IonPac CS14 Manual
Doc. No. 034848-10
Page 47 of 54
2.
Dips on either side of an analyte peak's base.
Non-linear response or loss of sensitivity may occur when the suppressor is contaminated with carbonate. This
contamination is possibly from dissolved carbon dioxide in the DI water. Degassing will help minimize the presence
of carbon dioxide in acidic eluents or in DI water. Note, when pressurizing eluent reservoirs on the system use inert
gases such as nitrogen (aqueous applications) or helium (aqueous or solvent applications).
When the CSRS suppressor is contaminated with carbonate the following treatment is recommended.
1.
Push 5 mL of 2 M NaOH (freshly prepared) through the
ELUENT IN
port and divert a line from the
ELUENT OUT
port to waste.
2.
Push 10 mL of 2 M NaOH (freshly prepared) through the
REGEN IN
port and divert a line out from the
REGEN
OUT
port to waste.
3.
Allow the suppressor to equilibrate for 20 minutes.
4.
Repeat steps 1 and 2 with degassed DI water and reinstall the unit on the system.
5.
If problem persists repeat steps 1–4.
6.6
Poor Peak Resolution
Poor peak resolution can be due any or all of the following factors.
6.6.1 Loss of Peak Efficiency throughout the Chromatogram
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 submitting it to high pressures. Remove the column’s top end fitting (see Section 6.1.2,
“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.
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 i.d. of no greater than 0.010" for 4-mm systems or no greater than 0.005" for 2-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.
C.
Check the sample for column overloading.
Overloading the column and/or injecting samples in very acidic matrices
(>50 mM H
+
) can cause poor efficiencies.
6.6.2 Loss of Resolution Throughout the Chromatogram 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 flow rate.
See if the eluent flow rate is equivalent to the flow rate specified by the analytical protocol.
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.
An eluent that is too concentrated will
cause the peaks to elute faster. Prepare fresh eluent. If you are using a gradient pump to proportion the eluent,
components from two or three different eluent reservoirs, the resulting eluent composition 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%.
