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Expanded Applications of Quenchers to Food Environmental Samples


<ol> <LI> Expand the scope of food types analyzed at the CAES for pesticide residues using the Quick, Easy, Cheap, Efficient, Rugged and Safe (QuEChERS) extraction method: Over the past few years, samples of egg, olive oils, honey, candy, cookies, wafers, cakes, cereals, and baby formula powders have been analyzed in our labs for pesticide residues using the QuEChERS protocol. The proposed work will add different types of food matrices to this list. It is difficult to predict the matrices that will be analyzed as part of this work. The samples to be analyzed are provided by the Connecticut Department of Consumer Protection (DCP) as part of routine surveillance work and, as such, can vary greatly dependant upon need. <LI>Apply the methodology to the analysis of environmental samples: preliminary work in our labs has demonstrated that the QuEChERS method is suitable for the extraction of ortho-phenylphenol (OPP) from paper bag samples. The work has established an approach for validating the QuEChERS extraction method in a single environmental sample. We have successfully applied the QuEChERS method to extract cloth and shampoo samples. We envision that QuEChERS will replace our current methods for the extraction of pesticides from these matrices. It is further proposed that QuEChERS will replace our current method for the extraction of pesticides from soil and foliage samples analyzed on behalf of the Connecticut Department of Environmental Protection (DEP). <LI>Apply the methodology to the analysis of Polychlorinated Biphenyls (PCB's) in environmental samples: We currently analyze oil samples for PCB's by microwave extraction using 3:2 hexanes-acetone. We propose to replace this method by the QuEChERS method. </ol>Milestones: Year 1: Submission of two manuscripts. The first manuscript will be comprised of a comparative study of our older method for the extraction of pesticide residues from food samples with the QuEChERS extraction protocol. The vast majority of this work has been completed. The second manuscript will consist of the work on OPP in paper bags. This will contain a comparative study of the QuEChERS method with Soxhlet extractions. It will further demonstrate the transfer of OPP to fruit contained within the bag. <P>Year 2: Submission of a manuscript comparing the use of the QuEChERS method with that of our current microwave method for the extraction of PCB's from oil samples. This manuscript is anticipated to include some work on the extraction of pesticide residues from fish tissue. <P>Year 3: It is anticipated that over the course of the first two years of this proposal the DCP will continue to provide surveillance samples and that these samples will be analyzed by QuEChERS. In the final year of this work, a manuscript will be put forth describing the different food types which have been analyzed.

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Non-Technical Summary: The introduction of the QuEChERS protocol at the CAES has had numerous impacts on the analysis of food products which include 1) a realized savings in solvent use and disposal cost, 2) lower limits of detection of pesticide residues, 3) the detection of a wider array of pesticide residues, 4) the ability to analyze a wider array of matrices for pesticide residues, 5) greatly reduced the time needed for the extraction of pesticides from their inherent matrices. Our work has led to the recall of products not previously analyzed in our labs including infant cereal. The lower detection limits attainable through the use of QuEChERS have forced the EPA to re-examine tolerances of certain pesticides on certain crops. Future tolerance assessments by EPA may need to define a lower limit of pesticide residue allowable on food. Going forward, the application of the QuEChERS extraction protocol to non food substrates, in addition to realizing the above stated benefits, will reduce the total number of methods used by laboratory personnel. The knowledge gained by applying the method to environmental samples will benefit the entire environmental pesticide community as it did when QuEChERS was introduced for the analysis of residues in food. Widespread use of the QuEChERS method over a wide variety of substrates will lead to a huge reduction in solvent consumption which, environmentally speaking, benefits all mankind. <P> Approach: The proposed work involves comparing the amount of pesticide contained in QuEChERS extracts with the amount of pesticide contained in Soxhlet or microwave extracts of identical samples. This side by side comparison will provide information on the feasibility of replacing older methods with the QuEChERS method. The Soxhlet method involves placing a known amount of sample into an extraction thimble. The sample can be spiked at this point with pesticides of interest and an internal standard. Anhydrous sodium sulfate is placed on top of the sample to ensure continuous drying of the solvent. Solvent is refluxed onto the sample and drained back into the solvent reservoir repetitively (usually 50 - 200 repetitions). After cooling, the solvent is concentrated to a known volume into a concentrator tube and analyzed as appropriate. Microwave extraction involves placing the sample and extraction solvent into appropriate microwave safe vessels which are then sealed. The vessels containing solvent and sample are placed into a microwave oven. Microwave energy is used to release pesticides from their matrix into the extraction solvent. The microwave energy introduced into the system heats water present in the sample resulting in increased temperature. Because the extraction is carried out in a sealed vessel, the pressure on the sample also increases. Following extraction, the vessel and its contents are cooled to room temperature. The solvent recovered after the extraction is concentrated to a known volume and analyzed as appropriate. The QuEChERS method as published is highly generalized and open to modification depending on the requirements of the user and the analysis being performed. Briefly the method consists of three steps: 1) Weighing 15 g of sample into a 50 mL centrifuge tube to which 15 mL acetonitrile, internal standard, 6 g MgSO4 and 1.5 g NaOAc are added. The tube is shaken and centrifuged. 2) A portion of the extract is transferred to a 10 mL centrifuge tube containing 1.5 g MgSO4, 0.5 g primary-secondary amine (PSA) bonded to silica and 2 mL toluene. The tube is shaken and centrifuged. 3) A portion of the purified extract is concentrated under a stream of nitrogen. Analysis of all extracts will be performed by liquid and gas chromatography with mass spectral, electron capture or nitrogen phosphorous detection. Quantitation will be performed by external standard calibration. The use of an internal standard may be used as required. Comparison of the results obtained from the methods employed, as well as with the recoveries of any spiked standards, will determine if the QuEChERS method provides a viable alternative to those methods currently in use in our labs.

Krol, Walter
Connecticut Agricultural Experiment Station
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