QuEChERS is an acronym for (Quick, Easy, Cheap, Effective, Rugged and Safe). It is a fast, easy, cheap, effective, robust and reliable multi-residue extraction method used for preparing fruit and vegetable samples for pesticide analysis. It combines two steps.
- The Extraction Step: The sample is extracted with acetonitrile and various salts. Internal standards may be used to check the analyte recoveries.
- The Dispersive Step (Solid Phase Extraction (SPE): The clean-up of an aliquot of the extract resulting from the previous step is carried out. For this clean-up phase PSA (SPE adsorbent ) and magnesium sulfate are used. The chromatographic analysis of the samples may now be carried out.
In comparison with previous extraction methods QuEChERS offers:
1 - Greatly increased speed of sample preparation
2 - Significantly reduced cost of materials
3 - In a single method more than 300 pesticides can be identified.
4 - Pre-weighed kits bring greater convenience, accuracy and speed.
No. It was developed originally as a method for the extraction of pesticide residues in fruit and vegetables but QuEChERS today is also being used to extract many compounds from a wide variety of matrices.
Work has already been carried out with QuEChERS using other matrices: products of animal origin (meat, fish, kidney, chicken, milk, honey), cereals, wines, juices, coffee, tobacco, soils, as well as fruit and vegetables.
In recent years, numerous research groups around the world have employed QuEChERS expanding its range of application, for example in the analysis of natural contaminants, antibiotics, veterinary drugs and mycotoxins amongst others.
No. Since its introduction, QuEChERS has been slightly modified according to the matrix or the compounds to be extracted. Today, new modifications continue to emerge improving sample preparation for the analysis of a wide range of analytes and matrices. Due to the large number of QuEChERS methodologies published one could say that it is more a technique than a methodology strictly speaking.
ExtraBond® QuEChERS EN-A is a variant of the European method EN 15662:2008. The main difference is the volume of the aliquot taken from the extraction step to introduce to the dispersive step. It has been shown with this modification that 4 ml of aliquot is sufficient to obtain the same results. Therefore, the amounts of PSA and magnesium sulfate have been reduced in the dispersive step resulting in a reduced kit price.
The dispersive Kit2A, Scharlau ref. QUDISENAK2, contains a small modification to the European EN 15662 method. The amounts of PSA and magnesium sulfate have been reduced since it has proved possible to work with a smaller extract volume (4 ml only) producing the same results. That is, the same results are achieved with a smaller amount of phase and therefore the kit price has been reduced.
In addition to our in-house research, our kit has been used by several reference customers, in the world of pesticide analysis, such as, “Analytica Alimentaria de Almeria” or “Lab. Agrario de Valencia” amongst others, validating our modification.
Sachets are used for several reasons:
-The sachets are more appropriate for the QuEChERS method than the centrifuge tubes. The contents of the sachets are poured into a 50 ml centrifuge tube containing the sample just at the right time according to the QuEChERS methodology , i.e., when acetonitrile is added to the sample. When using centrifuge tubes instead of sachets, the tube containing the mixture of salts must first receive the sample and then acetonitrile. This can result in exothermic reactions that can impair recovery. With the sachets these exothermic reactions are avoided and higher recoveries are obtained.
-The sachets are more convenient than the centrifuge tubes. The contents of the sachets are easily poured into a 50 ml centrifuge tube.
-The sachets ensure better conservation of the salt mixture than the centrifuge tubes.
Scharlau’s Kit-1A, extraction step, sachets are provided instead of tubes more appropriate for the QuEChERS methodology. (See question 1 above)
Scharlau Kit-2A, dispersive step is cheaper because it contains a smaller amount of phase. The same results are achieved with less phase resulting in a kit price reduction (see question 2)
Kit-2A Tubes are the only ones on the market that have the type of kit and the batch number printed on each tube for greater traceability.
The use of other solvents is not recommended because extraction is much more effective with acetonitrile. It has been tested with other solvents with unsatisfactory results; there are compounds that are not extracted equally well with methanol, and ethyl acetate is too volatile.
All dispersive kits contain MgSO4 and PSA. The MgSO4 remains water while the PSA removes organic acids, natural dyes and other impurities. In the case of samples rich in fats and waxes, the use of a kit containing C18 is recommended, while the graphitized carbon is responsible for removing the pigments.