Chromatography Forum

Dear all,
I have to measure trace of benzene in pure, pharmaceutical grade, acetone. My target is limit of 2 ppm of benzene. European Pharmacopeia describe a GC method that is: FID, column 50 m, 0.3 mm ID, 1 um film, stationary phase macrogol 20000R, split ratio 1:50, inj 1 ul.
With this method I should reach my low specification. I've already tried to make some tests with similiar method (FID, 0.53, HP-innowax, 1 um, 30m, spliut and splitless) but I can't reach this low level.
Can someone help me? Do you think that with the exact EP column I can reach 2 ppm level? Any suggest will be usefull.
Thank you very much.

The simple answer is "yes", you should be able to see 2ppm benzene using an FID, especially in the splitless mode. Optimize your carrier gas flow, gc temperature program, gas flows to the FID, and/or replace the FID jet (make sure you are using one with the correct ID tip).

You may have an installation problem where you are discriminating the sample and are not getting a representative sampling of the benzene present.

Just a possibility.

Rod