A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-am... more A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-aminobenzoic acid as the coupling agent was developed. The determination involves on-line hydrolysis at room temperature of the propoxur with sodium hydroxide. The resulting 2-isopropoxyphenol is coupled with diazotized 4-aminobenzoic acid in order to achieve an appropriate selectivity and sensitivity to the spectrophotometric measurements. The calibration curve is
ABSTRACT A procedure has been developed for the determination of quinclorac, bentazone, 2,4-D, cl... more ABSTRACT A procedure has been developed for the determination of quinclorac, bentazone, 2,4-D, clomazone, and propanil residues in surface and agriculture waters by SPE and HPLC-UV. The method was validated and was applied for levels between 0.1 and 0.5 g/L, after a 500-fold pre-concentration. Average recoveries ranged from 85.7 to 109.8% with overall relative standard deviations of 1.8 to 13.4%.
The development of green, economical and sustainable chemical processes is one of the primary cha... more The development of green, economical and sustainable chemical processes is one of the primary challenges in organic synthesis. Herein, we report an efficient and heterogeneous palladium-catalyzed sulfonylation of vinyl cyclic carbonates with sodium sulfinates via decarboxylative cross-coupling. Both aliphatic and aromatic sulfinate salts react with various vinyl cyclic carbonates to deliver the desired allylic sulfones featuring tri-and even tetrasubstituted olefin scaffolds in high yields with excellent selectivity. The process needs only 2 mol% of Pd 2 (dba) 3 and the in situ formed palladium nano-particles are found to be the active catalyst. Scheme 1 Cross coupling of vinyl cyclic carbonates for C-S bond formation. (a) Homogeneous catalysis (b) heterogeneous catalysis.
Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment, 2017
A method for the determination of five sedatives and 14 β-blocker residues in swine, bovine and e... more A method for the determination of five sedatives and 14 β-blocker residues in swine, bovine and equine kidney was validated. Samples were extracted with acetonitrile and purified using dispersive solid phase extraction (d-SPE) with Celite 545 with subsequent analysis by LC-MS/MS. A simplified protocol was applied to validate the method scope extension to include new matrices. Parameters such as recovery, trueness, linearity (r(2)), relative standard deviation (RSD), decision limit (CCα) and method capability (CCβ) were measured for the bovine and equine kidney matrices. The method was applied to the analysis of more than 300 real samples and is currently included in the Brazilian National Residue Control Plan.
Page 1. Quim. Nova, Vol. 33, No. 6, 1335-1341, 2010 Artigo *e-mail: dqmdoca@furg. br S??NTESE DE ... more Page 1. Quim. Nova, Vol. 33, No. 6, 1335-1341, 2010 Artigo *e-mail: dqmdoca@furg. br S??NTESE DE NOVAS AMIDAS GRAXAS A PARTIR DA AMIN??LISE DE ??STERES MET??LICOS Carolina R. Lopes, Caroline Da Ros Montes ...
A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in... more A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in tomatoes and cucumbers grown in experimental greenhouses was developed and validated. The vegetables were submitted to a single spraying with chlorothalonil at half, equal to and double of the recommended dose. Chlorothalonil residues were extracted in Ultra-Turrax system using ethyl acetate in the presence of anhydrous sodium sulphate and determined by gas chromatography with electron capture detection. The analytical curves were linear from 0.005 to 5.0 mg L-1, with coefficient of determination higher then 0.995. The assays provide acceptable results with RSD values below 10.5% and recoveries were between 92.2 and 114.5% for tomatoes, and between 86.2 and 103.3% for cucumbers, both obtained from spiked samples at 0.028, 0.28, 2.8 and 5.0 mg kg-1 levels. Statistical interpretation of residue levels fitted to a first-order model for the dissipation behavior of chlorothalonil. The mean h...
The presence of the pyrethroids residues in different samples and the impact on human health is a... more The presence of the pyrethroids residues in different samples and the impact on human health is an increasing concern due to their widespread use. So, a method to determine eighteen pyrethroids in fish samples using a modified QuEChERS was developed. The clean-up procedure was performed by freezing samples overnight followed by dispersive solid phase extraction. The combination of C18, PSA and Z-Sep+ was optimized using a mixture design approach and samples were analysed using gas chromatography mass spectrometry. The method was validated using trahira samples and a scope extension was performed for tilapia and tainha. Recoveries were within 63-129%, relative standard deviation was ≤21.5% and the quantification limits were 5 µg kg-1 or 10 µg kg-1. The applicability of the method was assessed by analysis of fourteen real samples, in which residues were detected in four samples. Such detections demonstrate the importance of this sensitive method.
