Chromatography Forum

Running VOC methods (EPA 524.2/624.1/8260C). Recently the recoveries for the surrogate compound 4-BFB have been erratic. Have cleaned the MS source, cleaned the MS transfer line and trimmed 10 inches off the trailing end of the column. This has not corrected the issue. If someone has an alternative suggestion on how to address the problem, would be much appreciated. Not much literature out there on the subject.

Thanks

https://www.restek.com/pdfs/59887B.PDF

A very good guide to working with purge and trap. I got this many years ago in a mailing from Restek before the internet was something we had access to But it is still accurate even today. There are tons of other publications on their website on the subject also.

If you are having erratic recovery of a later eluting compound like BFB then you could have a low purge gas flow rate through the sparger, or the trap is not heating correctly and it is too cold to release the higher boiling components. BFB doesn't normally break down, but can be lost if there are problems with purge flow, heating, or contamination in the purge flow tubing. Do you have good recovery of the lighter components? Also are you looking for any compounds that elute after BFB and if so do those recover well?

Hi James,

The lighter compounds recover well. On checking the purge flow, it did turn out to be significantly lower than the proper rate. I adjusted it back to 40 mL/min and am running a series of washes with 4-BFB overnight. If the recoveries haven't stabilized, will look at the trap heater as you mentioned, or even further on down the line, water management if needed.

Thanks for the suggestion,
Walter

Don't overlook the inlet.
Could you include the specifics of your system? Trap,temps., liner, flows, how P&T connected to the GC.