Teledyne ACCQPrep HP125 Installation And Operation Manual page 63

· Semivolatile compounds may be difficult to detect or
may benefit from modification of the ELSD sensi-
tivity, gain or operating temperatures. Refer to the
discussion on ELSD operation in section 5.2.7 before
adjusting the ELSD operating temperatures.
· Check P-trap (see discussion on "No Peaks Detected".
• UV and ELSD signals aren't aligned in time
· The peak widths or shapes of the 2 signals may vary
due to varying sensitivity of the 2 detectors causing
the alignment to appear incorrect.
· If the signals sometimes appear a few seconds out of
alignment it could be normal due to different peak
shapes common with ELSD.
· Partial blockage of the ELSD .005" red split tubing
could reduce flow to the ELSD causing the ELSD
signal to lag the UV signal.
• UV or ELSD peaks are broader than the other detector.
· This is normal due the detector response and a small
increase in dispersion in the alignment compensation
tubing.
PurIon detection problems –
• Little or no mass spectrum detected on method devel-
opment screen, but compound should be visible.
· Sample is dissolved in a solvent not suitable for MS
injection such as DMSO or DMF. Dissolve in
methanol or acetonitrile and try again.
· Try other ionization parameters, such as switching to
"Robust".
· Verify that the gas supply is functioning. Small peaks
may be visible without the gas. Nitrogen is typically
used.
· Make sure the proper gas is supplied. Argon will
cause arcing resulting in noise.
· Fluid interface carrier solvent bottle empty.
• MS peaks occur later than peaks from the other detector
such as UV.
The MS carrier fluid flow rate is too low. Check that the fluid
interface priming port is fully closed. Check the carrier pump
seals for leakage. Clean or replace the carrier pump check valves.
Excessive system pressure –
• If using a Column Select Valve Module (CSVM) make
sure the column is connected properly (if the column
output goes to the wrong port, it is dead-ended).
• Column getting clogged:
ACCQPrep HP125
Section 4 Operation
4-17