Analysis of 10 systemic pesticide residues in various baby foods using liquid chromatography-tandem mass spectrometry.

Ten systemic pesticides, comprising methomyl, thiamethoxam, acetamiprid, carbofuran, fosthiazate, metalaxyl, azoxystrobin, diethofencarb, propiconazole, and difenoconazole, were detected in 13 baby foods (cereals, boiled potatoes, fruit and milk) using QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) for sample preparation and liquid chromatography tandem mass spectrometry for analysis. The matrix-matched calibration curves showed good linearity with determination coefficients (R(2) ) >0.992. The limits of detection and quantitation were 0.0015-0.003 and 0.005-0.01 mg/kg, respectively. The mean recoveries of three different concentrations ranged from 69.2 to 127.1% with relative standard deviations <20%. The method was successfully applied to 13 actual samples collected from a local market, and none of the samples were found to contain pesticide residues. This method is suitable for the identification and quantification of systemic pesticides with matrix-matched standards in various baby foods.

Analysis of etoxazole in red pepper after major modification of QuEChERS for gas chromatography-nitrogen phosphorus detection.

A major modification to the QuEChERS (quick, easy, cheap, effective, rugged and safe) method was developed for the analysis of etoxazole in red pepper using gas chromatography coupled with a nitrogen-phosphorus detector. Etoxazole was extracted with acetonitrile, partitioned with magnesium sulfate and purified with a solid-phase extraction cartridge. The method showed good linearity with a determination coefficient (R(2) ) of 0.998 for the 0.02-2.0 mg/L concentration range. The method was validated using blank red pepper spiked at 0.2 and 1.0 mg/kg, and the average recovery rate was 74.4-79.1% with relative standard deviations <5% for intra- and inter-day precision. The limits of detection and quantification were 0.007 and 0.02 mg/kg, respectively. The developed method was successfully applied to field-incurred samples, and the presence of etoxazole residues was confirmed using gas chromatography/mass spectrometry.

Determination of kresoxim-methyl and its thermolabile metabolites in pear utilizing pepper leaf matrix as a protectant using gas chromatography.

Kresoxim-methyl and its two thermolabile metabolites, BF 490-2 and BF 490-9, were analyzed in pear using a pepper leaf matrix protection to maintain the metabolites inside the gas chromatography system. Samples were extracted with a mixture of ethyl acetate and n-hexane (1:1, v/v) and purified and/or separated using a solid phase extraction procedure. The pepper leaf matrix was added and optimized with cleaned pear extract to enhance metabolite sensitivity. Matrix matched calibration was used for kresoxim-methyl in the pear matrix and for metabolites in the pear mixed with pepper leaf matrix. Good linearity was obtained for all analytes with a coefficient of determination, r (2) â©¾ 0.992. Limits of detection (LOD) and quantification (LOQ) were 0.006 and 0.02 mg kg(-1) and 0.02 and 0.065 mg kg(-1) for kresoxim-methyl and the metabolites, respectively. Recoveries were carried out at two concentration levels and were 85.6-97.9% with a relative standard deviation <2.5%. The method was successfully applied to field incurred pear samples, and only kresoxim-methyl was detected at a concentration of 0.03 mg kg(-1).

Dissipation pattern and pre-harvest residue limit of abamectin in perilla leaves.

The pre-harvest residue limit (PHRL) of abamectin (abamectin B1a and B1b) in Perilla frutescens leaves grown under greenhouse conditions were investigated using high-performance liquid chromatography with a fluorescence detector. Samples were extracted with acetonitrile. The extract was purified through a solid phase extraction procedure. Then the purified extract was derivatized with trifluoroacetic anhydride and N-methylimidazole to form a strong stable fluorescent derivative of abamectin. Finally, derivatized abamectins were conveyed to the detector via an Atlantis C18 column, with water and methanol as a mobile phase. Calibration curves were linear over the calibration ranges with coefficients of determinants r (2) ≥ 0.999. The limits of detection and quantification were 0.0033 and 0.01 mg kg(-1) for abamectin B1a and B1b, respectively. Recovery was assessed in a control matrix at two different fortification concentrations, with three replicates for each concentration. Good recoveries were obtained for the target analytes and ranged from 82.11 to 93.03%, with relative standard deviations of less than 8%. The rate of disappearance of total abamectin on perilla leaves for recommended and double the recommended doses was described as first-order kinetics with a half-life of 0.7 days. Using the PHRL curve, we could predict the residue level of total abamectin to be 0.92 mg kg(-1) at 7 days before harvest or 0.26 mg kg(-1) at 4 days before harvest, which would be below the provisional MRL designed by the Korea Food and Drug Administration.

