5.4 Handling the eluent
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930 Compact IC Flex SeS (2.930.1400)
5.4.1
Manufacturing eluent
Chemicals used for manufacturing eluents must have a purity grade of at
least "p.a.". They may be diluted only by using ultrapure water (resistance
> 18.2 M
Ω
*cm). (These specifications apply generally for all reagents used
in ion chromatography.)
Newly manufactured eluents always need to be microfiltered (0.45 µm fil-
ter).
The composition of the eluent plays a critical role in chromatographic
analysis:
Concentration
An increase in the concentration generally leads
to shorter retention times and faster separation,
but also to a higher background conductivity sig-
nal.
pH
pH changes lead to shifts in dissociation equili-
bria and thus to changes in retention times.
Organic solvents
Adding organic solvents (e.g. methanol, acetone
or acetonitrile) to a watery eluent generally
speeds up lipophilic ions.
5.4.2
Changing the eluent
Ensure that no precipitates can form when changing the eluent. Immedi-
ately successive solutions must be miscible. If the system must be rinsed
with organic solvents, several solvents with rising or falling lipophilicity
must be used.
NOTE
To change the eluent, remove the guard column and the separation col-
umn. Connect the capillaries using a coupling (6.2744.040) and two
pressure screws (6.2744.070).
