IonPac NS1 Manual
Document No. 034024-06
Page 30 of 35
After cleaning the column, reinstall it in the system and let it equilibrate with eluent for about 30 minutes. The column
is equilibrated when consecutive injections of the standard give reproducible retention times. The original column
capacity should be restored by this treatment, since the contaminants should be eluted from the column. If you need
assistance in solving resolution problems, contact the nearest Dionex Office.
5.3.3 Loss of Front End Resolution
If poor resolutions and efficiencies are observed for the very early eluting peaks near the system void volume
compared to the later eluting peaks, check the following:
A. Improper eluent concentration may be the problem.
Remake the eluent as required for your application. Ensure that
the water and chemicals used are of the required purity.
B. Column overloading may be the problem.
Reduce the amount of sample ions being injected onto the analytical
column by either diluting the sample or injecting a smaller volume onto the column.
C. The column may not be equilibrated to the first eluent.
Increase the amount of time that the first eluent runs through
the columns before injection.
D. Sluggish operation of the injection valve may be the problem.
Check the air pressure and make sure there are no
gas leaks or partially plugged port faces. Refer to the valve manual for instructions.
E. Improperly swept out volumes anywhere in the system prior to the guard and analytical columns may be the
problem.
Swap components, one at a time, in the system prior to the analytical column and test for front-end resolution
after every system change.
5.4
Spurious Peaks
A. The column may be contaminated.
If the samples contain an appreciable level of polyvalent ions and the column is
used with a weak eluent system, polyvalent anions may contaminate the analytical column. The retention times for the
analytes will then decrease and spurious, inefficient (broad) peaks can show up at unexpected times. Clean the column
as indicated in “Appendix B - Column Care.”
B. If you need assistance in determining the best way to clean strongly retained solutes in your specific sample matrix from
the IonPac NS1 columns, contact the nearest Dionex Office.
C. The injection valve may be creating a baseline disturbance.
This baseline upset can show up as a peak of varying
size and shape. It will happen when the injection valve needs to be cleaned or retorqued (see valve manual). Check to
see that there are no restrictions in the tubing connected to the valve. Also check the valve port faces for blockage and
replace them if necessary. Refer to the Valve Manual for troubleshooting and service procedures. Small baseline
disturbances at the beginning or at the end of the chromatogram can be overlooked as long as they do not interfere with
the quantification of the peaks of interest.
If cleaning and retorquing the valve does not help, replace the valve. Use a Dionex High Pressure Injection Valve (P/
N 037142) or a Dionex High Pressure Inert Valve (P/N 037143) as required.
For DX-300 systems equipped with a Rheodyne Microinjection Valve, Model 9126 (Dionex P/N 044697), consult the
accompanying manual for service instructions. See Section 2.2, “The Injection Loop,” for injection valve and loop
requirements for 4-mm operation.
