Chromatography Forum

Something that has been in the back of my mind for 20 years or so.
How do bubbles affect results (if any) when using a needle type autosampler that moves sample via purge gas pressure.
We accept samples with bubbles <3mm and run them without qualification.
Our sampler (Aquatec 70) over pressurizes the vial durring sample transfer to the P&T, so I would think reasonable bubbles should not make a difference.
I never got around to doing a study on this question.
Any of you done a study? How do you deal with bubbles in a sample?

Thanks
Bear

As far as sample acceptance criteria, I believe you have to keep it as ,3mm bubble, since overpressuring the sample for a short period of time to transfer to the purge and trap would not be long enough to force any analytes that have moved into the headspace/bubble back into solution. The bubble rule is mainly for loss of analytes during storage.

It is compound dependent, as you would expect. You (for obvious reasons) lose the gases pretty quickly if you have bubbles. You also, for whatever reason, lose perchloroethylene. However, I kept some vials of plain ol' groundwater with about 5 mm of headspace sitting around the lab (not refrigerated) for 6 months that I had spiked with BTEX compounds and we were still getting recovery when we quit playing with them, so the loss of water solubles is pretty low.