4
–
Example Applications
Thermo Scientific
Product Manual for IonPac AS31 Columns
Page 18 of 45
155007-01
For Research Use Only. Not for use in diagnostic procedures.
4.
Example Applications
4.1
Recommendations for Optimum System Performance
The chromatograms in this section were obtained using columns that reproduced section 4.2 (
Isocratic Elution With
and Without a Guard Column
) on optimized Ion Chromatographs. Different systems will differ slightly in performance
due to slight differences in column sets, system void volumes, liquid sweep-out times of different components, and
laboratory temperatures.
The Dionex IonPac AS31 is designed for the determination of haloacetic acids using a hydroxide gradient eluent
delivered by an Eluent Generator. In any type of gradient elution system, it is important to use eluents that produce a
minimum shift in baseline conductivity during the run as well as a fast equilibration time from one run to the next. The
best choice for an eluent is potassium hydroxide as it is converted to water in the suppressor. As long as the capacity
of the suppressor is not exceeded, the eluent hydroxide concentration has little effect on background conductivity. For
example, a gradient run can begin at 17 mM KOH and end at 85 mM KOH, with a resulting total baseline change of 1
to 2 µS.
Ensure that adequate equilibration time is allowed between runs. If a downward shift in the baseline is observed during
the isocratic section of the chromatogram, increase the equilibration time.
You can increase the sensitivity of your system by using sample concentration techniques. However, none have been
used for the test chromatograms.
Carbon dioxide readily dissolves in dilute basic solutions forming carbonate. Carbonate contamination of eluents can
affect the retention times of the anions being analyzed. Eluents should be maintained under an inert helium atmosphere
to avoid carbonate contamination.
