Teledyne ACCQPrep HP125 Installation And Operation Manual page 62

ACCQPrep HP125
Section 4 Operation
4-16
• Impurities in solvent; evaluate with runs with no
sample injection to determine if impurity is from the
sample. Make a run with a standard injection volume,
then double the equilibration time. If the peak in
question become larger, it is solvent related. Check
mobile phase quality, check for fungal/bacterial growth,
or ignore the peak.
Drifting baselines –
• Mobile phase absorbance which may be due to an
impurity in the solvent or a solvent modifier.
• Column not equilibrated; increase the equilibration time
to determine if this solves the problem.
• A compound from a previous run was not fully washed
from the column and is slowing coming out of the
column. Wash the column with strong solvent to
eliminate compounds from prior separations.
ELSD detection issues –
• No peaks detected
· If the compounds are volatile, they may not be
detected by ELSD or may need a lower drift tube
temperature. Refer to the discussion on ELSD
operation in section 5.2.7 before adjusting the ELSD
operating temperatures.
· If the system detects peak shortly after the first
separation of the day and then fails to detect, the
drift tube temperature may be too low to vaporize the
solvent aerosol or the spray chamber too warm to
condense out excess higher boiling point solvents.
Refer to the discussion on ELSD operation in section
5.2.7 before adjusting the ELSD operating tempera-
tures.
· Verify P-trap contains fluid. If using reverse phase
solvents with recommended conditions there should
be a small amount of fluid draining from the P-trap.
Fill the P-trap if needed (see section 2.2.4)
· Increase ELSD sensitivity and gain in the method
editor to see if the peaks are simply too small to be
easily seen.
· Flow splitter tube blocked. This .005" ID red colored
tubing may be plugged by sample. Remove the tubing
from the nebulizer during operation to verify flow
through the tubing. If plugged replace both segments
of tubing.
• Weak UV or ELSD peaks
· Each detector has a different response to compounds
and may be more or less sensitive to compounds than
the other detector.