Waters ACQUITY UPLC M-Class - Page 70

4.3.2.9 Fronting peaks
Suspected cause Possible solution
Injection volume or sample concentration is too
high, disrupting column equilibrium.
Reduce the injection volume or dilute the
sample.
Sample diluent is too high in organic for the
initial mobile phase.
Reduce the injection volume or reduce the
percentage of organic.
Needle weak wash solvent is too high in the
organic sample.
Ensure that the weak needle wash solution is
similar to the initial mobile phase.
Note: The volume of weak needle wash
should be three times strong wash volume.
Column or pre-column is contaminated. Clean the column or pre-column or replace.
See also: The appropriate column care and
use guide on the documentation CD.
Column degraded forms a void. Verify column performance. If efficiency is low,
replace it.
Trap column is degraded. • Remove the trap column and perform a
direct injection.
• If results are normal, replace the column
and perform a set pressure diagnostic.
4.3.2.10 Missing peaks
Suspected cause Possible solution
Wrong sample injected Check or replace the sample.
Degraded or contaminated sample or standard • Inject a known good standard.
• If the fewer peaks problem persists, use
fresh mobile phase and flush the system.
• If fewer peaks persist, clean or replace the
column.
Loss of resolution • Check the fluidic connections for dead
volumes.
• Change your column.
• Verify if It is time to service the mass
spectrometer.
• Confirm the vial location.
November 26, 2019, 715003588 Revision C
Page 70