Are all polymeric solid phase extraction (SPE) sorbents created equal? | Trust your Science 5


What do we got on the inbox today for myths?
I’m excited! We have a lot of questions, but
there’s one that’s kind of interesting. It’s a little different than what
we’ve been looking at lately. So this particular scientist wants
to know about sample preparation. So what we do to the sample before it goes
into the liquid chromatograph. I don’t know much about that Kim! So they are looking to… …simplify their sample preparation
a little bit and they think or they want to know, rather,
if all polymeric solid phase extraction sorbents are water wettable
so they can skip some steps. So this is SPE, huh? Yes. Outside of my comfort zone, but I’m excited
to take a look at this myth! All right. So for this one, I think what we should do is take a bunch of different polymeric solid phase extraction sorbents, and run the same analyte on them. Okay. And since they specifically want to know
about water wettability I think we should try them with
conditioning and equilibration steps, which are included in traditional solid phase extraction, but then also try them without the
condition and equilibration steps to see if there’s any performance difference. Okay. We should look at recovery. We should look at reproducibility. Wow! And then we can determine, I think, whether this myth is true … or not. So you’re talking about before we put the analyte into the blue boxes? We gotta give something to them. Yes, we do. You can’t just take a piece of pizza
and stick it into the LC. It doesn’t work that way. You have to do something
to get the extract out of the pizza. Okay? Yeah, let’s do it. Okay, let’s go! All right Kim, well, let’s recap what we did with these little 1 CC cartridges here. Sure. So what we did was we tested four different polymeric solid phase extraction sorbents to see if there are water wettable. So we ran each one in triplicate… That’s right. … and we ran them with the condition and equilibration steps
to properly wet the sorbent first, and then we ran in a separate experiment where we ran them without the
condition and a equilibration, and we also ran them under extended vacuum, to see what degree those solid phase extraction sorbents would be wet. Great. And we should be able to tell from the data
whether or not the sorbant is truly water wettable
even though it’s polymeric. Let’s go. Look at the data. Let’s go. Okay. I gotta say that was pretty awesome. I mean I couldn’t even spell SPE to be quite honest. I’m glad to say instead of using pizza,
we use plasma. I’m glad we didn’t use the pizza. I liked it for lunch. But again, we got the results. I learned a lot about sample prep, and let’s walk through these results real quick. Yep, let me show you what we got. So we can see in these results. We took a look at four different polymeric SPE sorbents and what we did here was we did the traditional protocol that you would use where we used condition and equilibration you typically use condition and equilibration to wet the sorbets first. And we can see that all of these
sorbents worked pretty well. We have high recoveries.
They’re pretty reproducible. But the real point of this was
to test water wettability, right? So in our second experiment,
we ran these same sorbents without the condition and equilibration steps. I remember that. And what we can see here is that one of the sorbents worked really well, which would indicate that it’s truly water wettable but the other three did not. They have much lower recoveries, and – a big problem here is that they have much greater reproducibility issues – these error bars, the RSDs, were a lot higher here. Yeah, I can clearly see that. I mean the one that’s 100% water wettable performed much better than the other ones. Right. You can imagine how this might play out, too, when you’re doing an experiment in the lab, right, as you saw when we were in the lab… you’ve got the wells or cartridges
flowing at different rates So if one’s just drying out under vacuum or positive pressure, you might have the same kind
of problem with reproducibility. All right, Kim. This has been really
cool myth because, again, I’m learning a lot about SPE here. So what do you think really
makes one of these phases water wettable? So that’s a good question. And what we can see here if we look at
Oasis HLB, for example, that is actually a true copolymer. It’s made of n-vinyl pyrrolidone
and di-vinyl benzene. It’s stable over the whole pH range of 1 to 14. But the real key here is that it has this polar hook and it has a hydrophobic retention and what that enables it to do
is be truly water wettable. So it grabs onto that water and it doesn’t dry out. Actually in another experiment,
we tried drying the sorbant out We let it dry under vacuum
for half an hour and it didn’t dry out. Oh, wow. So there’s a big difference in performance. And it’s it’s safe to say that not all polymeric SPE sorbents are created equally. Yeah, I can see that for sure. All right Kim. So let’s try to
bring this back home here. So the original myth was are all
polymeric SPE sorbents water wettable? So I think I’m going to
split my answer on this one. Yep. And say it’s not true that
they’re all water wettable. But some are. So it’s important to know
which one you’re dealing with, and make sure that it is water wettable because that’ll give you the highest degree of reproducibility and performance. So, how do you want to call this myth? I’m gonna call it part true, part busted. Whoo. So how about – plausible? Plausible. I like that. If you’d like your question
to be answered on a future episode Please feel free to email us at
trust your science [at] waters.com.

Leave a Reply

Your email address will not be published. Required fields are marked *