A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea... more A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea, organophosphate, pyrimidinamine, pyrethrin and pyrethroid classes in salmon by liquid chromatography coupled with tandem mass spectrometry. Samples were extracted with acetonitrile-water as the extraction solvent with use of a vibrational shaking apparatus with a ceramic homogenizer. After extraction, the acetonitrile extracts were cleaned up by incubation at low temperature (-20°C, 1 h) to remove fat, followed by dispersive solid-phase extraction using Z-Sep+ and primary-secondary amine as sorbents. Validation was performed following the 2002/657/EC and SANTE/11813/2017 guidelines. The trueness of the method ranged from 87% to 121% and precision ranged from 4.1% to 23.7%, with the exception of cyphenothrin, dicyclanil and azamethiphos. The method developed is particularly advantageous because the use of a vibrational shaker allows unattended extraction of samples and eliminates a laborious tissue disruption step, which increases sample throughput in the laboratory. The sample preparation and chromatographic separations can be performed in 5 and 4 h, respectively, for 36 samples.
In this work, a method was developed, validated, and applied to determination of ten pesticide re... more In this work, a method was developed, validated, and applied to determination of ten pesticide residues (trifluralin, carbofuran, chlorothalonil, pendimethalin, captan, tebuconazole, pyraclostrobin, difenoconazole, deltamethrin, and azoxystrobin), from seven distinct classes, in carrot samples, employing a QuEChERS procedure for the analyte extraction and gas chromatography coupled to mass spectrometry (GC-MS) for quantification. The dispersive clean-up step was optimized using different sorbents at different concentrations and mixings. The method proved to be efficient and robust, showing recoveries in the range 72-117%, and RSD ranging from 4.9 to 16.6% (except for chlorothalonil and captan) at fortification levels of 45, 90, 180, and 450 μg kg -1 with seven replicates analyzed for each level (n = 28). Chlorothalonil and captan could not be validated due to analyte stability problems. Detection limits were between 15 and 45 μg kg -1 , and the quantification limits were between 45 and 90 μg kg -1 . The method was successfully applied to real samples.
Recebido em 25/9/06; aceito em 4/5/07; publicado na web em 25/10/07 In this work the exposure of ... more Recebido em 25/9/06; aceito em 4/5/07; publicado na web em 25/10/07 In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cropping, was assessed. Water consumption wells and surface water flows were sampled at different times. After a preconcentration step with solid phase extraction (SPE), the selected pesticides were determined by gas chromatography with electron capture detection (GC-ECD) or high performance liquid chromatography with diode array detection (HPLC-DAD). No pesticides were detected in the well water samples and surface water flow in the winter season. However, in the spring and summer higher concentrations of chlorpyrifos and imidacloprid were found in the water source samples. Atrazine, simazine and clomazone were also found. The occurrence of pesticides in collected water samples was related with the application to tobacco.
A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in... more A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in tomatoes and cucumbers grown in experimental greenhouses was developed and validated. The vegetables were submitted to a single spraying with chlorothalonil at half, equal to and double of the recommended dose. Chlorothalonil residues were extracted in Ultra-Turrax system using ethyl acetate in the presence of anhydrous sodium sulphate and determined by gas chromatography with electron capture detection. The analytical curves were linear from 0.005 to 5.0 mg L-1, with coefficient of determination higher then 0.995. The assays provide acceptable results with RSD values below 10.5% and recoveries were between 92.2 and 114.5% for tomatoes, and between 86.2 and 103.3% for cucumbers, both obtained from spiked samples at 0.028, 0.28, 2.8 and 5.0 mg kg-1 levels. Statistical interpretation of residue levels fitted to a first-order model for the dissipation behavior of chlorothalonil. The mean h...
