Frequently Asked Questions (FAQ) About QuEChERS Method
1. How can QuEChERS benefit work? (matrix removal and analyte extraction)
The QuEChERS method is a generic sample preparation technique that focuses on matrix removal. Since the QuEChERS method is not analyte-specific, you can prepare samples for analysis of various compounds without spending any time on method development.
2. How long does the QuEChERS program take? (time)
For 25 to 30 samples, the actual extraction and SPE purification process should take no more than 90 minutes. The time-limited step is to weigh the sample into a 50 ml centrifuge tube during the extraction step.
3. Are QuEChERS compatible with my work? (sample preparation selection)
If you want to eliminate matrix noise, the QuEChERS approach is for your work. The technique is particularly effective for solid, semi-solid, viscous liquid mixtures and small amounts of liquid samples.
4. Compared to other food sample preparation techniques – is it expensive?
Not at all. Each sample will cost a few dollars. The QuEChERS approach allows you to use less hazardous solvents in smaller volumes, which eliminates the cost of hazardous solvent disposal and general bulk solvent disposal. At the same time, you will get a better sample purification effect and will help extend the service life of the analysis column and save the cost of purchasing a new column.
5. How to select the appropriate kit for the QuEChERS method?
Select the kit according to the nature of the sample. The MgSO4 / PSA kit can be used for high-water, light-colored, fat-free samples such as apples, oranges, and lettuce. MgSO4/ PSA/C18E kits can be used. These samples are rich in fat and wax, but only light-colored samples, such as coconut, avocado, nuts, and seeds. The MgSO4/PSA/GCB kit can be used to sample colored and low-fat samples (e.g. spinach, berries, chilies). MgSO4 /PSA/GCB/C18E can be used for samples rich in pigment and fat, such as chocolate and black olives.
6. I am not bound by AOAC or EN standards. Which extraction kit should I choose?
Any buffer extraction kit can be used if a large number of pesticides or target analytes are pH dependent. Use the original non-buffering kit, if there are only a few compounds or the target analyte is not pH dependent.
7. What is the difference between AOAC and EN QuEChERS?
Both are buffered and are different from the selection of buffer salt in the extraction step and the sample to the salt and adsorbent ratio in the dispersion purification step.
8. Under what circumstances would you choose a 1 ml QuEChERS kit and an 8 ml kit?
To use bulk injection for GC/MS in the lab, the 1 ml kit is suitable and an 8 ml kit requires concentration of the final extract and exchange of the solvent into toluene for GC/MS to enable detection of 10 ng/g pesticides.
9. What is the role of magnesium sulfate in the extraction and dispersion purification process?
During extraction and purification, add the magnesium sulfate to absorb water and also increase the aqueous mixture’s ionic strength, and initiate phase separation from acetonitrile.
10. My QuEChERS analysis included a fair amount of acidic pesticides. Does PSA reduce its recovery? What changes can I make?
PSA adsorbents may retain acid analytes. If this is a problem, you can omit the dSPE step and directly analyze the supernatant in the extraction step. You can also use PSA to compare results with and without dSPE to determine whether the PSA purge is appropriate for your sample.