Chromatography Forum

Are +/- 20-25 seconds on a 60-70 minutes run acceptable as retention time reproducibility? Or should I start troubleshooting?

The compounds are 37 and thus the window for automatic peak identification shouldn't be to wide. I have trouble getting all peaks correctly identified. I am thinking about using a reference peak.

I would consider that unacceptable. If we run a FAME method that long, we're looking at resolution of cis-trans isomers on a 100-m column, where good chromatography and retention time stability is essential.

I would check to see if any loop of the column is touching the oven floor or sides.

Then either flow variation or heating variation is the problem. A leaking septum would be part of the flow checking.

Good luck,

Rod

What stabilization time do you leave the column run for? I am referring mainly to the first runs after 20-30 minutes of stabilization time.

I notice this.

The runs is approx. 1 hour long.

The peaks have a width of around 0.1min. more or less.

The closest two neighbouring peaks will get (when inj. the mix standard) is ~0.2min.

The FID and column are stabilized at initial program temparature for ~15-20mins.

The 1st run will yield ~0.4min. more Retention Time than the mix standard chromatograph I have run in the past for reference.

The 2nd, 3rd etc seem to stabilize to times closer to the mix standard's RTs. up to ~0.1min. differences.

To avoid this phenomenon and get the proper retention times that allow for proper recognition, would a short program with higher temperatures forum column stabilization help in the beggining?

Any comments on these observations above?