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Sample Prep and Analysis
- New free-flowing salts in slim packs make extraction a snap.
- Complete line of easy-to-use QuEChERS products, reference standards, and accessories.
- Follow up sample prep with a wide range of analytical columns for both LC and GC.
Keep your workflow running smoothly with Q-sep extraction salts from Restek!
For years, the QuEChERS approach to sample preparation has been making the lives of food safety scientists easier. Gone are the days of time-consuming, solvent-intensive extraction techniques and multiple solid phase extraction cartridge cleanup steps! Research published by the U.S. Department of Agriculture Easter Regional Research Center in Wyndmoor, PA,  introduced to the world QuEChERS—a method that is Quick, Easy, Cheap, Effective, Rugged, and Safe.
With QuEChERS, a homogenized sample undergoes a quick extraction step where the analytes are driven into an organic solvent by the partitioning power of a blend of salts. After extraction, the sample is cleaned up through the use of a dispersive solid phase extraction (dSPE) step that is also quick and easy to perform. This simple, two-stage process offers significant savings in time, materials, and effort, making QuEChERS sample preparation faster and easier than other approaches.
Table I: Prepare samples more quickly, easily, and cost effectively with QuEChERS.
Since its introduction, the QuEChERS technique has evolved to accommodate an expanding list of pesticides in an increasingly diverse list of foodstuffs. At Restek, we offer Q-sep products to cover the four major approaches to QuEChERS, along with a host of other items to help make your QuEChERS experience simple and successful. We carry a comprehensive line of sample prep supplies, reference standards, and LC and GC columns that will help make QuEChERS even easier, whether you are new to the approach or developing a method for a new sample matrix.
Which product do I choose?
QuEChERS is primarily a two-stage process, and you’ll select Q-sep products for both stages. Your method may have specific recommendations, but in case you’re not sure what will work, here are some considerations when making your selection.
Stage 1: Extraction
The choice of which extraction technique to use is made principally by considering your analytes of interest. If you’re looking for compounds that aren’t pH sensitive, the original unbuffered method  will work great. However, if your analytes of interest are pH sensitive, you will want to select one of the buffered methods—notably, the official EN 15662 method , the mini-multiresidue approach , or the official AOAC 2007.01 method .
Restek’s Q-sep products for the two European approaches, the official EN 15662 method and the mini-multiresidue approach, are the same, so it becomes essentially a choice between a European-developed method and the AOAC method. Both are buffered to lower the pH to a range where most pesticides are stable, and the methods differ only in the specific buffering salts and their ratios. Either would be a good place to start for most analyses. There are a great many studies that highlight specific instances when one buffering technique may outperform another, so a little research into your particular area of study may yield practical suggestions on which extraction method to use.
Stage 2: Dispersive Solid Phase Extraction (dSPE) Cleanup
The next big choice comes during the selection of which dSPE cleanup product to use. Where the choice of the extraction product was driven largely by the analytes of interest, the choice of cleanup is based on the sample being tested. Restek Q-sep dSPE products are formulated with different sorbents in different ratios so that your dSPE choice can be tailored to the composition of your particular sample type (e.g., fatty, highly pigmented, etc.). Use Table II to learn what each sorbent removes and to help select the best dSPE product for your particular sample.
Table II: Visit the desktop version of www.restek.com/quechers to access this table.
Table II: Select your dSPE tube based on sample type to ensure you get the best sorbent blend for removing specific matrix interferences.
