Toxicity Tests for Chemical Pesticide Registration: Requirement Differences among the United States, the European Union, Japan, and China?

Pesticide registration is a scientific, legal, and administrative process that checks if a pesticide is safe and effective for its intended use before it can be used. The toxicity test is a key part of pesticide registration, which includes human health and ecological effect testing. Different countries adopt their own toxicity test criteria for pesticide registration guidelines. However, these differences, which may help accelerate the progress of pesticide registration and reduce the number of animals used, are yet to be explored and compared. Herein, we outlined the details and compared the differences between the toxicity tests in the United States, the European Union, Japan, and China. Some differences lie in the types and waiver policy, while others are in new approach methodologies (NAMs). On the basis of these differences, there is great potential for the optimization of NAMs during the toxicity tests. It is expected that this perspective can contribute to developing and adopting NAMs.

Analytical method for the determination of meptyldinocap as the 2,4-dinitro-octylphenol metabolite in cucumber and soil using LC-MS/MS and a study of the residues in a Chinese cucumber field ecosystem.

BACKGROUND: Meptyldinocap (2,4-DNOPC) is a novel powdery mildew (Erysiphe necator) fungicide which shows protectant and post-infective activities. However, there is no reliable validated LC-MS/MS method for measuring trace levels of meptyldinocap in cucumber. A method for the determination of 2,4-DNOPC using LC-MS/MS in cucumber and soil was developed. Additionally, the mode of degradation and the residue levels in cucumbers and soils were investigated. RESULTS: Recoveries of meptyldinocap from cucumber and soil samples were found to be 81.4-95.1%. The limits of quantification were found to be 0.01 mg kg(-1) in cucumber and soil. The half-lives of metpyldinocap in cucumbers and soils were in the ranges of 1.6 to 2.2 days and 3.1 to 4.4 days. The harvest residue levels of meptyldinocap in cucumbers and soils were in the ranges of below 0.01 mg kg(-1) to 0.92 mg kg(-1) , and below 0.01 mg kg(-1) to 0.53 mg kg(-1) . 5 days after application; the harvest residue levels of meptyldinocap in cucumbers in all treatments were below 0.1 mg kg(-1) . CONCLUSION: Compared with the MRL for meptyldinocap in cucumber (0.1 mg kg(-1) ), set by the EU, it is suggested that there should be a pre-harvest interval of 5 days at the recommended rate and times before harvest of cucumber.

Simultaneous determination of five pyrazole fungicides in cereals, vegetables and fruits using liquid chromatography/tandem mass spectrometry.

The sensitive analytical method using quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure for simultaneous determination of five novel pyrazole fungicides residues in cereals (rice and wheat), vegetables (cucumber, tomato, and lettuce), and fruits (apple and grape) was developed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The five pyrazole fungicides (bixafen, fluxapyroxad, furametpyr, pyraclostrobin, and rabenzazole) were extracted from seven matrices using acetonitrile and subsequently cleaned up by octadecylsilane (C(18)) or graphitized carbon black (GCB) prior to LC-MS/MS analysis. The determination of the target compounds was achieved in less than 3.0min using an electrospray ionization source in positive mode (ESI+) for furametpyr, pyraclostrobin, and rabenzazole, while negative mode (ESI-) for bixafen and fluxapyroxad. The method showed excellent linearity (at least R(2)≥ 0.990) for all studied analytes. The limits of detection were below 3.0 µg kg(-1), and the limits of quantification did not exceed 9 µg kg(-1) in all matrices. The overall average recoveries in rice, wheat, cucumber, tomato, lettuce, apple, and grape at three levels (10, 100 and 1,000 µg kg(-1)) were ranged from 70.0% to 108% with all RSDs values less than 20.9% for all analytes. The method is demonstrated to be convenient and reliable for the routine monitoring of pyrazole fungicides in cereals, vegetables and fruits.

Dissipation and residues of flutriafol in wheat and soil under field conditions.

