IonPac CS14 Manual
Doc. No. 034848-10
Page 48 of 54
C.
Column contamination can lead to a loss of column capacity.
This is because all of the cation exchange sites will no
longer be available for the sample ions. For example, polyvalent cations from the sample or metals may concentrate on
the column. Refer to “Column Care,” for recommended column cleanup procedures.
Possible sources of column contamination are impurities in chemicals and in the deionized water used for eluents or
components of the sample matrix. Be especially careful to make sure that the recommended chemicals are used. The
deionized water should have a specific resistance of 18.2 megohm-cm.
D.
Diluting the eluent will improve peak resolution, but will also increase the analytes’ retention times.
If a 10%
dilution of the eluent is not sufficient to obtain the desired peak resolution, or if the resulting increase in retention
times is unacceptable, clean the column (see “Column Care”).
After cleaning the column, reinstall it in the system and let it equilibrate with eluent for about 30 minutes. No water
wash is necessary. 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
(see, “Dionex Worldwide Offices”)
6.6.3 Loss of Early Eluting Peak Resolution
Lack of equilibration to the initial eluent, improper system operation or improperly swept out void volumes are usually the
cause of poor resolution or efficiency of peaks eluting near the system void volume compared to the later eluting peaks.
A.
Be sure that the column is equilibrated to the initial eluent.
Typically gradient applications require approximately 10
minutes to equilibrate to the initial eluent. The minimum equilibration time can be determined by making successive
runs with increasing equilibration times. The column is equilibrated to the initial eluent when additional equilibration
time does not increase the runtime of the first eluting peaks.
B. 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.
C.
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.
6.7
Spurious Peaks
A.
Eluents made with chemicals lacking the required purity will contaminate columns rapidly.
Remake all stock
solutions and eluents using chemicals that meet the chemical requirements specified in Section 4.3, “Chemical Purity
Requirements.” Clean the column as indicated in “Column Care.”
B. Spurious peaks may be due to column contamination.
If the samples contain an appreciable level of polyvalent
cations, polyvalent cations may contaminate the column. As a result, the retention times for the analytes will
decrease, and spurious, inefficient peaks can show up at unexpected times. This problem may be solved by
increasing the time between analyses or by adding a regeneration step between successive runs to elute polyvalent
cationic contaminants off the column before the next sample injection takes place.
C.
An injection valve that needs service may produce baseline upsets.
This baseline upset can show up as one or
multiple peaks of varying size(s) and shape(s). Typically this will occur when the particular valve needs to be cleaned
or torqued (see the system manual). 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.
