Metrohm 789 Robotic Sample Processor XL - Manual (Page 49)

2.4 Connecting up accessories
Metrohm Sample Processor, Installation 41
Aspiration tip
In the macro titration head the M8 aspiration tip (6.1543.170) is placed
in a vertical opening (SGJ9). In the micro titration head a vertical open-
ing is also used. The tip is connected with a piece of PTFE tubing
(6.1805.510) and a 6.1820.030 Screw connector to Pump 2 (marking on
valve ' ').
Rinsing process
In an ideal rinsing process (with two pumps) the sample solution is first
aspirated off. The electrode is then rinsed in an empty beaker and the
rinsing solution is aspirated off at the same time. A short overrun of the
aspiration pump ensures that the sample vessel (or titration cell) is
emptied completely.
Sequence:
PUMP 1.2 : 10 s
PUMP 1.* : 3 s
PUMP 1.2 : 3 s
Chemical resistance
The pump heads of the membrane pumps, the connection nipples and
the union nuts are made of PVDF. PVDF is resistant to many chemicals.
The following should not be used: acetone, acetic anhydride or di-
methylformamide (DMF). The membrane, the valve disks and valve
components are made of PTFE and are resistant to almost all chemi-
cals.
If your sample contains solids (e.g. silver chloride) or sticky substances
then, instead of the membrane pump built into the Sample Processor,
you should use the 772 Pump Unit.
The polyethylene canisters (6.1621.000) used as rinsing or waste canis-
ters are (only) suitable for aqueous solutions.
2.4.2 Attaching the tubing
Fig. 18 Attaching the tubing
For attaching the tubing the individual
chain links can be opened with a
screwdriver or similar object.
Mind the markings on the chain links.