Manual

4 Notes – Maintenance – Faults
750 Autosampler
40
A further possible way of filtering samples is by means of the optional
6.2743.030 filter stoppers. These filter stoppers, which contain a
built-in filter unit, are fitted to the sample vials just like normal stoppers.
The way they work is shown in Fig. 10.
Fig. 10: Sample filtering with FilterCaps
FilterCaps were designed to free the chromatographer from the time-
consuming task of hand filtering samples. They can be used to free
samples from suspensions and particles. However, filter stoppers are
not suitable for filtering samples containing a large amount of solids as
this causes the filter to become blocked which also blocks the transfer
needle. Those samples which are difficult to filter manually with a mem-
brane filter (see Fig. 9) should be centrifuged before filtration.
When working with filter stoppers the "POS4" setting for the needle
immersion depth "Needle Depth" must not be selected.
4.1.3 Operating parameters
Before samples can be injected all necessary instrument settings must
be made. The most important parameter is the retention time. The time
interval "Run Time" between individual injections must be sufficiently
long so that all substances are eluted before the next sample is in-
jected. Moreover, it may be necessary to include further time for base-
line analysis and evaluation with the evaluation system.
Filtered sample
Unfiltered sample
To injection valve