Metrohm 850 Professional IC Anion MSM-HC - LP-Gradient - Manual (Page 79)

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5 Operation and maintenance
850 Professional IC Anion MSM-HC LP Gradient
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5.4 Eluent
5.4.1 Production
The chemicals used for the production of eluents should have a degree of
purity of at least "p.a.". Only ultra pure water (resistance > 18.2 M
Ω *cm)
may be used for dilution (this generally applies for reagents which are
used in ion chromatography).
Newly produced eluents should always be microfiltered (filter 0.45 µm).
Caution
Only microfiltered (filter 0.45 µm) eluents may be used.
The composition of the eluent has a crucial effect on the chromatographic
analysis:
Concentration An increase in the concentration generally leads
to shorter retention times and faster separation,
but also to higher background conductivity.
pH pH changes result in shifts in the dissociation
equilibria and hence changes in the retention
times.
Organic solvents The addition of an organic solvent (e.g. metha-
nol, acetone, acetonitrile) to aqueous eluents
generally accelerates lipophilic ions.
5.4.2 Operation
5.4.2.1 Supply bottle
The supply bottle with the eluent must be connected as indicated in chap-
ter 3.9.1, page 29. This is above all important for eluents with volatile sol-
vents (e.g. acetone).
Moreover, condensation must also be prevented in the eluent bottle. Drop
formation can change the concentration ratio in the eluent.
5.4.2.2 Aspiration filter
To protect the IC system against foreign particles, we recommend aspirat-
ing the eluents via a 6.2821.090 aspiration filter (12-2). This aspiration fil-
ter must be replaced should it show signs of yellow discoloration (but no
later than every 3 months).
In the case of very sensitive measurements, the eluent should be stirred
constantly with a magnetic stirrer.