QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) is a powerful and flexible sample preparation technique. As is often the case, some undesirable components can make it in to the extract. Dispersive solid phase extraction is often used to clean up these extracts. They come in many different configurations including different sizes, different sorbents, and different sorbent quantities. Here we share some information on how to make the best choice.
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Hi and welcome to this Restek Tip where we will talk about dispersive solid phase extraction. So you've just performed a QuEChERS extraction and chances are your extract needs to be cleaned up. And that's where dSPE or dispersive solid phase extraction enters the picture. When you go look for dSPE products you're going to find that they are defined principally by the size of the dSPE tube, the sorbents in the tube that will do the cleaning up, and how much of those sorbents are present. Now, that means that there are a lot of products to choose from, so how do you know which is right for you?
When it comes to the size of the tube, just think about what are you going to do with that cleaned up extract? If you're just going to take it and one tube makes one sample for one analysis, the smaller two milliliter tubes will be great. But if you need to split that cleaned up extract to be spread across multiple analyses, for instance, you may want to consider the larger 15 ml tubes. They will give you plenty of final volume to work with.
Now, for the cleaning up. The sorbents. Which ones do you need? You'll notice that all of the dSPE products have some quantity of magnesium sulfate and that's there to clean up any residual water that may still be in the extract after the QuEChERS extraction step.
Now, if your commodity, which is what's going to drive the sorbent that you need, has sugars or organic acids or fatty acids, you'll want to look for a dSPE product that has the primary secondary amine sorbent (PSA). That will do a great job of removing those from the sample.
Now, let's say your sample that you're analyzing is a fatty sample that has fats or waxes. You'll need something nonpolar to pull those out and that's where an end-capped silica coated with a C18 ligand, usually just called a C18 sorbent, will be perfect.
Now, finally, what if you have a highly pigmented sample? Your extract has lots of color. You'll want to get that out before analysis and that's where something like graphitized carbon black or GCB will do the trick. And, depending on how much of those different components are in your sample, you might want more or less of any given sorbent. And if you're just not sure, the great thing about QuEChERS is that it's relatively quick to give it a try. So, get a couple of products, see what works best at cleaning up your sample but not harming the recovering of your analytes of interest. So, good luck with your QuEChERS extraction and clean up and thanks for joining us for this Restek Tip!