We run the denitrifier method in Liverpool. We follow the same setup from the Updates paper by McIlvin & Casciotti, 2011. This is pretty much the go to guide. Regarding our timings; Trap 1 is down from 0 to 860 seconds, and Trap 2 is down from 800 to 1600 seconds, this is plenty of time to cryofocus the samples. The overall run time is set at 1900 seconds so about 31 minutes. This gives plenty of time for the column to be backflushed and prevents carry over between samples; although I'm sure you could get away with a couple of minutes less after the sample peak has come through if you don't have a carry over issue.
The main issue we had when setting the method up was carry over between samples. This was solved by installing a backflush. The backflush uses a shorter pre-column as it is not feasible to backflush the main column within the time frame. We also started baking the column for about 1hr @140 degrees before each sample run and ran N2O zero enrichments until the standard deviation returned to acceptable levels. This improved the precision of the method.
University of Liverpool