Metrohm 930 Compact IC Flex ChS/PP - Manual (Page 66)

5.4 Handling the eluent
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930 Compact IC Flex ChS/PP (2.930.1300)
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 have to be microfiltered (0.45 µm fil-
ter).
The composition of the eluent plays a critical role in chromatographic ana-
lysis:
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 (such as methanol, ace-
tone 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 has to be rinsed
with organic solvents, several solvents with rising or falling lipophilicity
must be used.
NOTE
To change the eluent, remove the separation column and connect the
capillaries using a coupling (6.2744.040) and two pressure screws
(6.2744.070).