Sathya Khay

Simultaneous determination of pyrethroids from pesticide residues in porcine muscle and pasteurized milk using GC.

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.

Simultaneous determination of three acidic herbicide residues in food crops using HPLC and confirmation via LC-MS/MS.

2,4-D, dicamba and 4-CPA with auxin-like activity have been intensively used in agriculture, for the control of unwanted broadleaf weeds. An analytical method involving HPLC coupled with UVD was developed for the simultaneous analysis of these three analytes in Chinese cabbage, apple and pepper fruits (representative non-fatty samples) and brown rice and soybean (representative fatty samples) using liquid-liquid partitioning and column cleanup procedures. The residues were confirmed via tandem mass spectrometry (MS/MS) in ion electrospray ionization (ESI) mode. The standard curves were linear over the range of the tested concentrations (0.25-10 microg/mL), as shown by a marked linearity in excess of 0.9999 (r(2) ). The average recoveries (mean, n = 3) ranged from 94.30 to 102.63 in Chinese cabbage, from 94.76 to 108.47 in apple, from 97.52 to 102.27 in pepper, from 76.19 to 101.90 in brown rice, and from 74.60 to 107.39 in soybean. The relative standard deviations (RSDs) were <9% in all tested matrices. The limits of detection and quantitation were 0.006 and 0.02 mg/kg, respectively. Samples purchased from local markets were analyzed to evaluate the applicability of the methods developed herein. The concentration of the 2,4-D residue was measured at 0.102 mg/kg in the soybean sample; however, this level is exactly the same MRL set by the Korea Food and Drug Administration. This developed method deserves full and complete consideration, as it clearly displays the sensitivity, accuracy and precision required for residue analysis of 2,4-D, dicamba and 4-CPA in food crops.

Determination of Trichlorfon Pesticide Residues in Milk via Gas Chromatography with μ-Electron Capture Detection and GC-MS.

The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with μ-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and 11.1 μg/l, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to 250 μg/l. The intra- and inter-day accuracy (n = 6) ranged from 89.2%to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples.

Approaches for application of sub and supercritical fluid extraction for quantification of orbifloxacin from plasma and milk: Application to disposition kinetics

Since its extensive development in the early 1980s, SFE has attracted considerable attention as a sample-preparation procedure. However, other different sample preparation procedures, including precipitation, liquid- and/or solid-phase extraction in biological fluids, also remain in use. In this investigation, SFE was introduced to isolate and identify orbifloxacin from plasma and milk. Four parameters, including the temperature and the pressure of supercritical fluid, modifier ratios, and dynamic extraction time, were evaluated and optimized to obtain the best yield of the analyte from the biological fluids. Determinations of the orbifloxacin (OBFX) in the extracts were carried out using HPLC-FLD. The optimum conditions of the extraction process that yielded the maximum analyte extraction efficiencies were 150 degrees C vs. 60 degrees C, 250 kg cm(-2), 30% vs. 35% methanol, and 40 min vs. 20 min, for plasma and milk, respectively. The linearity of the calibration curves as well as the instrument LODs/LOQs were evaluated. Good linearity (at least r(2) > or = 0.999) of the calibration curves was obtained over the range from 0.2 to 0.01 microg mL(-1). The method showed a good recovery rate (74.2-127.73%) and precision (RSDs: 1.64-20%). The instrumental LOD and LOQ values were 0.004 microg mL(-1) vs. 0.01 microg mL(-1) or 0.006 microg mL(-1) vs. 0.02 microg mL(-1), for plasma and milk, respectively. The method was successfully applied to estimate the pharmacokinetic variables of orbifloxacin in lactating does. To the best of our knowledge, this is the first time that SFE has been applied to isolate an antimicrobial agent from biological fluids. This method is promising for clinical applications and for pharmacokinetic studies of various pharmaceuticals in biological fluids.

Analytical procedure to simultaneously measure trace amounts of trenbolone acetate and β‐trenbolone residues in porcine muscle using HPLC‐UVD and MS

The current study was undertaken to validate the performance for the determination of both TBA and beta-trenbolone (beta-TB) residues in porcine muscle at concentrations required to monitor compliance with the maximum residue limit (MRL). The method involves a one phase liquid-liquid extraction, cleanup with low-temperature fat precipitation, separation of the respective compounds by HPLC on a Capcell pak C(18) column, use of a methanol-water isocratic system as an eluent, and measurement by UV absorbance detection at 340 nm. Both compounds were confirmed using LC-MS/MS with electrospray interface (ESI) and a triple quadrupole (QqQ) analyzer. The method was found to be precise and accurate, with a linearity range of 1-10 microg/kg (r(2) >0.973). The intra- and interday precision showed good reproducibility with RSDs < or =13.25%. The LODs were 0.12 and 0.22 microg/kg, and the LOQs were 0.37 and 0.66 microg/kg, for TBA and beta-TB, 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 compounds were detected in any of the samples. The advantages of our method are that it is: selective, sensitive, requires a short time for analysis (13 min), and performs simple sample extraction and clean-up procedure with low-temperature fat precipitation as compared to the previously published methods.

Development of extraction procedures for the determination of imidacloprid: application to residue analysis and dynamics of two formulations in Chinese cabbage.

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.

Analysis of Residual Triflumizole, an Imidazole Fungicide, in Apples, Pears and Cucumbers Using High Performance Liquid Chromatography

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 ± 0.0 to 93.3 ± 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.

Residues of Diazinon in Growing Chinese cabbage: A study Under Greenhouse Conditions

Chinese cabbage, Braccica campestris has long been consumed as a staple food for Koreans in various forms of fresh, salted, and fermented Kimchi. Cultivation of the crop under greenhouse has become a general practices to fulfill its off-seasonal consumers demand. However, agricultural practices of the crop have always accompanied with heavy applications of pesticides caused by severe outbreaks of diseases and pose under warm and humid circumferences. Since dissipation patterns of pesticide residues in/on the crop under greenhouse conditions ate quite different from those in the open-air, changes of diazinon, O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphornthioate, in/on the Chinese cabbage applied by foliar spraying under greenhouse were studied. Diazinon 34% EC was applied with dilution of recommended and double dose to the crop. The shoots of crop were harvested immediately after this application and at regular intervals over a 10-day. After sample preparations, the diazinon residue was analyzed using gas chromatography equipped with electron capture detector (GC/ECD). Initially deposited amount of the chemical in/on the crop right after applications with recommended and double doses were 8.3 and 15.2 mg/kg, respectively. The residue levels after 10 days of application were 0.03 and 0.09 mg/kg with 1.3 and 1.5 days of half-life in/on the crop, respectively. In consequent 10 days of pre-harvest interval (PHI) for diazinon EC formulation in/on Chinese cabbage under greenhouse condition was fulfill maximum residue level set by Korea Food and Drug Administration (KFDA, 0.1 mg/kg).