5
–
Troubleshooting
Thermo Scientific
Product Manual for IonPac AS31 Columns
Page 30 of 45
155007-01
For Research Use Only. Not for use in diagnostic procedures.
Retention Time Drift
Contaminated sample or
eluent, Poorly mixed eluent
Remake Sample/Eluents
Temperature variability
Use a thermostatted oven,
check oven operation
, Component
Manual
Poor pump priming or loss of
prime
Prime Pump
, Component
Manual
Inconsistent flow due to
leaking pump
Repair pump
,Component Manual
Oscillating Retention
Time
Pump Problems
Recalibrate/Repair Pump
Component Manual
Temperature variability
Use a thermostatted oven,
check oven operation
, Component Manual
Sluggish Injection valve
Service Valve
, Component Manual
Poor Front End
Resolution
Conc. Incorrect Eluents
Remake Eluents
Column Overloading
Reduce Sample Size
Large System Void Volumes
Replumb System
Component Manual,
Spurious Peaks
Sample Contaminated
Pretreat Samples
Sluggish Injection Valve
Service Valve
, Component Manual
Analyte Specific
Efficiency Loss
Column Contamination from
sample or system
Purge contamination, employ a
trap or guard column, clean or
replace column
5.1
High Back Pressure
5.1.1
Finding the Source of High System Pressure
Total system pressure for the Dionex IonPac AG31 Guard Column plus the Dionex IonPac AS31
Analytical Column when using the test chromatogram conditions should be less than 3800 psi. If
the system pressure at the standard flow rate is higher than the maximum operational pressure for
the system, it is advisable to determine the cause of the high system pressure.
A.
Make sure that the pump is set to the correct eluent flow rate. Higher than recommended
eluent flow rates will cause higher pressure. Measure the pump flow rate if necessary with a
stopwatch and graduated cylinder to confirm flow rate is correct. Pre-weigh the graduated
cylinder and calculate the weight of eluent collected to obtain a more accurate measure of
flow.
B.
Determine which part of the system is causing the high pressure. High pressure could be due
to plugged tubing or tubing with collapsed walls, an injection valve with a clogged port, a
guard or separator column with particulates clogging the bed support, a clogged High-
Pressure In-Line Filter, the suppressor, or the detector cell.
C.
To determine which part of the chromatographic system is causing the problem, disconnect
the pump eluent line from the injection valve and turn the pump on. Watch the pressure; it
should be at its lowest (< 50 psi) with everything disconnected. The pressure with the eluent
generator connected should be < 200 psi. Continue adding system components (injection
valve, column(s), suppressor, and detector) one by one, while monitoring the system pressure.
The pressure should increase up to a maximum when the Guard and Analytical columns are
connected.
D.
Measure the system back pressure by attaching a short piece of new 0.010” tubing in place
of the column.