The presence of the pyrethroids residues in different samples and the impact on human health is a... more The presence of the pyrethroids residues in different samples and the impact on human health is an increasing concern due to their widespread use. So, a method to determine eighteen pyrethroids in fish samples using a modified QuEChERS was developed. The clean-up procedure was performed by freezing samples overnight followed by dispersive solid phase extraction. The combination of C18, PSA and Z-Sep+ was optimized using a mixture design approach and samples were analysed using gas chromatography mass spectrometry. The method was validated using trahira samples and a scope extension was performed for tilapia and tainha. Recoveries were within 63-129%, relative standard deviation was ≤21.5% and the quantification limits were 5 µg kg-1 or 10 µg kg-1. The applicability of the method was assessed by analysis of fourteen real samples, in which residues were detected in four samples. Such detections demonstrate the importance of this sensitive method.
DEVELOPMENT OF EXTRACTION PROCEDURE FOR ANALYSIS OF SEDATIVES AND β-BLOCKERS IN SWINE KIDNEY. A p... more DEVELOPMENT OF EXTRACTION PROCEDURE FOR ANALYSIS OF SEDATIVES AND β-BLOCKERS IN SWINE KIDNEY. A procedure was developed for determination of 5 sedatives and 14 β-blockers in swine kidney and subsequent analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Three different procedures for extraction were tested, evaluated through recovery studies. The procedure using acetonitrile for extraction and cleanup with freezing at low temperature and dispersive solid phase extraction using 500 mg celite ® 545 before the concentration step presented the better results. The dried samples were redissolved with methanol and analyzed using a LC-MS/MS system with electrospray ionization (ESI) operating in positive MRM mode. The recovery values for this procedure were in the 75-88% range. The robustness of the method was tested against small variations. The method was used to analyze carazolol, azaperone and azaperol in collaborative assay, obtaining results close to designed value.
A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea... more A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea, organophosphate, pyrimidinamine, pyrethrin and pyrethroid classes in salmon by liquid chromatography coupled with tandem mass spectrometry. Samples were extracted with acetonitrile-water as the extraction solvent with use of a vibrational shaking apparatus with a ceramic homogenizer. After extraction, the acetonitrile extracts were cleaned up by incubation at low temperature (-20°C, 1 h) to remove fat, followed by dispersive solid-phase extraction using Z-Sep+ and primary-secondary amine as sorbents. Validation was performed following the 2002/657/EC and SANTE/11813/2017 guidelines. The trueness of the method ranged from 87% to 121% and precision ranged from 4.1% to 23.7%, with the exception of cyphenothrin, dicyclanil and azamethiphos. The method developed is particularly advantageous because the use of a vibrational shaker allows unattended extraction of samples and eliminates a laborious tissue disruption step, which increases sample throughput in the laboratory. The sample preparation and chromatographic separations can be performed in 5 and 4 h, respectively, for 36 samples.
In this work, a method was developed, validated, and applied to determination of ten pesticide re... more In this work, a method was developed, validated, and applied to determination of ten pesticide residues (trifluralin, carbofuran, chlorothalonil, pendimethalin, captan, tebuconazole, pyraclostrobin, difenoconazole, deltamethrin, and azoxystrobin), from seven distinct classes, in carrot samples, employing a QuEChERS procedure for the analyte extraction and gas chromatography coupled to mass spectrometry (GC-MS) for quantification. The dispersive clean-up step was optimized using different sorbents at different concentrations and mixings. The method proved to be efficient and robust, showing recoveries in the range 72-117%, and RSD ranging from 4.9 to 16.6% (except for chlorothalonil and captan) at fortification levels of 45, 90, 180, and 450 μg kg −1 with seven replicates analyzed for each level (n = 28). Chlorothalonil and captan could not be validated due to analyte stability problems. Detection limits were between 15 and 45 μg kg −1 , and the quantification limits were between 45 and 90 μg kg −1. The method was successfully applied to real samples.
In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cro... more In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cropping, was assessed. Water consumption wells and surface water flows were sampled at different times. After a preconcentration step with solid phase extraction (SPE), the selected pesticides were determined by gas chromatography with electron capture detection (GC-ECD) or high performance liquid chromatography with diode array detection (HPLC-DAD). No pesticides were detected in the well water samples and surface water flow in the winter season. However, in the spring and summer higher concentrations of chlorpyrifos and imidacloprid were found in the water source samples. Atrazine, simazine and clomazone were also found. The occurrence of pesticides in collected water samples was related with the application to tobacco.
