Metrohm 750 Autosampler - Manual (Page 45)

4 Notes – Maintenance – Faults
750 Autosampler
42
Fig. 11: Transfer needle replacement
4.2.3 Sample preparation
Experience has shown that most problems are caused by solids in the
sample solutions. Such particles can block the needle, transfer tubing
and the sample loop and also permanently damage the surfaces of the
injection valve seals. This is the reason why all samples must be filtered
before they are filled into the sample vials (procedure see chap. 4.1.2).
Solids may also be formed by the precipitation of buffer salts in the IC
system. With buffered samples it is recommended that the sample loop
feed is rinsed with a large volume of pure water after sample injection.
For example, this can be achieved by filling several (e.g. 5) sample vials
in sequence with distilled water after each sample and programming
them as rinsing samples without run time. This procedure also avoids
corrosion damage to the injection needle and the crystallization of salts.
17 17 Needle holder
55 Transfer needle
16 16 Ferrule
PEEK compression fitting 18 18
Nut 19 19
Connection screw 21 21
Centering sleeve 24 24
Clamping ring 22 22
Holder 23 23
Holder 20 20