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Khay, Sathya,Abd El-Aty, A. M.,Cho, Soon-Kil,Choi, Jeong-Heui,Mamun, M. I. R.,Goudah, Ayman,Shin, Ho-Chul,Shim, Jae-Han John Wiley Sons, Ltd. 2008 Biomedical chromatography Vol.22 No.6
<P>This study was undertaken to investigate whether an additional column clean-up procedure can affect the accuracy of an analytical method developed for the determination of imidacloprid residues in Chinese cabbage. Thereafter, the residue levels and the degradation rates of imidacloprid were investigated in experimental Chinese cabbage plots after treatment with two different commercial formulations: emulsifiable concentrate (EC) and wettable powder (WP). The analyte was determined using high-performance liquid chromatography–ultraviolet detection (HPLC-UVD) and confirmed by high-performance liquid chromatography–mass spectrometry (HPLC-MS) in the select ion-monitoring mode. The mean recoveries ranged from 75.34 to 98.00% and 96.95 to 100.97%, with relative standard deviations of 0.86–4.14 and 1.22–3.52%, in samples treated with and without additional column clean-up procedures, respectively. The minimum detectable amount of imidacloprid was 4 ng, while the limits of detection and quantitation were 0.2 and 0.5 ppm, respectively. The degradation of pesticide was monitored throughout a period of 13 days under greenhouse conditions. Although the behaviors of the EC and WP formulations appear to be similar, the absolute residue levels obtained with EC and WP treatments differed slightly. When imidacloprid formulations were applied (as foliar treatments) according to the recommended rate, the final residues (13 days post-treatment) in Chinese cabbage were much lower than the maximum residue limit (MRL = 3.5 ppm) established by the Korean Food and Drug Administration. Taken together, our study suggests that the analysis of imidacloprid can be performed without an additional column clean-up procedure, and the decline curve and the residue levels in Chinese cabbage could change if the same active ingredient is used in different formulations. Copyright © 2008 John Wiley & Sons, Ltd.</P>
Khay, Sathya,Abd El-Aty, A. M.,Choi, Jeong-Heui,Shin, Eun-Ho,Shin, Ho-Chul,Kim, Jin-Suk,Chang, Byung-Joon,Lee, Chi-Ho,Shin, Sung-Chul,Jeong, Ji Yoon,Shim, Jae-Han WILEY-VCH Verlag 2009 Journal of Separation Science Vol.32 No.2
<P>The principal goal of this work was to develop an efficient method for the simultaneous determination of four pyrethroid (PYR) insecticides, cyfluthrin, cyhalothrin, cypermethrin, and deltamethrin, in porcine muscle and pasteurized milk using liquid–liquid extraction (LLE). Sample extraction was carried out with and without additional column cleanup procedures, and the final determination was made using GC with electron-capture detector (ECD). The pesticide identity was confirmed using GC-MS in the SIM mode. Since there were minor differences between the extraction procedures, extraction without the additional cleanup procedure was used throughout the work. The method was validated by fortifying blank samples with half, two, and four times the maximum residue limit (MRL) of each PYR. The average recoveries (n = 6) ranged from 83.5 to 99.2% and 82.9 to 109% in porcine muscle and pasteurized milk, respectively. The repeatability of measurements expressed as RSDs, was in the range of 1.7–11.9 and 1.5–10.3% in porcine muscle and pasteurized milk, respectively. The LODs ranged from 3.3 to 9 and 3 to 8.1 ppm, whereas the LOQs ranged from 10 to 27.4 and 9 to 24.6 ppm, in porcine muscle and pasteurized milk, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected pesticides were detected in any of the samples.</P>
Khay, Sathya,EI-Aty, A.M. Abd,Choi, Jeong-Heui,Shim, Jae-Han Korean Society of ToxicologyKorea Environmental Mu 2008 Toxicological Research Vol. No.
The present study was conducted to monitor the level of triflumizole residues in fruits (apple and pear) and vegetable (cucumber) samples in order to assess risk posed by the presence of such residues to the consumer. Triflumizole was applied at a recommended dose rate to apple and pear pulps and to a cucumber sample. The samples were collected at harvesting time following several treatments (three and/or four treatments). Triflumizole was extracted with methanol and re-extracted into dichloromethane. The presence of triflumizole was determined by HPLC with UV detection at 238 nm following the cleanup of the extract by open preparative chromatographic column with Florisil. The versatility of this method was evidenced by its excellent linearity (> 0.999) in the concentration range between 0.2 and 4.0 mg/kg. The mean recoveries evaluated from the untreated samples spiked at two different fortification levels. 0.1 and 0.4 mg/kg, and ranged from 87.5${\pm}$0.0 to 93.3${\pm}$2.6 for the tested fruits and vegetable, respectively, and the repeatability (as relative standard deviation) from three repetitive determinations of recoveries were no larger than 6%. The calculated limit of detection was 0.02 mg/kg and the minimum detectable level of 4 ng for triflumizole was easily detected. When triflumizole was sprayed onto the apple trees three times at 50-40-30 and 40-30-21 days prior to harvesting and four times onto the pear trees at 40-30-21-14 days prior to harvesting, the mean residual amounts of 0.05 and 0.06 mg/kg for apples and pears, respectively, were not detected in all of the treatments. When the cucumber sample was fumigated four times at 7, 5, 3 and 1 day prior to harvesting, the mean residual amount was not detectable. Triflumizole can be used safely when sprayed (wettable powder, 30% active ingredient) and fumigated (10%) 4 times at 14 and 1 day prior to harvesting to protect the fruits and vegetable, respectively.
Sathya Khay,Abd El-Aty Mostafa Abd El-Aty,Jeong-Heui Choi,Myeong-Seok Kim,Jin kyoung Kim,Jae-Han Shim 한국원예학회 2006 Horticulture, Environment, and Biotechnology Vol.47 No.5
The present investigation was undertaken to generate information about the residue levels and degradation rate of metalaxyl from Chinese cabbages (Brassica campestris) grown under greenhouse conditions. Metalaxyl of 25% wettable powder was applied with dilution of recommended and double doses to the crop. The Chinese cabbage shoots were harvested immediately after this application and at regular intervals over a 10-day. After harvesting, the metalaxyl residue was analyzed using gas chromatography equipped with a nitrogen-phosphorus detector. Initially deposited amount of the chemical in/on the crop right after application with recommended and double doses were 7.1 and 14.7 ㎎ㆍ㎏?¹ respectively. Ten days later, the residue had declined substantially to 0.1 and 0.5 ㎎ㆍ㎏?¹, respectively. These concentrations were below or approach the maximum residual limit (MRL = 0.5 ㎎ㆍ㎏?¹ for Chinese cabbage) established by the World Health Organization (WHO), respectively. The estimated dissipation half-life on the Chinese cabbages was 2.1 and 2.3 days, respectively. Thus, a 10-day interval following the spraying of metalaxyl on Chinese cabbages grown under greenhouse conditions was adequate to reduce the residue to levels below the MRL set by the WHO.