SPME Fundamentals: Liner Selection for HS VOCs

My colleague Linx Waclaski is usually the one doling out excellent liner advice, so bear with me as I take a crack at this liner stuff. Ever since we came out with traditional SPME and the SPME Arrow, a lot of customers have had concerns/questions regarding SPME liner dimensions. The short answer to most of these questions is that none of this “makes a tinker’s dam” (an old expression my dad used to say to me, so as to let me know I was focusing in on inconsequential minutia) for head space (HS) volatile organic compounds (VOCs). Look up tinker’s dam for a fun fact. If you want the long answer (with appropriate caveats), turn to page 36 of the following:

The Column (17 December 2018 Volume 14 Issue 12)

I really wrote the current blog and the above article for the new traditional SPME and/or SPME Arrow end user. In particular, to let them know they need not get wrapped around the axle when it comes to liner selection. Oh, and to challenge the unsupported claims I see some vendors make that narrow bore inlet liners are more efficient for SPME.

If you are interested in moving the needle significantly, there a far more important details surrounding SPME extraction and desorption that deserve your precious time and consideration. In fact, the SPME end-user has over a dozen extraction and desorption conditions (e.g., extraction temperature, desorption duration, etc…) they can manipulate. For example, look at Colton’s recent blog on incubation/extraction temperatures for cannabis residual solvents using SPME. In particular, look at what happens when you incubate/extract at 30 vs 80°C for o-Xylene. Yes, I know it may be hard to see with the log scale. Luckily, I happen to share an office with Colton and can tell you that we are looking at average peak area responses of 1.66 x 107 vs 5.97 x 106, respectively. That is an 89% difference in response, without having to purchase different liners. Mind you, in the LCGC article I wrote the largest statistically significant difference we saw was only 57%. I hope you see the point.

I am not saying to ignore liner selection. What, I am saying is that there is only so much time in a day and I would encourage you to invest your limited time into optimizing the extraction/desorption conditions, as illustrated in Colton’s blog. So, stay tuned for some up-coming blogs where we continue to demonstrate which SPME parameters actually make a tinker’s dam.

2 Responses to “SPME Fundamentals: Liner Selection for HS VOCs”

  1. Paul Klette says:

    First thanks for this blog series. I like fundamentals. I read the linked article by Jason S. Herrington and got a few questions about it.

    1. Why is there a difference in peak area between the 0,75 mm and 2 mm liner? The Peak width should be wider for the 2 mm liner but the Peak area should be the same. (Degradation or lost in the split?)

    2. With a split of 1:5 the velocity in the inlet is much higher than with splitless injection. I can imagin with the higher velocity in the liner because of the split, the liner diameter is not that importent any more.

    3. Why the % RSD of the 2 mm liner seams to be better than for the 0,75 mm liner?

    4. Which role does the distance of the column to the liner Play in this case? (keyword tapered liner)

    I hope the community got some ideas.

  2. Paul,

    Thank you for the comment. Please be sure to check out the following response: https://blog.restek.com/?p=56969

    Kind Regards,
    Jason

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