A simple, sensitive method for the analysis of flutriafol in wheat and soil was developed using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The dissipation dynamics and ultimate residue of flutriafol in wheat and soil were detected using the established method. The half-lives of flutriafol in wheat plant were 4.09 days (Hebei) and 1.54 days (Hubei), while in soil were 6.25 days (Hebei) and 3.16 days (Hubei), respectively. The final residues of flutriafol were below 0.5 mg/kg (MRL of EU) in wheat grain 28 days after the treatment.

Development of a method for the analysis of four plant growth regulators (PGRs) residues in soybean sprouts and mung bean sprouts by liquid chromatography-tandem mass spectrometry.

A method has been developed for the simultaneous determination of four plant growth regulators (PGRs) residues in soybean sprouts and mung bean sprouts. The sample preparation procedure was based on a QuEChERS method. The method showed excellent linearity (r(2) ≥ 0.9985) and precision (RSDs ≤ 13.0%). Average recoveries of four PGRs ranged between 74.9% and 106.3% at spiking levels 0.05, 0.5 and 1 mg kg(-1). The LODs and LOQs were in the ranges of 0.27-9.3 µg kg(-1) and 0.90-31 µg kg(-1), respectively. The procedure was applied to 18 bean sprout samples, and benzyladenine was found in some of the analyzed samples.

[Determination of thiophanate-methyl and carbendazim in cucumber and soil by QuEChERS-high performance liquid chromatography-triple quadrupole tandem mass spectrometry].

A method was developed for the determination of thiophanate-methyl and carbendazim residues in cucumber and soil by using QuEChERS-high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The residues in the samples were extracted by acetonitrile, cleaned up by developed QuEChERS method, and then analyzed by using LC-MS/MS in multiple reaction monitoring (MRM) mode via positive electrospray ionization with an Agilent ZORBAX SB-C, column (30 mm x 2.1 mm, 5 microm) as the analytical column. The recoveries of thiophanate-methyl spiked at four levels of 0.01, 0.05, 0.1 and 1.0 mg/kg were from 87.3% to 96.0% with the relative standard deviations (RSDs) of 8.0%-9.3% in cucumber, from 88.8% to 93.4% with the RSDs of 5.3%-9.9% in soil; the recoveries of carbendazim spiked at the same levels as those of thiophanate-methyl were from 87.1% to 92.3% with the RSDs of 5.2%-7.5% in cucumber, from 85.8% to 90.9% with the RSDs of 5.3%-13.2% in soil. The method is simple, rapid and characterized with acceptable sensitivity and accuracy to meet the requirements of the pesticide residue analysis. This method is applicable to confirm the residues of thiophanate-methyl and carbendazim

Enantioselective determination of triazole fungice tetraconazole by chiral high-performance liquid chromatography and its application to pharmacokinetic study in cucumber, muskmelon, and soils.

A simple chiral high-performance liquid chromatography method with diode array detector was developed and validated for stereoselective determination of tetraconazole enantiomers in cucumber, muskmelon, and soils. Good separation was achieved at 20°C using cellulose tris-(4-methylbenzoate) as chiral stationary phase, a mixture of n-hexane and ethanol (90:10) as mobile phase at a flow rate of 0.8 ml/min. The assay method was linear over a range of concentrations (0.5-50 µg/ml) and the mean recoveries in all samples were more than 85% for the two enantiomers. The limits of detection for both enantiomers in plant and soil samples were 0.06 and 0.12 µg/g, respectively. Then, the proposed method was successfully applied to the study of enantioselective degradation of rac-tetraconazole in cucumber, muskmelon, and soils. The results showed that the degradation of two enantiomers of tetraconazole followed first-order kinetics and significantly stereoselective behavior was observed in cucumber, muskmelon, and Beijing soil. The preferential absorption and degradation of (-)-S-tetraconzole resulted in an enrichment of the (+)-R-tetraconazole residue in plant samples, whereas the (+)-R-tetraconazole showed a faster degradation in Beijing soil and the stereoselectivity might be caused by microorganisms. No stereoselective degradation was observed in Heilongjiang soil.

Determination of cyantraniliprole and its major metabolite residues in vegetable and soil using ultra-performance liquid chromatography/tandem mass spectrometry.

