IonPac NS1 Manual
Document No. 034024-06
Page 29 of 35
2. Test the Anion AutoRegen Regenerant Cartridge to see if it is expended.
If the background conductivity is low
when freshly prepared regenerant is run through the ASRS or CSRS without an AutoRegen Accessory in-line then
the cartridge is expended. Connect a freshly prepared regenerant to the Anion AutoRegen Regenerant Cartridge.
Pump approximately 200 mL of regenerant through the Anion AutoRegen Regenerant Cartridge to waste before
recycling the regenerant back to the regenerant reservoir.
If the background conductivity is high after placing the AutoRegen Accessory in-line, you probably need to replace
the Anion AutoRegen Regenerant Cartridge (P/N 039564). Refer to the “AutoRegen Regenerant Cartridge Refill
Product Manual” (Document No. 032852) for assistance.
5.3
Poor Peak Resolution
Poor peak resolution can be due any or all of the following factors.
5.3.1 Loss of Column Efficiency
A. Ensure that system void volumes have been minimized.
Extra-column system effects can result in sample band
dispersion and decreasing peak efficiencies. Make sure you are using PEEK tubing with an i.d. of no greater than 0.010"
to make all eluent liquid line connections between the injection valve and the detector cell inlet on 4-mm systems. Make
all tubing lengths are as short as possible. Check for leaks.
B. Check to see if headspace has developed in the guard or analytical column
(e.g., due to improper use of the column
such as submitting it to high pressures). Remove the column’s top 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, it means that the resin bed
has collapsed, creating a headspace. The column must be replaced.
5.3.2 Poor Resolution Due to Shortened Retention Times
Even with adequate system and column efficiency, resolution of peaks will be compromised if analytes elute too fast.
A. Check the eluent flow rate.
If it is different than the flow rate specified by the analytical protocol, recalibrate the pump.
Measure the eluent flow rate after the column using a stopwatch and graduated cylinder.
B. Check to see if the eluent compositions and concentrations are correct.
For isocratic analysis,
an eluent that is too strong will cause the peaks to elute faster. Prepare fresh eluent. If you are
using a gradient pump to proportion the final eluent from concentrated eluents in two or three different eluent reservoirs,
the composition of the final eluent may not be accurate enough for the application. Use one reservoir containing the
correct eluent composition to see if this is the problem. This may be a problem when one of the proportioned eluents
is less than 5%.
For gradient analysis,
remake the eluents or adjust the times in the gradient program to obtain the required peak
resolutions.
C. Column contamination can lead to a loss of column capacity
because fewer of the anion exchange sites will be
available for the sample ions. Polyvalent anions or metal ions might be concentrating on the column. Refer to Appendix
B - Column Care, for recommended column cleanup procedures.
Possible sources of column contamination are impurities in chemicals, in the deionized water or from the sample matrix
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 (“Appendix B - Column Care”).