A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-am... more A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-aminobenzoic acid as the coupling agent was developed. The determination involves on-line hydrolysis at room temperature of the propoxur with sodium hydroxide. The resulting 2-isopropoxyphenol is coupled with diazotized 4-aminobenzoic acid in order to achieve an appropriate selectivity and sensitivity to the spectrophotometric measurements. The calibration curve is
ABSTRACT A procedure has been developed for the determination of quinclorac, bentazone, 2,4-D, cl... more ABSTRACT A procedure has been developed for the determination of quinclorac, bentazone, 2,4-D, clomazone, and propanil residues in surface and agriculture waters by SPE and HPLC-UV. The method was validated and was applied for levels between 0.1 and 0.5 g/L, after a 500-fold pre-concentration. Average recoveries ranged from 85.7 to 109.8% with overall relative standard deviations of 1.8 to 13.4%.
The development of green, economical and sustainable chemical processes is one of the primary cha... more The development of green, economical and sustainable chemical processes is one of the primary challenges in organic synthesis. Herein, we report an efficient and heterogeneous palladium-catalyzed sulfonylation of vinyl cyclic carbonates with sodium sulfinates via decarboxylative cross-coupling. Both aliphatic and aromatic sulfinate salts react with various vinyl cyclic carbonates to deliver the desired allylic sulfones featuring tri-and even tetrasubstituted olefin scaffolds in high yields with excellent selectivity. The process needs only 2 mol% of Pd 2 (dba) 3 and the in situ formed palladium nano-particles are found to be the active catalyst. Scheme 1 Cross coupling of vinyl cyclic carbonates for C-S bond formation. (a) Homogeneous catalysis (b) heterogeneous catalysis.
Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment, 2017
A method for the determination of five sedatives and 14 β-blocker residues in swine, bovine and e... more A method for the determination of five sedatives and 14 β-blocker residues in swine, bovine and equine kidney was validated. Samples were extracted with acetonitrile and purified using dispersive solid phase extraction (d-SPE) with Celite 545 with subsequent analysis by LC-MS/MS. A simplified protocol was applied to validate the method scope extension to include new matrices. Parameters such as recovery, trueness, linearity (r(2)), relative standard deviation (RSD), decision limit (CCα) and method capability (CCβ) were measured for the bovine and equine kidney matrices. The method was applied to the analysis of more than 300 real samples and is currently included in the Brazilian National Residue Control Plan.
Page 1. Quim. Nova, Vol. 33, No. 6, 1335-1341, 2010 Artigo *e-mail: dqmdoca@furg. br S??NTESE DE ... more Page 1. Quim. Nova, Vol. 33, No. 6, 1335-1341, 2010 Artigo *e-mail: dqmdoca@furg. br S??NTESE DE NOVAS AMIDAS GRAXAS A PARTIR DA AMIN??LISE DE ??STERES MET??LICOS Carolina R. Lopes, Caroline Da Ros Montes ...
A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in... more A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in tomatoes and cucumbers grown in experimental greenhouses was developed and validated. The vegetables were submitted to a single spraying with chlorothalonil at half, equal to and double of the recommended dose. Chlorothalonil residues were extracted in Ultra-Turrax system using ethyl acetate in the presence of anhydrous sodium sulphate and determined by gas chromatography with electron capture detection. The analytical curves were linear from 0.005 to 5.0 mg L-1, with coefficient of determination higher then 0.995. The assays provide acceptable results with RSD values below 10.5% and recoveries were between 92.2 and 114.5% for tomatoes, and between 86.2 and 103.3% for cucumbers, both obtained from spiked samples at 0.028, 0.28, 2.8 and 5.0 mg kg-1 levels. Statistical interpretation of residue levels fitted to a first-order model for the dissipation behavior of chlorothalonil. The mean h...
The presence of the pyrethroids residues in different samples and the impact on human health is a... more The presence of the pyrethroids residues in different samples and the impact on human health is an increasing concern due to their widespread use. So, a method to determine eighteen pyrethroids in fish samples using a modified QuEChERS was developed. The clean-up procedure was performed by freezing samples overnight followed by dispersive solid phase extraction. The combination of C18, PSA and Z-Sep+ was optimized using a mixture design approach and samples were analysed using gas chromatography mass spectrometry. The method was validated using trahira samples and a scope extension was performed for tilapia and tainha. Recoveries were within 63-129%, relative standard deviation was ≤21.5% and the quantification limits were 5 µg kg-1 or 10 µg kg-1. The applicability of the method was assessed by analysis of fourteen real samples, in which residues were detected in four samples. Such detections demonstrate the importance of this sensitive method.
