Does anyone have experience of using a Perkin Elmer Autosystem XL with prevent. I am trying to analyse Phenol in Water by Extraction into Iso Propyl Ether and analysis by GC. I am using the prevent technique but end up either venting everything or having too large a solvent peak due to insufficient venting. Any advice would be greatly appreciated.
By Mark on Friday, April 27, 2001 - 11:47 am:
With a PE Autosystem XL and HS40 we finally got some decent sensitivity using a 0.53mm column. But hydrocarbon peaks tailed badly. Took out the PreVent and got GREAT resolution and even better sensitivity. Makes you wonder if PreVent ever really worked all that well, or just for certain specific apps, or is just impossible to dial-in properly.
By jclark on Friday, April 27, 2001 - 12:56 pm:
You must have flow from your PreVent zone throughout the whole run. One of the tricky things is to optimize it. The pressure in the prevent zone when it is "closed" or "off" must be above the pressure in the column. Otherwise the column flow will go out through the prevent fitting. However, it must be just barely higher than column pressure in order to avoid causing turbulence, band broadening and tailing. This takes some trial and error after you've initially set it where it seems like it ought to be.
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