Chromatography Forum

I would like to know how common is to inject pure solvent (DCM, methanol, etc.) between sample (such as bio-oil, diesel) injections.

Some students (like those in my university) make a single solvent injection between every sample, but other operators says there's no need for that - a few minutes (5-10) near the maximum column temperature is enough for cleaning out any 'impurities' present in the column.

Any ideas?

I would guess that someone has been overflashing the injection liner and depositing residues in the pneumatics. Thus by injecting another slug of solvent they tend to wash out these residues so that don't interfere with the next sample.

If injections are done properly, there is no reason to inject a blank solvent between samples, unless you want to know your liner is dirty and absorbing residues or your injector system has been compromised.

My guess is things are not as 'pure as snow', thus the need for extra 'washings'.

best wishes,

Rod