A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea... more A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea, organophosphate, pyrimidinamine, pyrethrin and pyrethroid classes in salmon by liquid chromatography coupled with tandem mass spectrometry. Samples were extracted with acetonitrile-water as the extraction solvent with use of a vibrational shaking apparatus with a ceramic homogenizer. After extraction, the acetonitrile extracts were cleaned up by incubation at low temperature (-20°C, 1 h) to remove fat, followed by dispersive solid-phase extraction using Z-Sep+ and primary-secondary amine as sorbents. Validation was performed following the 2002/657/EC and SANTE/11813/2017 guidelines. The trueness of the method ranged from 87% to 121% and precision ranged from 4.1% to 23.7%, with the exception of cyphenothrin, dicyclanil and azamethiphos. The method developed is particularly advantageous because the use of a vibrational shaker allows unattended extraction of samples and eliminates a laborious tissue disruption step, which increases sample throughput in the laboratory. The sample preparation and chromatographic separations can be performed in 5 and 4 h, respectively, for 36 samples.
In this work, a method was developed, validated, and applied to determination of ten pesticide re... more In this work, a method was developed, validated, and applied to determination of ten pesticide residues (trifluralin, carbofuran, chlorothalonil, pendimethalin, captan, tebuconazole, pyraclostrobin, difenoconazole, deltamethrin, and azoxystrobin), from seven distinct classes, in carrot samples, employing a QuEChERS procedure for the analyte extraction and gas chromatography coupled to mass spectrometry (GC-MS) for quantification. The dispersive clean-up step was optimized using different sorbents at different concentrations and mixings. The method proved to be efficient and robust, showing recoveries in the range 72-117%, and RSD ranging from 4.9 to 16.6% (except for chlorothalonil and captan) at fortification levels of 45, 90, 180, and 450 μg kg -1 with seven replicates analyzed for each level (n = 28). Chlorothalonil and captan could not be validated due to analyte stability problems. Detection limits were between 15 and 45 μg kg -1 , and the quantification limits were between 45 and 90 μg kg -1 . The method was successfully applied to real samples.
Recebido em 25/9/06; aceito em 4/5/07; publicado na web em 25/10/07 In this work the exposure of ... more Recebido em 25/9/06; aceito em 4/5/07; publicado na web em 25/10/07 In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cropping, was assessed. Water consumption wells and surface water flows were sampled at different times. After a preconcentration step with solid phase extraction (SPE), the selected pesticides were determined by gas chromatography with electron capture detection (GC-ECD) or high performance liquid chromatography with diode array detection (HPLC-DAD). No pesticides were detected in the well water samples and surface water flow in the winter season. However, in the spring and summer higher concentrations of chlorpyrifos and imidacloprid were found in the water source samples. Atrazine, simazine and clomazone were also found. The occurrence of pesticides in collected water samples was related with the application to tobacco.
A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in... more A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in tomatoes and cucumbers grown in experimental greenhouses was developed and validated. The vegetables were submitted to a single spraying with chlorothalonil at half, equal to and double of the recommended dose. Chlorothalonil residues were extracted in Ultra-Turrax system using ethyl acetate in the presence of anhydrous sodium sulphate and determined by gas chromatography with electron capture detection. The analytical curves were linear from 0.005 to 5.0 mg L-1, with coefficient of determination higher then 0.995. The assays provide acceptable results with RSD values below 10.5% and recoveries were between 92.2 and 114.5% for tomatoes, and between 86.2 and 103.3% for cucumbers, both obtained from spiked samples at 0.028, 0.28, 2.8 and 5.0 mg kg-1 levels. Statistical interpretation of residue levels fitted to a first-order model for the dissipation behavior of chlorothalonil. The mean h...
