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A rapid, sensitive and reliable analytical method for thidiazuron residues in apple and soil was established. The residual levels of the pesticide in apple and soil were determined by high performance liquid chromatography (HPLC) with UV detector. Samples of apple and soil were extracted with acetonitrile-water solutions, and then cleaned up by Florisil or C(18) cartridges. The results showed good linearity (r(2)=1.000) over the concentration range of 0.01-5.0 mg/L. Limits of quantification (LOQ) of the method were 0.01 mg/kg for both soil and apple. Recovery from the apple and soil samples were 83.36%-84.08% and 85.27%-89.83%, respectively, and the corresponding relative standard deviations (RSDs) of the recovery data were 0.155%-0.524% and 0.475%-4.79% for the three fortified levels (0.01, 0.1, 0.5 mg/kg). The analyte in the samples were further confirmed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). It was demonstrated that the proposed method was simple and efficient, and particularly suitable for detecting thidiazuron residues in apple and soil.

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Flumorph is an oomycete fungicide that is now used extensively in China (Hu, J. Y.; Liu, C.; Yan, H. Degradation of flumorph in soils, aqueous buffer solutions, and natural waters. J. Agric. Food Chem. 2008, 56, 8574-8579). The photodegradation of flumorph in aqueous solutions and natural water have been assessed under natural and controlled conditions in this work. The kinetics of photodecomposition of flumorph was determined using the high-performance liquid chromatography (HPLC)-diode array detector (DAD), and the identification of photoproducts was carried out with HPLC-mass spectrometry (MS) [electrospray ionization (ESI) positive mode]. The rate of photodecomposition of flumorph in aqueous solutions and natural water followed first-order kinetics in both UV radiation and natural sunlight, and the Z isomer of flumorph could convert to the E isomer. The degradation rates were faster under UV light than sunlight, with the half-lives (t(1/2) = ln 2/k) of 36.5-64.2 min and 36.3-73.1 days, respectively. One major photoproduct was detected in UV light and tentatively identified according to HPLC-MS spectral information as (E or Z)-3-(3, 4-dimethoxyphenyl)-3-(4-fluorophenyl)-2-acrylamide. Photosensitizers, such as H(2)O(2) and riboflavin, could enhance photolysis of flumorph in natural sunlight. The results obtained indicated that photoreaction was an important dissipation pathway of flumorph in natural water systems.

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Flumorph is an oomycete fungicide that is now used extensively in China. A residue analysis method for the determination of flumorph in environmental samples was developed with solid-phase extraction (SPE) for sample preparation and high-performance liquid chromatographic (HPLC) for separation. An environmental fate study was performed concerning the degradation of flumorph in soils, aqueous buffer solutions, and natural waters under laboratory-controlled conditions. The degradation of flumorph in three Chinese soil samples followed a first-order kinetics, with half-lives all longer than 100 days. No degradation of flumorph occurred in aqueous buffer solutions having different pH values or in natural waters with different physical and chemical properties. The data generated from this study could be helpful for risk assessment studies of the pesticide in the environment.

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A method for high-performance liquid chromatographic (HPLC) determination of flumorph residues in cucumber, tomato, soil, and natural water was developed and validated. Primary secondary amine or octadecylsilyl (C18) solid-phase extraction cartridges were used for sample preparation. Reversed-phase HPLC with UV detection was used for separation and quantification of the pesticide. The combined cleanup and chromatographic method steps were sensitive and reliable for simultaneous determination of residues of the 2 isomers of flumorph in the studied samples. This method is characterized by recovery > 97.9%, coefficient of variation < 6.2%, and limit of quantification of 0.01 mg/kg, in agreement with directives for method validation in residue analysis. Flumorph residues in the samples were further confirmed by HPLC/mass spectrometry. The proposed method is fast, easy to perform, and could be used for monitoring of pesticide residues.

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Solid-phase extraction (SPE) procedure for cleanup followed by HPLC-UV method has been investigated for the determination of pyraflufen-ethyl residues in soil. The pesticide is extracted from the sample with acetone-water (80:20, v/v) and the extract is loaded onto an octadecyl (C(18)) column. The pesticide is eluted with acetonitrile and determined by HPLC with a UV detector. Using an acetone-water extraction followed by a C(18) cleanup, this method is characterized by recovery >90.1%, precision <5.8% RSD and sensitivity of 0.01 mg/kg. The proposed method has been successfully employed for the determination of the degradation dynamics of pyraflufen-ethyl in four agricultural soil samples under laboratory conditions.