A rapid, highly sensitive and selective method was developed for the determination of the cyantraniliprole and its major metabolite J9Z38 in cucumber, tomato and soil by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Target compounds were extracted with acetonitrile and an aliquot cleaned with primary and secondary amine. Two pairs of precursor product ion transitions for cyantraniliprole and J9Z38 were measured and evaluated. Average recoveries for cucumber, tomato and soil at three levels (10, 50 and 100 µg/kg) ranged from 74.7 to 96.2% with intra-day relative standard deviation (RSD) of 2.6-15.1% and inter-day RSD of 3.4-13.3%. The limit of quantitation for cyantraniliprole and J9Z38 were determined to be 5 and 10 µg/kg in samples (cucumber, tomato and soil), respectively. This method was used to determine the cyantraniliprole and J9Z38 residues in real cucumber, tomato and soil samples for studies on their dissipation. The trial results showed that the half-lives of cyantraniliprole obtained after treatments were 2.2, 2.8 and 9.5 days in cucumber, tomato and soil in Zhejiang, respectively, and that the average levels of cyantraniliprole and J9Z38 residues in cucumber and tomato were all <0.01 mg/kg with the interval of 10 days after treatment.

[Determination of meptyldinocap residues in vegetable and fruit by liquid chromatography-tandem mass spectrometry].

A method was developed for the determination of the residues of meptyldinocap (2,4-dinitro-6-(1-methylheptyl) phenyl crotonate, 2,4-DNOPC) as 2, 4-dinitrooctylphenol (2,4-dinitro-6-(1-methylheptyl) phenol, 2,4-DNOP), which is a hydrolysate of 2,4-DNOPC, in six vegetable and fruit by using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The residues of 2,4-DNOPC in vegetable and fruit samples were extracted by the mixture of acetone, methanol and hydrochloric acid, then extracted by liquid-liquid partitioning, hydrolyzed under alkaline condition with ultrasonication, and extracted again by liquid-liquid partitioning, then analyzed by using LC-MS/MS in multiple reaction monitoring (MRM) mode via negative electrospray ionization with an Agilent ZORBAX SB-C, column. The method was validated at four fortification levels in vegetable and fruit. The validation results were as follows: the recoveries of 2,4-DNOPC in cabbages were from 89.7% to 93.3% (the relative standard deviations (RSD) of 6. 3% - 8.5%), in cucumbers from 87.7% to 95.1% (RSD of 5.8% -10.4%), in tomatoes from 89.3% to 96.0% (RSD of 6.8% -9.2%), in apples from 92.0% to 98.3% (RSD of 5.1% - 10.3%), in pears from 89.0% to 95.0% (RSD of 5.3% -10.2%), in grapes from 81.2% to 95.8% (RSD of 5.8% - 10.4%). The limits of quantification of 2,4-DNOPC in all the test samples were 0. 01 mg/kg. The results showed that the method is simple, rapid, and is characterized with acceptable sensitivity and accuracy to meet the requirements of the pesticide residue analysis. This method is applicable to confirm the residues of meptyldinocap in vegetable and fruit samples.

Enantioselective determination of triazole fungicide simeconazole in vegetables, fruits, and cereals using modified QuEChERS (quick, easy, cheap, effective, rugged and safe) coupled to gas chromatography/tandem mass spectrometry.

A rapid and effective method for enantioselective determination of simeconazole enantiomers in food products (cucumber, tomato, apple, pear, wheat and rice) has been developed. The enantiomers were resolved by capillary gas chromatography (GC) using a commercial chiral column (BGB-172) and a temperature program from 150°C (held for 1 min) and then raised at 10°C min(-1) to 240°C (held for 10 min). This enantioselective gas chromatographic separation was combined with a clean-up/enrichment procedure based on the modification of QuEChERS (quick, easy, cheap, effective, rugged and safe) method. Co-extractives were removed with graphitized carbon black/primary secondary amine (GCB/PSA) solid-phase extraction (SPE) cartridges using acetonitrile:toluene (3:1, v/v) as eluent. Gas chromatography/ion trap mass spectrometry (GC-ITMS) with electron ionization (EI) was then used for qualitative and quantitative determination of the simeconazole enantiomers. Two precursor-to-product ion transitions (m/z 121-101 and 195-153) with the best signal intensity were chosen to build the multiple-reaction monitoring (MRM) acquisition method. The limits of detection for each enantiomer of simeconazole in six food products ranged between 0.4 and 0.9 µg kg(-1), which were much lower than maximum residue levels (MRLs) established by Japan. The methodology was successfully applied for the enantioselective analysis of simeconazole enantiomers in real samples, indicating its efficacy in investigating the environmental stereochemistry of simeconazole in food matrix.

