogues was shown, and the imprinting factor was 2.13. In addition, the recoveries of the spiked bean sprouts at three concentration levels ranged within 94.2-107.0%, with a relative standard deviation of less than 5.9%. Collectively, the device provided an effective platform for rapid recognition, convenience, and detection of trace food pollutants in complex matrices, thereby ensuring food safety and further promoting surface imprinting studies.

Preparation and Characterization of Herbicide Mecoprop Imprinted Polymer and Its Application as a Selective Sorbent in Water Sample

Bulk polymerization method was used to prepare a homogeneous molecularly imprinted polymer (MIP) for the specific extraction of herbicide mecoprop (MCPP). Thereafter, the binding performance of this functional polymer was evaluated under optimal condition, compared to a non-imprinted polymer. From the Scatchard plot analysis, two types of binding sites were detected in the MIP, the high affinity binding sites with a K_D (equilibrium dissociation constant) of 6.4 µM and the low affinity ones with a K_D of 55.9 µM. In addition, the possibility of using synthesized MIP for MCPP extraction from environmental aqueous samples was explored. The adsorption capacity of MIP in spiked bottled water and groundwater samples showed that the polymer could effectively extract MCPP from bottled water and groundwater (p < 0.05) with the recovery of 70.5% and 65.1%, respectively, demonstrating the potential of imprinted polymers for cost-effective and effective water treatment.

Determination of Acid Herbicides Using Modified QuEChERS with Fast Switching ESI(+)/ESI(-) LC-MS/MS

A method for the determination of 35 acid herbicides in food matrices was developed, validated, and implemented. It utilizes a modified QuEChERS extraction procedure coupled with quantitation by liquid chromatography tandem mass spectrometry (LC-MS/MS). The acid herbicides analyzed are all organic carboxylic acids, including the older chlorophenoxy acid herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D), dicamba, 4-chlorophenoxyacetic acid (4-CPA), quinclorac, and many of the newer imidazolinone herbicides such as imazethapyr and imazaquin. In the procedure, 10 mL of water is added to 5 g of sample and then extracted with 1% formic acid in acetonitrile for 1 min. The acetonitrile phase is salted out of the extract by adding sodium chloride and magnesium sulfate, followed by centrifugation. The acetonitrile is diluted 1:1 with water to enable quantitation by LC-MS/MS using fast switching between positive and negative electrospray ionization modes. The average recoveries for all the compounds except aminocyclopyrachlor were 95% with a precision of 8%. The method detection limits for all residues were less than 10 ng/g, and the correlation coefficients for the calibration curves was greater than 0.99 for all but two compounds tested. The method was used successfully for the quantitation of acid herbicides in the FDA's total diet study. The procedure proved to be accurate, precise, linear, sensitive, and rugged.

Dissipation and residue of 2,4-D in citrus under field condition

The dissipation, residues, and risks of 2,4-dicholrophenoxyacetic acid (2,4-D) in citrus under field condition were investigated based on a simple ultra-performance LC (UPLC)-MS/MS method. The results indicated that the residue level of 2,4-D in citrus did not degrade gradually with sampling time under field condition. At pre-harvest intervals (PHI) of 20-40 days, 2,4-D residues were 0.021-0.269 mg/kg in citrus flesh, 0.028-0.337 mg/kg in whole citrus, and 0.028-0.376 mg/kg in citrus peel, all bellow the China maximum residue limit in citrus (1 mg/kg). Risks of 2,4-D were assessed by calculation of risk quotient, and the results revealed no significant health risks after consumption of citrus.

Simultaneous determination of acidic pesticides in vegetables and fruits by liquid chromatography--tandem mass spectrometry

A sensitive and efficient method has been developed for the simultaneous determination of 73 multi-class acidic pesticides, such as phenoxy acid and sulfonylurea herbicides, in vegetables and fruits. The sample preparation procedure was carefully optimized for the efficient removal of co-extracted matrix components. The method involves extraction of acidic pesticides with acetonitrile containing hydrochloric acid, removal of water from crude extract by salting out, and sequential cleanup by octadecylsilyl silica gel and silica gel columns. For samples containing high amounts of pigments, such as spinach, additional cleanup using a graphitized carbon column was performed prior to liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Recovery tests were performed for five times for each sample of cabbage, spinach, potato, eggplant, orange, and apple fortified at 0.01 mg kg-1. Out of the 73 tested pesticides, 70 for cabbage, 67 for spinach, 69 for potato, 67 for eggplant, 64 for orange, and 70 for apple were within the range of 70-120%, with relative standard deviations below 25%. Nitenpyram and pyrasulfotole showed low recoveries for all the samples tested, probably due to low recoveries from silica gel column. The developed method effectively removed co-extracted matrix components and was highly selective, with no interfering peaks found in the chromatograms of blank samples. The overall results indicate that the developed method is suitable for the quantitative analysis of acidic pesticide residues in vegetables and fruits.

Liquid chromatographic determination of endogenous phytohormones in vegetable samples based on chemical derivatization with 6-oxy(acetylpiperazine) fluorescein

In phytohormone analysis, mass spectrometry (MS)-based methods are primary and powerful tools. However, complex sample preparation and high cost are problems for their application. As a complement for MS-based methods, a new fluorescent labeling reagent for carboxylic acids, 6-oxy(acetylpiperazine) fluorescein (APF), has been used for the determination of endogenous phytohormones, including indolebutyric acid, 1-naphthaleneacetic acid and 2,4-dichlorophenoxyacetic acid. The derivatization yield was maximized by optimizing derivatization conditions in detail, and the derivatives of three phytohormones could be separated completely in 15 min on a C18 column with fluorescence detection at lambda(ex)/lambda(em) = 467/512 nm. The derivatization limits could reach 0.1 microM, and the detection limits (signal-to-noise ratio = 3) were 4.43-14.2 nM. The proposed method has been applied to the determination of the exogenous phytohormones in the crude extracts of vegetable samples without extra purification and enrichment with recoveries of 94.2-102.4%.