5
– Troubleshooting Guide
Thermo Scientific
Product Manual for CarboPac PA200 Columns
Page 29 of 37
065734-01
For Research Use Only. Not for use in diagnostic procedures.
5.2.2
A Contaminated Guard or Analytical Column
A.
Remove the columns from the system.
B.
Install a back pressure coil that generates approximately 2000 psi and continue to pump
eluent. If the background decreases, the column(s) is (are) the cause of the high
background.
C.
To eliminate downtime, clean or replace the analytical column at the first sign of column
performance degradation. Clean the column as instructed in, “
Appendix A, Dionex
CarboPac PA200 Column Care”.
5.3
Poor Resolution
One of the unique features of Dionex CarboPac columns is the fast equilibration time in gradient
applications from the last eluent (high ionic strength) to the first eluent (low ionic strength). The
actual equilibration time depends on the ratio of the strongest eluent concentration to the weakest
eluent concentration and application flow rate. Typically equilibration times range from 15 to 20
minutes for both 1-mm and 0.4-mm columns.
If increased separation is needed for early eluting peaks, reduce the initial eluent concentration.
Due to different system configurations, the gradient profile may not match the gradient shown in
example applications in the product column manual. Gradient conditions can be adjusted to
improve resolution or to adjust retention times either by changing the gradient timing or by
changing the initial and/or final eluent concentration.
A.
Keep the eluent concentrations constant and adjust the gradient time. This is the simplest
way to compensate for total system differences if resolution is the problem.
B.
Change the initial and/or final eluent concentration and adjust the gradient time. This
approach requires more time to develop and more knowledge in methods development
work. Its advantage is that it allows a method to be tailored for a particular application,
where selectivity, resolution, and total run time are optimized. Be aware poor peak
resolution can be due to any or all of the following factors.
5.3.1
Loss of Column Efficiency
A.
Check to see if headspace has developed in the guard or analytical column. This is
usually due to improper use of the column such as exposing it to high pressures. Remove
the column’s inlet end fitting (see Section 5.1.2, “Replacing Column Bed Support
Assemblies”). If the resin does not fill the column body all the way to the top, the column
must be replaced.
B.
Extra-column effects can result in sample band dispersion, making the peaks’ elution
less efficient. Make sure you are using PEEK tubing with an ID of no greater than
0.0025" for both 1 mm and 0.4 mm systems to make all eluent liquid line connections
between the injection valve and the detector cell inlet. Cut the tubing lengths as short as
possible. Check for leaks. For capillary systems, only use precut tubing of the same type.
C.
If tubing is not connected properly from the inlet and outlet of the column, it can cause
low efficiency. When installing Dionex CarboPac columns, it is recommended to turn
off the pump while connecting the column inlet and the column outlet to the detector.
This will avoid any slippage of the ferrule under high pressure conditions which can
cause low peak efficiencies.