|Method||Sorbent Mass (mg)
|MgSO4||PSA*||C18-EC||GCB**||Vial Volume (ml)
|Excess Water||Sugars, fatty acids, organic acids, anthocyanine pigments||Lipids, nonpolar interferences||Pigments, sterols, nonpolar interferences|
|General fruits and vegetables (e.g., celery, head lettuce, cucumber, melon)||AOAC 2007.01||150||50||-
|Original unbuffered, EN 15662, mini-multiresidue||150||25||-||-||2||26215|
|Original unbuffered, EN 15662||900||150||-||-||15||26223|
|Foods with fats and waxes (e.g., cereals, avocado, nuts, seeds, and dairy)||Mini-multiresidue||150||25||25||-||2||26216|
|Pigmented fruits and vegetables (e.g., strawberries, sweet potatoes, tomatoes)||Mini-multiresidue, EN 15662||150||25||-||2.5||2||26217|
|Highly pigmented fruits and vegetables (e.g., red peppers, spinach, blueberries)||Mini-multiresidue, EN 15662||150||25||-||7.5||2||26218|
|General purpose (wide range of commodities, including fatty and pigmented fruits and vegetables)||-||150||50||50||7.5||2||26243|
Note: No entry in the Method column refers to dSPE formulations not specifically included in one of the cited references. These products can be used to accommodate the various needs of specific matrices not directly met by the cited references.
*PSA = primary secondary amine exchange material
**GCB = graphitized carbon black
Restek is not able to provide copies of these documents.
 M. Anastassiades, S.J. Lehotay, D. Stajnbaher, F.J. Schenck, Fast and easy multiresidue method employing acetonitrile extraction/partitioning and "dispersive solid-phase extraction" for the determination of pesticide residues in produce. J. AOAC Int. 86 (2003) 412-431. http://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=555&content=PDF
 EN 15662, Foods of Plant Origin—Determination of Pesticide Residues Using GC-MS and/or LC-MS/MS Following Acetonitrile Extraction/Partitioning and Clean-up by Dispersive SPE—QuEChERS method, 2008.
 QuEChERS-A Mini-Multiresidue Method for the Analysis of Pesticide Residues in Low-Fat Products, 2004. http://quechers.cvua-stuttgart.de/pdf/reality.pdf
 AOAC Official Method 2007.01, Pesticide Residues in Foods by Acetonitrile Extraction and Partitioning with Magnesium Sulfate, 2007.
low-polarity phase; Crossbond 1,4-bis(dimethylsiloxy)phenylene dimethyl polysiloxane
Sturdy, easy-to-clean FEP (fluorinated ethylene propylene) tubes last indefinitely under normal usage conditions—and cost 50% less!
Supplies & Accessories
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Featured Application: Multiresidue Pesticide Mix Extracted from Brown Rice Flour Using QuEChERS Extraction and Cleanup - 7.5-Min Screening Analysis of Multiresidue Pesticides in Brown Rice Flour
Multiresidue pesticides analysis presents many challenges, from extensive lists of chemically diverse analytes to the negative effects of complex matrix components. The optimized chromatographic method described here allows the analysis of hundreds of compounds in as little as 7.5 minutes with a total cycle time under 10 minutes, ensuring fast, accurate sample screening and increased lab productivity.
Evaluation of Dispersive and Cartridge Solid Phase Extraction (SPE) Cleanups for Multiresidue Pesticides in QuEChERS Extracts of Finished Tobacco Using GCxGC-TOFMS
We compared the efficacy of dSPE and cSPE cleanup methods for multiresidue pesticide analysis of QuEChERS extracts of finished tobacco products using GCxGC-TOFMS. Cleanup with dSPE tubes containing 7.5 mg of GCB and 25 mg of PSA produced better results than other methods, with average recoveries of 92% and 91% for 500 ppb and 50 ppb fortifications respectively.
Comparing Pesticide Residues in Amish and Commercially Grown Strawberries and Spinach Using QuEChERS, Various dSPE Sorbents, and GC-TOFMS
QuEChERS extraction, dSPE cleanup, and GC-TOFMS analysis were used to assess pesticide residue levels in strawberry and spinach from both commercial and Amish growers. Various dSPE sorbent products were compared to determine which were most effective.
Learn how to use the QuEChERS approach to perform faster, easier sample preparation and cleanup for multiresidue pesticide analysis. Q-sep QuEChERS products save time, money, and materials compared to modified Luke methods. (PDF - 5MB)
Not all column deactivations are appropriate for analyzing basic compounds. Here, we demonstrate the effect of column inertness on peak shape and discuss its role in improving method accuracy, sensitivity, and development time. (PDF - 0MB)