marc engel - Academia.edu (original) (raw)

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Observatoire Midi-Pyrénées, Université de Toulouse III Paul Sabatier

STYLIANOS N . PASCHOS, PH.D., ESQ.

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Papers by marc engel

Research paper thumbnail of Multiresidue Analysis of Pesticides in Fresh Fruits and Vegetables Using Procedures Developed by the Florida Department of Agriculture and Consumer Services

Journal of AOAC International, Nov 1, 1999

Improved quality and efficiency of pesticide residue analysis were achieved by examining all aspe... more Improved quality and efficiency of pesticide residue analysis were achieved by examining all aspects of the laboratory process. In an effort to eliminate methylene chloride hazardous waste, an acetonitrile extraction method, originally developed by the California Department of Agriculture, was modified and adopted. Sample size and solvent consumption were reduced with the new method. Custom glassware racks and disposable supplies reduced overall analysis time. Gravity-fed, solid-phase extraction simplified sample preparation and provided cleaner extracts for gas chromatographic analyses. Modifications to the method were made to achieve the ruggedness needed to maintain quality objectives during routine analysis. Instrumental improvements, including new selective detectors, retention time locking, and mass spectrometry screening for all samples, provided the laboratory with efficient, reliable, and confirmed analytical results.

Research paper thumbnail of Multiresidue Screening of Pesticides in Foods Using Retention Time Locking, GC-AED, Database Search, and GC/MS Identification

Journal of AOAC INTERNATIONAL, 1999

Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with ato... more Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with atomic emission detection (GC-AED) and an experimental database. A technique called retention time locking was used to match GC-AED and GC with mass spectrometry (MS) retention times to those of the database. Samples were analyzed for sulfur, nitrogen, phosphorus, and chlorine by GC-AED. Possible pesticides were suggested by database search and identified by GC/MS. Forty-four pesticide standards were analyzed to determine the precision of retention time matching and the accuracy of the database search. Analytical retention times matched database retention times within 0.32 min. Using elemental criteria, the database search identified the correct compound for 41 of 44 pesticide standards. For blind spikes of fruit and vegetable extracts, the database suggested 22 of 26 spiked pesticides as matches. Nineteen were identified by GC/MS. The combination of retention time locking, GC-AED, database...

Research paper thumbnail of Symposium Introduction: 55th North American Chemical Residue Workshop

Journal of Agricultural and Food Chemistry, 2019

Research paper thumbnail of Origin determination of the Eastern oyster (Crassostrea virginica) using a combination of whole-body compound-specific isotope analysis and heavy metal analysis

Analytical Methods, 2021

A combination of amino-acid-specific isotope ratio mass spectrometry and ICP-MS of lead and cadmi... more A combination of amino-acid-specific isotope ratio mass spectrometry and ICP-MS of lead and cadmium helped discriminate the harvesting areas of the Eastern oyster, Crassostrea virginica, within the Gulf of Mexico.

Research paper thumbnail of Multiresidue Analysis of Pesticides in Fresh Fruits and Vegetables Using Procedures Developed by the Florida Department of Agriculture and Consumer Services

Journal of AOAC International, Nov 1, 1999

Improved quality and efficiency of pesticide residue analysis were achieved by examining all aspe... more Improved quality and efficiency of pesticide residue analysis were achieved by examining all aspects of the laboratory process. In an effort to eliminate methylene chloride hazardous waste, an acetonitrile extraction method, originally developed by the California Department of Agriculture, was modified and adopted. Sample size and solvent consumption were reduced with the new method. Custom glassware racks and disposable supplies reduced overall analysis time. Gravity-fed, solid-phase extraction simplified sample preparation and provided cleaner extracts for gas chromatographic analyses. Modifications to the method were made to achieve the ruggedness needed to maintain quality objectives during routine analysis. Instrumental improvements, including new selective detectors, retention time locking, and mass spectrometry screening for all samples, provided the laboratory with efficient, reliable, and confirmed analytical results.

Research paper thumbnail of Multiresidue Screening of Pesticides in Foods Using Retention Time Locking, GC-AED, Database Search, and GC/MS Identification

Journal of AOAC INTERNATIONAL, 1999

Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with ato... more Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with atomic emission detection (GC-AED) and an experimental database. A technique called retention time locking was used to match GC-AED and GC with mass spectrometry (MS) retention times to those of the database. Samples were analyzed for sulfur, nitrogen, phosphorus, and chlorine by GC-AED. Possible pesticides were suggested by database search and identified by GC/MS. Forty-four pesticide standards were analyzed to determine the precision of retention time matching and the accuracy of the database search. Analytical retention times matched database retention times within 0.32 min. Using elemental criteria, the database search identified the correct compound for 41 of 44 pesticide standards. For blind spikes of fruit and vegetable extracts, the database suggested 22 of 26 spiked pesticides as matches. Nineteen were identified by GC/MS. The combination of retention time locking, GC-AED, database...

Research paper thumbnail of Symposium Introduction: 55th North American Chemical Residue Workshop

Journal of Agricultural and Food Chemistry, 2019

Research paper thumbnail of Origin determination of the Eastern oyster (Crassostrea virginica) using a combination of whole-body compound-specific isotope analysis and heavy metal analysis

Analytical Methods, 2021

A combination of amino-acid-specific isotope ratio mass spectrometry and ICP-MS of lead and cadmi... more A combination of amino-acid-specific isotope ratio mass spectrometry and ICP-MS of lead and cadmium helped discriminate the harvesting areas of the Eastern oyster, Crassostrea virginica, within the Gulf of Mexico.

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