Metrohm 861 Advanced Compact IC - Manual (Page 78)

4 Notes - Maintenance - Faults
861 Advanced Compact IC / Instructions for Use 8.861.1033
68
low buffering capacity one should preferably use a CO
2
absorber (see
Section 2.6.3).
The supply vessel containing the eluent must be closed as tightly as
possible to avoid excessive evaporation. This is primarily important with
eluents containing organic solvents (e.g. acetone), the evaporation of
which can lead to drifts in the long term. If work is performed in a very
sensitive range, even if one drop of condensate falls back in the eluent
this can cause a noticeable change in the background conductivity.
Influence of various parameters on anion columns
• Concentration: An increase in the concentration usually leads
to shorter retention times and quicker separa-
tion, but also to a higher background conduc-
tivity.
• pH: pH alterations lead to shifts in the dissociation
equilibrium and thus to changes in the reten-
tion times.
• Organic modifiers: Addition of an organic solvent (e.g. methanol,
acetone, acetonitrile) to aqueous eluents
generally accelerates lipophilic ions.
Eluent change
When changing the eluent you must make sure that no precipitation
can occur. This means that solutions used in sequence must be misci-
ble. If the system needs to be rinsed with organic solvents then it may
be necessary to use several solvents with increasing or decreasing
lipophilicity (e.g. water ↔ acetone ↔ chloroform).
4.1.4 Peristaltic pump
The pump tubings used by the peristaltic pump are consumable mate-
rial with a limited lifetime and should be exchanged at regular intervals
(approx. every 4 weeks under continuous use; see Section 4.2.10).
The working life of pump tubing depends to a considerable extent on
the contact pressure. This is why the contact pressure must be cor-
rectly set as described in Section 2.10.2. If the pump is to remain
switched off for a lengthy period of time the tubing cartridges 47 should
be raised completely by loosening the snap-action lever 50 on the right-
hand side (the set contact pressure remains unchanged).
4.1.5 Suppressor module «MSM II»
Protection
To avoid contamination of the suppressor module «MSM II» by foreign
particles or bacterial growth, a filter 6.2821.130 58 (part of the "PEEK
Coupling 81 with filter and tubing security device" 6.2744.180 ) must be
installed between peristaltic pump and inlet capillaries of the suppres-
sor module «MSM II» (see Section 2.8.2).