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IonPac AS3, AS4, AS5, CS2
one of the proportioned eluents is less than 5%.
C. Column contamination can lead to a loss of column capacity. This is because all of the ion exchange sites will no longer
be available for the sample ions. Polyvalent anions might be concentrating on the column. Refer to Section 6.3, "Column
Cleanup," for recommended column cleanup procedures.
Possible sources of column contamination are impurities in chemicals and in the deionized water being used. Be especially
careful to make sure that the recommended chemicals are used. The deionized water should have a specific resistance
of at least 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 Section 6.3, "Column Cleanup").
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 (see, "DIONEX Worldwide Offices").
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. 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.
D. 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 columns 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 Section 6.3, "Column Cleanup".
If you need assistance in determining the best way to clean strongly retained solutes in your specific sample matrix off
of DIONEX columns, contact the nearest DIONEX Office (see, "DIONEX Worldwide Offices").
B. The injection valve may need maintenance. When an injection valve is actuated, the possibility of creating a baseline
disturbance exists. 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. Consult the nearest DIONEX Office (see, "DIONEX
Worldwide Offices") for help in services or replacing a suspect valve.
Document No. 032226-14
Page 14 of 14
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