A QuEChERS-based extraction method for the residual analysis of pyraclofos and tebufenpyrad in perilla leaves using gas chromatography: application to dissipation pattern.

The objective of this work was to establish a simple extraction method for the residual analysis of pyraclofos and tebufenpyrad in Perilla leaves. A QuEChERS (quick, easy, cheap, effective, rugged and safe) method was used for extraction using ethyl acetate as an extraction solvent, and cleanup was carried out using dispersive solid-phase extraction technique. The samples were analyzed using gas chromatography with nitrogen phosphorous detector and confirmed by gas chromatography-mass spectrometry. The linearity was excellent (r(2) = 1.0) in matrix-matched calibration for both pesticides. The recoveries at two fortification levels were 80.76-95.38% with relative standard deviation lower than 5%. The limits of detection and limits of quantification were 0.01 and 0.033 mg/kg for both pesticides, respectively. The results revealed that the dissipation pattern of pyraclofos and tebufenpyrad followed first-order kinetics. The pyraclofos and tebufenpyrad residues declined to a level below the maximum residue limits within 14 day between the last application and harvesting. We suggest that pyraclofos and tebufenpyrad could be used efficiently on perilla leaves under the recommended dosage conditions.

Feasibility and application of an HPLC/UVD to determine dinotefuran and its shorter wavelength metabolites residues in melon with tandem mass confirmation.

A new analytical method was developed for dinotefuran and its metabolites, MNG, UF, and DN, in melon using high-performance liquid chromatography (HPLC) coupled with an ultraviolet detector (UVD). Due to shorter wavelength, lower sensitivity to UV detection, and high water miscibility of some metabolites, QuEChERs acetate-buffered version was modified for extraction and purification. Mobile phases with different ion pairing or ionisation agents were tested in different reverse phase columns, and ammonium bicarbonate buffer was found as the best choice to increase the sensitivity of target analytes to the UV detector. After failure of dispersive SPE clean-up with primary secondary amine, different solid phase extraction cartridges (SPE) were used to check the protecting capability of analytes against matrix interference. Finally, samples were extracted with a simple and rapid method using acetonitrile and salts, and purified through C(18)SPE. The method was validated at two spiking levels (three replicates for each) in the matrix. Good recoveries were observed for all of the analytes and ranged between 70.6% and 93.5%, with relative standard deviations of less than 10%. Calibration curves were linear over the calibration ranges for all the analytes with r(2)≥ 0.998. Limits of detection ranged from 0.02 to 0.05 mg kg(-1), whereas limits of quantitation ranged from 0.06 to 0.16 mg kg(-1) for dinotefuran and its metabolites. The method was successfully applied to real samples, where dinotefuran and UF residues were found in the field-incurred melon samples. Residues were confirmed via LC-tandem mass spectrometry (LC-MS/MS) in positive-ion electrospray ionisation (ESI(+)) mode.

Analysis of kresoxim-methyl and its thermolabile metabolites in Korean plum: An application of pepper leaf matrix as a protectant for GC amenable metabolites.

A new method was developed for kresoxim-methyl (parent compound) and its two thermolabile metabolites, BF 490-2 and BF 490-9, in Korean plum, introducing pepper leaf matrix as a natural analyte protectant for GC-amenable metabolites using a GC-electron capture detector. Samples were extracted with a simple and rapid method using a mixture of ethyl acetate-n-hexane (1:1) and salts, and purified via SPE. Due to the elution gap between parent compound and metabolites in the SPE cartridge and matrix interference, kresoxim-methyl was isolated separately from its metabolites. An optimized amount of pepper leaf matrix (0.25 g/mL) was added to the metabolites prior to each injection. Calibration curves were linear over the concentration ranges with coefficient of determination (r(2)) ≥ 0.999. The method was validated in triplicate at two fortification levels, giving recoveries ranging between 74.3 and 101.4%, and RSDs less than 5%. The LOD and LOQ were 0.015 and 0.05 mg/kg, respectively. The method was successfully applied to real samples where kresoxim-methyl residues were detected in field-incurred plum samples. Residues were confirmed using GC-MS.

Development of an extraction method for the determination of avermectins in soil using supercritical CO2 modified with ethanol and liquid chromatography-tandem mass spectrometry.