The presence of the pyrethroids residues in different samples and the impact on human health is a... more The presence of the pyrethroids residues in different samples and the impact on human health is an increasing concern due to their widespread use. So, a method to determine eighteen pyrethroids in fish samples using a modified QuEChERS was developed. The clean-up procedure was performed by freezing samples overnight followed by dispersive solid phase extraction. The combination of C18, PSA and Z-Sep+ was optimized using a mixture design approach and samples were analysed using gas chromatography mass spectrometry. The method was validated using trahira samples and a scope extension was performed for tilapia and tainha. Recoveries were within 63-129%, relative standard deviation was ≤21.5% and the quantification limits were 5 µg kg-1 or 10 µg kg-1. The applicability of the method was assessed by analysis of fourteen real samples, in which residues were detected in four samples. Such detections demonstrate the importance of this sensitive method.
DEVELOPMENT OF EXTRACTION PROCEDURE FOR ANALYSIS OF SEDATIVES AND β-BLOCKERS IN SWINE KIDNEY. A p... more DEVELOPMENT OF EXTRACTION PROCEDURE FOR ANALYSIS OF SEDATIVES AND β-BLOCKERS IN SWINE KIDNEY. A procedure was developed for determination of 5 sedatives and 14 β-blockers in swine kidney and subsequent analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Three different procedures for extraction were tested, evaluated through recovery studies. The procedure using acetonitrile for extraction and cleanup with freezing at low temperature and dispersive solid phase extraction using 500 mg celite ® 545 before the concentration step presented the better results. The dried samples were redissolved with methanol and analyzed using a LC-MS/MS system with electrospray ionization (ESI) operating in positive MRM mode. The recovery values for this procedure were in the 75-88% range. The robustness of the method was tested against small variations. The method was used to analyze carazolol, azaperone and azaperol in collaborative assay, obtaining results close to designed value.
A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea... more A method was developed for the analysis of 22 antiparasitic residues belonging to the benzoylurea, organophosphate, pyrimidinamine, pyrethrin and pyrethroid classes in salmon by liquid chromatography coupled with tandem mass spectrometry. Samples were extracted with acetonitrile-water as the extraction solvent with use of a vibrational shaking apparatus with a ceramic homogenizer. After extraction, the acetonitrile extracts were cleaned up by incubation at low temperature (-20°C, 1 h) to remove fat, followed by dispersive solid-phase extraction using Z-Sep+ and primary-secondary amine as sorbents. Validation was performed following the 2002/657/EC and SANTE/11813/2017 guidelines. The trueness of the method ranged from 87% to 121% and precision ranged from 4.1% to 23.7%, with the exception of cyphenothrin, dicyclanil and azamethiphos. The method developed is particularly advantageous because the use of a vibrational shaker allows unattended extraction of samples and eliminates a laborious tissue disruption step, which increases sample throughput in the laboratory. The sample preparation and chromatographic separations can be performed in 5 and 4 h, respectively, for 36 samples.
In this work, a method was developed, validated, and applied to determination of ten pesticide re... more In this work, a method was developed, validated, and applied to determination of ten pesticide residues (trifluralin, carbofuran, chlorothalonil, pendimethalin, captan, tebuconazole, pyraclostrobin, difenoconazole, deltamethrin, and azoxystrobin), from seven distinct classes, in carrot samples, employing a QuEChERS procedure for the analyte extraction and gas chromatography coupled to mass spectrometry (GC-MS) for quantification. The dispersive clean-up step was optimized using different sorbents at different concentrations and mixings. The method proved to be efficient and robust, showing recoveries in the range 72-117%, and RSD ranging from 4.9 to 16.6% (except for chlorothalonil and captan) at fortification levels of 45, 90, 180, and 450 μg kg −1 with seven replicates analyzed for each level (n = 28). Chlorothalonil and captan could not be validated due to analyte stability problems. Detection limits were between 15 and 45 μg kg −1 , and the quantification limits were between 45 and 90 μg kg −1. The method was successfully applied to real samples.
In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cro... more In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cropping, was assessed. Water consumption wells and surface water flows were sampled at different times. After a preconcentration step with solid phase extraction (SPE), the selected pesticides were determined by gas chromatography with electron capture detection (GC-ECD) or high performance liquid chromatography with diode array detection (HPLC-DAD). No pesticides were detected in the well water samples and surface water flow in the winter season. However, in the spring and summer higher concentrations of chlorpyrifos and imidacloprid were found in the water source samples. Atrazine, simazine and clomazone were also found. The occurrence of pesticides in collected water samples was related with the application to tobacco.
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