Chromatography - What is a scouting gradient?

[CrimpJiggler]

I'm reading about gas chromatography at the moment and the notes I'm reading mentioned a "generic scouting gradient" but didn't explain what it is. I've been googling it and found a few HPLC tutorials (in GC its temperature gradient whereas in the HPLC tutorials they're talking about mobile phase composition gradient) which mentioned it but they don't explain what it is either. I'm aware that a "scouting gradient" is some kind of technique used to determine a good GC (or HPLC) method before performing the analysis but how does it work?

 

[turbo]

I think you are bumping up against a calibration technique that is designed to validate the accuracy of subsequent reading(s). I'm not sure about this because I only have experience with chromatography (mostly involving VERY stinky sulfurous compounds) in a pulp mill environment. Still, it was necessary to purge the column(s) and make calibration runs to be reasonably certain that the quantitative results were reasonable. Qualitative results were pretty well defined by arrival-times, but quantitative measures had to be calibrated more closely.

 

[Mike H]

In my experience, a scouting gradient is typically done in a manner where you're sharply varying a parameter in order to get an idea where to further develop the method. For example, you jump up from 50 mM salt to 1000 mM salt in order to elute your compound of interest. You can then estimate, based on a chromatogram of some sort, where your compound elutes and then do a more finely graded gradient to really nail it down. So if it appears to come off the column at 400 mM, you can zoom in with a less sharp gradient from 300 to 500 mM (or whatever you feel is appropriate).