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The method of residue analysis of kresoxim-methyl and its dissipation rate in cucumber and soil in a greenhouse were studied. Residues of kresoxim-methyl were extracted from cucumber and soil matrices with acetone, purified by liquid-liquid extraction and Florisil cartridges, and then determined by GC with NP-detector. The limit of detection was estimated to be 9 x 10-12 g, and the minimum determination concentration of kresoxim-methyl in the samples was 0.005 mg kg-1. The average recoveries ranged from 89.4 to 100.2% with a coefficient variation between 2.4 and 8.9%. Dissipation study showed that the half-lives of kresoxim-methyl in cucumber were approximately 6.5 days at both the recommended and double the recommended dosage. Half-lives for both the treatments were approximately 8 days in soil. The present study revealed that the residues in cucumber were below the MRL (0.05 mg kg-1, fixed by EU) after 7 days for both treatments.

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A method using solid-phase extraction for cleanup, followed by high-performance liquid chromatography with ultraviolet detection (HPLC/UV), was developed for the determination of forchlorfenuron residues in watermelon. The pesticide is extracted from the sample with acidic acetonitrile, and the extract is loaded onto a primary-secondary amine (PSA) column. The pesticide is eluted with acetone and determined by HPLC/UV. The PSA column was found to provide effective cleanup, removing the greatest number of sample matrix interferences. The acetonitrile extraction followed by the PSA cleanup provided recoveries of >95%, coefficients of variation (precision) of <10%, and sensitivity of 0.005 mg/kg, in agreement with the directives for method validation in residue analysis. The proposed method was successfully used to determine forchlorfenuron residue levels and dissipation rates in watermelon grown in an experimental greenhouse in Beijing, People's Republic of China.

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The method of residue analysis of a new synthesized fungicide 2-allylphenol was studied by simulating the active compound structure in Gingko tree (Gingko biloba L.) and its dissipation rate and terminal residue levels in tomato under field condition. Residues of 2-allylphenol were extracted from tomato matrix with acetone, purified by liquid-liquid extraction and Florisil cartrieges, and then determined by HPLC with UV-detector. The minimum detectable amount of 2-allylphenol was 3 x 10(-9) g, the minimum detectable concentration of 2-allylphenol in the samples of tomato were 0.01 mg/kg. The ranges of average recoveries and coefficient variation of the method were 87.7%-90.2% and 1.25%-2.06%, respectively. The dissipation rate and terminal residue levels in tomato were determined with the method described above. The results showed that the half-life of 2-allylphenol in tomato was 6.37 d, and 2-allylphenol declined with 82.6% of the initial deposit remaining in tomato at harvest. The terminal residue levels in tomato were 0.15 mg/kg and 0.20 mg/kg following the recommended doses and time intervals.

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HPL-UV residue analytical method for monosulfuron [N-[(4'-methyl) pyrimidin-2'yl]-2-nitrophenylsulfonyl urea] in soil and wheat was developed. Monosulfuron residues were recovered by solvent extraction, followed by liquid-liquid partition, and C18 cartrige clean-up. Excellent method recoveries ranging from 95%-104% for both fortified soil and wheat grain were obtained with coefficients of variation 1.5%-11.8%. The minimum detectable quantities in soil and wheat were both 4 ng, the limit of detection was 0.02 mg/kg. When monosulfuron was applied according to double dosage of maximum recommended use direction(120 g ai/hm2 of 10% monosulfuron wettable powder sprayed for once during development of wheat) in field studies conducted in Shandong Province and near Beijing, monosulfuron residues was not detected in soil and wheat samples collected 75 d after application. Laboratory soil degradation studies showed that monosulfuron degraded faster in acidic soil and strong alkaline soil than in neutral or weak alkaline soil. Half lives in Jiangxi soil, Shijiazhuang soil, Jiangsu soil and Heilongjiang soil were 41, 48, 87 and 84 d respectively. Monosulfuron residues dissipated rapidly in Shandong and Beijing field test sites with half-lives of less than 14 d.

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