Dissipation and residues detection of dioctyldiethylenetriamine cetate in rice plant and environment by QuEChERS method and liquid chromatography/electrospray tandem mass spectrometry.

Dioctyldiethylenetriamine acetate (Chinese common name: Xinjunan) is an effective bactericide and virucide widely used on many crops including vegetables and fruits in China. In this study, the dissipation of dioctyldiethylenetriamine acetate 1.8% (w/w) aqueous solution (AS) in rice, soil and water was studied. The result in the supervised field trials showed that the half-lives of dioctyldiethylenetriamine acetate in soil and rice plant were in the range 3.9-6.6 and 6.2-12 days, respectively. It also indicated that the decline followed first-order kinetics. The dissipation of Xinjunan in water, was stimulated in a laboratory container, showed that it could rapidly deposit on solid particles and might form bound residues in surface levels of soil. According to the toxicological data and the dietary intake of rice, a MRL (Maximum Residue Limits) of 0.1 mg/kg for dioctyldiethylenetriamine acetate in the rice was recommended for national accessment. The results indicated that the supervised trials median residues (STMR) is 0.02 mg/kg and only 0.2% of the acceptable daily intake (ADI) is occupied by dietary daily intake in the average Chinese population. It would be unlikely to pose any public health issues if dioctyldiethylenetriamine acetate was applied according to the use pattern suggested by the manufactures on the label.

Determination of the volatile composition in essential oil of Descurainia sophia (L.) Webb ex Prantl (Flixweed) by gas chromatography/mass spectrometry (GC/MS).

Exhaustive hydro-distillation of Descurainia sophia (L.) Webb ex Prantl (flixweed) collected from two different locations (Cangzhou city-Sample 1 and Beijing city-Sample 2) gave in both cases yellowish colored oils in 0.31 and 0.26% yield, respectively. Detailed chemical composition of the essential oils was analyzed by GC and GC/MS, and forty and thirty-eight compounds were identified. The results indicated that the most abundant component of Sample 1were cis-beta-ocimene (20.1%), menthol (11.27%), neoisomenthyl acetate (3.5%), alloaromadendrene (2.28%) and longicyclene (2.25%). Compared with the constituents of Sample 1, several chemical compounds such as 1,8-cineole, alpha-eudesmol, cis, trans-farnesol and beta-pinene were not detected in Sample 2 although it was similarly dominated by cis-beta-ocimene (17.12%), menthol (10.7%) and neoisomenthyl acetate (2.96%). Final analysis of the chemical constituents in the essential oils of the two samples showed similarity in their chemical composition, but the relative content of all shared chemical constituents in Sample 2 was lower than that in Sample 1.

Chiral separations of pesticide enantiomers by high-performance liquid chromatography using cellulose triphenylcarbamate chiral stationary phase.

The direct chiral separations of pesticide enantiomers by high-performance liquid chromatography by applying self-prepared cellulose triphenylcarbamate chiral stationary phase are performed. The mobile phase is n-hexane modified by isopropanol as a polar modifier. Nine chiral pesticides (benalaxyl, vinclozolin, diclofop-methyl, tebuconazole, quizalofop-ethyl, hexaconazole, lactofen, isocarbophos, and paclobutrazol) show enantioselectivity on the chiral stationary phase. An online circular dichrorism detector is used for identifying the pesticide enantiomers. The influences of the volume content of isopropanol and column temperature on the separations are investigated. The thermodynamic parameters related to the chiral distinguish mechanisms are also calculated.