Chromatography Forum

https://www.restek.com/Technical-Resour ... AR3314-UNV

Has anyone seen this before? I just got their email about it and it looks interesting. I don't think it will be accepted by EPA for environmental testing anytime soon but it would be interesting to try.

They presented on that at Pittcon in March. Seemed really interesting. Seems as though they're really pushing it to be the next big thing in chromatography. I suppose we'll see.

If I'm reading correctly, it looks like sort of analogous to SPME for samples not amenable to GC. Of course you're cutting out the LC entirely, which is something I see as an overall positive

Going on the SPME though-I've never been comfortable doing quantitative work with SPME, but it's one of my favorite ways to do quick and dirty quantitative analysis.

Interesting approach by Restek. This is the first I've heard of it. Thanks for the tip.

In my hands, SPME has been great for quantitation. I use it all the time. I will say that I think it really shines when you're looking for small concentrations of analytes. That's the "lions share" of what I do. I generally make sure I'm calibrating in the matrix because what else is present, can have a huge impact on how the analytes partition into the coatings.

I've had more difficulty when I'm trying to quantitate things present at percent-type concentrations. I will always go a different way for those kinds of things.

Interesting approach by Restek. This is the first I've heard of it. Thanks for the tip.

In my hands, SPME has been great for quantitation. I use it all the time. I will say that I think it really shines when you're looking for small concentrations of analytes. That's the "lions share" of what I do. I generally make sure I'm calibrating in the matrix because what else is present, can have a huge impact on how the analytes partition into the coatings.

I've had more difficulty when I'm trying to quantitate things present at percent-type concentrations. I will always go a different way for those kinds of things.

At percent levels I would either do dilute and shoot or headspace with high split. SPME and Purge and Trap are normally for trace analysis using the adsorbents to concentrate the sample.

I can see these blades working where you have analytes without many interfering signals but with a lot of physical matrix to eliminate, especially something like a soil sample. Not sure how well it would work for something like pesticides in Hemp, because there was always so much noise in the baseline on those samples from co-extracted analytes, if not separating it with LC you would need very high mass resolution to identify true positives.

Looks interesting, but I won't be spending a lot of cash on it speculatively. For even a very semi-quantitative view, they're going to have to show that it doesn't suffer from ion suppression effects. Good surface selectivity should help (though the more you rely on good surface chemistry to make a technique work, the more consistent you have to make the chemistry...).

It's vaguely reminiscent of SELDI technique, but without the MALDI-element. A sort of cross between this and the handbag-swab testing in airports?

I have mixed feelings about abandoning chromatography. Nowadays unless you can get all your samples onto a single plate Maldi-style, it's likely the chromatography won't be the time-limiting factor (and if you did get all your samples on a single plate, it's quite probable you've spent as much cash on robotics as you did on your MS). It takes longer to wash a needle and draw a sample than it does to do chromatography. That's why Agilent's multisampler comes with duplicate needles. And if you can do a bit of chromatography, even very roughly, it really helps the MS: just getting the salts and gunk away from the analytes is a massive benefit, and separating high- and low-abundance analytes a little can also help many mass specs get better spectral quality for the low stuff.

It all comes down to how many samples you have. With the improvements to automation and HTE techniques chromatography starts to take a substantial amount of time relative to other steps. E.g. if takes 3-5 days to synthesize 1536 reactions it then takes more than 2 days (and nights) to analyze all of them (let's say 2min per injection using UPLC)*. So if we take 5-7 days per such experiment - saving 1 day does make a difference. I see many efforts to make this cycle shorter. Though a lot of those efforts seem (I'm not an expert to judge) to end up being compatible only with some subset of chemistry/biology.

That's why Agilent's multisampler comes with duplicate needles.

And also can skip washes allowing MISER runs. Though I haven't seen anyone doing this for real yet.

*Of course it then takes time to go through chromatograms, but this time varies so much. I don't know how to include it in the calculations.

The only thing is, how long does it take to load the blade and start the next sample? If you can do injections into the HPLC at 2 minutes per sample, then you will have to be able to switch these out at fast. And you would need something to hold 100 blades before reloading or the autosampler on the HPLC will be faster.

The one advantage is you will not have to worry about contamination of columns by dirty samples, but on the other hand you no longer have the column to capture contaminates that might make it into the MS.