Metrohm 881 Compact IC pro – Cation - Manual (Page 24)

3.5 Capillary connections in the IC system
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881 Compact IC pro – Cation
￭ PEEK capillaries (6.1831.030) with an internal diameter of 0.75 mm for
sample handling in the ultra trace range.
Caution
For the capillary connections between the injection valve and detector ,
PEEK capillaries with an internal diameter of 0.25 mm must be used.
These are already connected to a newly delivered instrument.
PTFE capillaries (poly-
tetrafluoroethylene) PTFE capillaries are transparent and enable visual tracing of the liquids to
be pumped. They are chemically inert, flexible and temperature-resistant
up to 80°C.
Usage:
PTFE capillaries (6.1803.0x0) are used for the low pressure range.
￭ PTFE capillaries with internal diameter of 0.5 mm for sample handling.
￭ PTFE capillaries with internal diameter of 0.97 mm for sample handling
as well as for rinsing solutions (they do not have to be in the scope of
delivery of the instrument).
Capillary connections
In order to achieve optimum analysis results, capillary connections in an IC
system must be absolutely tight and free of dead volume. Dead volume
occurs if two capillary ends connected to each other do not fit exactly,
thus allowing liquid to escape. There are two possible reasons for this:
￭ The capillaries do not have exactly cut edges.
￭ The two capillary ends do not completely meet.
One prerequisite for dead volume free capillary connection is, that both
capillary ends are cut exactly plane. Therefore we recommend only to cut
PEEK capillaries with the capillary cutter (6.2621.080).
Creating dead volume free capillary connections
To create dead volume free capillary connections, proceed as follows:
1 Slide the pressure screw over the capillary. Ensure that the capillary
protrudes 1–2 mm from the tip of the pressure screw.
2 Plug the capillary all the way into the connection or coupling until
the stop.
3 Only then start turning the pressure screw, while keeping the capil-
lary pressed in space.