SPME Injection

[npaz]

I was wondering if anyone has experience with GC SPME injection. I have gone through 3 fibers in the last two weeks. This seems to happen upon injection into the inlet. I thought that if the syringe was pulled out prior to the inlet purge it would work. Im guessing my inlet flow or pressure is too high or the septa is too thick ???

[MSCHemist]

I do it all the time. The fiber has to be in the protective sheath any time it passes through a septa. Just, hit prep run, stick it through the septa, extend the fiber, wait 1 min for desorption, hit start, then retact fiber and pull it out of the inlet. Also what liner are you using. At my last position we did extensive research and found a 1mm Restek 20973 liner with a 2:1 split works best.

The septa purge and purge valve should have no effect on the fiber.

[Don_Hilton]

If the fiber lost from the asembly? charred? bent?

I will not that a liner with a glass wool plug will remove the fiber from the wire that it should be attached to...

[Robert Van Hale]

May I add a question to this - what septa and needle do you use? I am having trouble with septa being blown out in just a few injections - using Supelco 24 Ga SPME assemblies with square points.

thanks
Robert

[MSCHemist]

I am not sure what needle I have. I use the 2cm Carboxen/DVB/PDMS fiber and Agilent green septa. I haven't really had any trouble with SPME at all. In fact I find it very convenient for dry starch encapsulated flavors. The only downside is there is some controversy as the whether SPME provides a representative composition of the sample when doing % reports and the precission isn't as good as liquids injection. However, any technique I sue will have issues especially with volatiles and with different response factors on the TIC.

[npaz]

Thank You for time and input on this topic. I will try that approach.