Rxi Guard/Retention Gap Columns (fused silica) by Restek Corp.

"I've used the Rxi guard column for 3+ years connected to an Rxi-PAH 60m column. I've used this setup to analyze PAH levels in air samples from cookstove emissions. Originally, I used the Rxi-PAH column without a guard, and eventually purchased guard columns to extend the lifetime of the much more expensive PAH column. I think this setup has worked and even if it hasn't the guard column is very inexpensive. I do appreciate having a guard to trim instead of the PAH column, which means once I get that perfect cut on the PAH column I can install and forget it. However, my last 2 guard columns have not lasted as long as expected. They both snapped close to the GC inlet during sample runs despite not touching metal surfaces. This prolonged air exposure ruined both columns and the bleed was too much to continue using. I think that despite the temperature rating of 360C, it should be higher or it isn't correct. The guard column is more brittle than the PAH column after installation, and that makes clean cuts harder the longer I use. Additionally, the binding that holds the coils together is inadequate. The small strings come loose in the oven. And the coil out of the box is tighter than the PAH column metal holder, making it tough to wrap the coiled guard column around the main column. These things could be improved for the guard columns to make installation easier, because the toughest part is the first install getting the main and guard columns situated in the GC without too many loose lines touching metal surfaces."