7.
Missing peaks
There are four
possible reasons why an expected peak may be missing:
1. It was never
there in the first place. Check that your standard was correctly
made up, and then re-run the standard.
2. It is there,
but you can't see it. Check the detector wavelength setting and
sensitivity.
3. It was there,
but now has gone. Make up a fresh standard and re-run.
4. It has moved. Check
to see if any "new" peaks have appeared; if none are found, check to
see if any of the other peaks have increased in area. If so, the
problem is due to a change in the selectivity of your system. In this
case, you should consider the following steps:
A. Check
that the column temperature is correct (if the column
compartment temperature setting is correct, use a thermometer to
confirm the actual temperature).
B. Check to confirm
that the mobile phase was correctly prepared (especially if the problem
coincided with a new batch of mobile phase!).
C. Check to make
sure that the correct type of column is being used.
D. If the column is
nearing the end of its useful lifetime, replace the column.
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LC Resources, Inc. all rights reserved