Metrohm 930 Compact IC Flex Oven/SeS/PP - Manual (Page 71)

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5 Operation and maintenance
930 Compact IC Flex Oven/SeS/PP (2.930.2500)
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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.
5.5.2 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).
5.6 Notes on operating the high-pressure pump
CAUTION
The pump head is filled ex works with methanol/ultrapure water. Ensure
that the eluent used is miscible with this solvent.
Keep the following recommendations in mind in order to protect the
high-pressure pump from damage as much as possible during operation:
￭ To protect the high-pressure pump from foreign particles, we rec-
ommend filtering the eluent through a filter with a pore size of 0.45
µm and aspirating it via an aspiration filter (6.2821.090).