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Calibration curve slope

Posted: Mon Apr 03, 2006 2:57 pm
by zimanli
I did 3 calibration curves on 3 different days, and I had some problems with them:
1. the slope is increasing.
2. the absolute response for the same solution increases.

Is this due to solvent evaporation from my standard solution or from the contamination of my system?

Thanks a lot!

answer

Posted: Mon Apr 03, 2006 3:44 pm
by chromatographer1
Could be either one or both,

OR

it could be another reason based on sample introduction or detector response.

Ain't analytical chemistry fun?

best wishes,

Rod

Posted: Mon Apr 03, 2006 7:07 pm
by zimanli
Thanks for your reply!

I found that I used split injection on one day and splitless injection on the other 2 days.

Posted: Tue Apr 04, 2006 2:31 am
by KC
shoot some acetone blanks and if you get a peak at the retention of your analyte you may well have coated your inlet with your test substance and it bleeds off with each injection. Is an acetone blank clean? What do 3 or 4 injections of acetone in succession look like. If it is tapering off raise injector temp 30 C and shoot another. If it gets bigger then I would definately guess that is the problem

Posted: Tue Apr 04, 2006 2:20 pm
by zimanli
I would try what KC suggested. It is a good way to rule out contamination. Thanks

aetone blanks

Posted: Tue Apr 04, 2006 2:58 pm
by Peter Apps
KC has been recommending acetone blanks. Before you follow that advice have a look at the thread on "Peak tailing - chlorinated aromatics with phenol and aldehydes" started by khirth.

Peter