Stationary phase, Sample solution – Metrohm 791 VA Detector User Manual

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3.1 Electrochemical detection

791 VA Detector

sulfuric acid, perchloric acid, lithium perchlorate, etc. can be used for

this. Chlorides and hydroxycarboxylic acids should not be used; some

reagents which form ion pairs can be used.
Solvent gradients can be used in less sensitive ranges (current range >

100 nA). The eluent is degassed as usual by vacuum or passing a

stream of helium through it.

Stationary phase

In principle all reversed-phase and ion exchanger materials can be

used. New columns must be purged well and for a sufficiently long time

for any contaminants which may be present to be washed out. This

"equlibration phase" of a column may take more than 24 hours in the

most sensitive areas.

Sample solution

Whenever possible, the eluent used should also be used as the solvent

for the sample in order to minimize interference owing to changing sur-

roundings (as small a front peak as possible). Very small amounts of

the active substance should be used, in general < 100 ng.