The aim of the present study was to develop a multiresidue analytical method for determination of avermectins (abamectin, ivermectin, moxidectin, and doramectin) in soil samples using supercritical fluid extraction and LC-MS/MS. The optimal extraction conditions for supercritical fluid extraction were 80°C for temperature, 300 kg/cm(2) for pressure, 40 min as an extraction time, and 30% of a modifier ratio. The linearity of the calibration curves was excellent and yielded the correlation coefficients (r(2) = 0.998-0.999, at a range of 1.5-500 ng/g). Soil samples were fortified with known quantities of the analytes at three different concentration levels (5, 10, and 50 ng/g) and the recoveries were in the range of 82.5-96.2% with relative standard deviation values ranging between 2.1 and 7.9%. The limits of detections and limits of quantitations were 1.5 and 5 ng/g, respectively. The developed method was successfully applied to analyze avermectin residues in soil samples collected from 13 sites in the Honam area, Republic of Korea. In sum, a combination of supercritical fluid extraction and LC-MS/MS has been proven to be highly efficient as an environmentally friendly technique for the simultaneous determination of avermectins in soil samples.

Single-step modified QuEChERS for determination of chlorothalonil in shallot (Allium ascalonicum) using GC-µECD and confirmation via mass spectrometry.

A single extraction method was developed for chlorothalonil in shallot using gas chromatography with an electron capture detector (GC-µECD). Samples were extracted with single-step modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method using ethyl acetate as an extraction solvent. Significant matrix effects were observed, and the calibration curve was constructed from the matrix. The linearity of the analytical response across the studied range of concentrations (0.01-1.00 mg/L) was excellent, obtaining a correlation coefficient (r(2) ) of 0.996. >0.996. Recovery studies were carried out on spiked shallot blank samples, at two concentration levels (0.4 and 2.0 mg/kg) with three replicates performed at each level. Mean recoveries of 97.2-104.9% with RSDs of 1.3-2.7% were obtained. The method is demonstrated to be suitable for the determination of chlorothalonil in shallot. The dissipation rates of chlorothalonil were described using first-order kinetics, and its half-life was 2.8 days. Based on the dissipation pattern of the pesticide residues, the pre-harvest residue limit (PHRL) was also calculated. Residues were confirmed via mass spectrometry.

Characterization of secondary volatile profiles in Nigella sativa seeds from two different origins using accelerated solvent extraction and gas chromatography-mass spectrometry.

The extraction and identification of bioactive compounds from herbs is of great interest. In this study, accelerated solvent extraction (ASE) technique was used to analyze the secondary volatile profiles in Nigella sativa seeds obtained from two different origins, Egypt and Bangladesh. The main extraction parameters, including extraction temperature, pressure and static extraction time, were investigated and optimized. Identification and quantification of the major constituents in nonpolar extracts (hexane) were achieved by means of GC-FID/GC-MS analysis with external standards. The two seeds showed a similar variety of chemical composition; however, the secondary volatiles profile of Bangladesh seed was higher than that of the Egyptian seed. A total of 25 compounds were identified from the ASE extract under the following optimum extraction conditions: 100°C, 1500 psi and 5 min, for extraction temperature, pressure and static time, respectively. The proposed technique can be used for the characterization of N. sativa varieties or cultivars.

Determination of spinetoram and its metabolites in amaranth and parsley using QuEChERS-based extraction and liquid chromatography-tandem mass spectrometry.

In this study, a simultaneous method was developed for the determination of spinetoram (XDE-175-J and XDE-175-L) and its demethyl metabolites (N-demethyl-175-J and N-demethyl-175-L) and formyl metabolites (N-formyl-175-J and N-formyl-175-L) in the minor crops; amaranth and parsley. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction. Afterwards, the analytes were quantified and confirmed via liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM). Calibration curves were linear over the calibration ranges for all the analytes tested with r(2)>0.993. Limits of detection and quantitation were 0.01 and 0.03 mg/kg for all the tested analytes in amaranth and parsley, respectively. Recovery values, at spiking levels 0.05 and 0.25 mg/kg, ranged from 71.0% to 115.2% with relative standard deviations <15%, except for N-formyl-175-J in both amaranth and parsley. This method was applied to field-incurred samples and was shown to provide an adequate sensitivity and performance for the simultaneous determination of spinetoram and metabolites. To the best of our knowledge, this is the first time spinetoram and its metabolites were quantified using LC-MS/MS in minor crops.