Retention Times on PLOT columns

General discussion of factors that affect chromatographic resolution, peak shape, and noise in the raw data.
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White Rabbit
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Joined: Tue Dec 08, 2015 8:35 pm

Retention Times on PLOT columns

Post by White Rabbit » Thu Dec 17, 2015 4:35 am

We are seeing retention times shifting on our PLOT column even though we have ample flow on the nafion dryer and our dry gas source is bottled nitrogen which has both HC and moisture traps inline. The BP retention times are solid so I think it is related to moisture in the sample but not sure why. Anybody have any other suggestions?

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White Queen
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Joined: Tue Dec 08, 2015 9:21 pm

Re: Retention Times on PLOT columns

Post by White Queen » Thu Dec 17, 2015 6:33 am

We recently reviewed some of our RT data on the PLOT column and found that our RT stability for Propane gave us RSD values of 0.03 across 24 hours (hourly sampling). But we had the system stop for 3 days and when it was restarted it took almost 24 hours for the retention times to really stabilize. Ours is a Markes Thermal Desorber with an Agilent GC. We had seen similar issues with stopping and restarting systems when we were involved with some of the event triggered sampling. When we worked with event triggered systems which basically sat idle until a TNMOC analysis showed high values, when the system sampled and then ran a chromatogram after being idle the PLOT retention times were not stable. We had to run a retention time standard each time we had an event and even then we had to rely on pattern recognition and relative retention times to identify peaks because the change from run to run was so great when starting from idle.

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