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Accessories
Flow-Thru Cap
A flow-thru cap (Orion No. 950025) is available for converting the
carbon dioxide electrode to a flow-thru electrode, especially useful for
measuring small samples anaerobically. The electrode is assembled
using the flow-thru cap in place of the bottom cap supplied with the
Orion 95-02 electrode (see
Figure 7
). When the electrode is placed in
the electrode holder, it should be tilted at a 20° angle with respect to
the support rod. The outlet of the flow-thru cap should be furthest
from the support rod. The inlet of the cap is 18-gauge (small bore),
stainless steel tubing and the outer is 14-gauge (large bore), stainless
steel tubing.
The sample is introduced into the measuring chamber by a syringe
pump or peristaltic pump. Recommended pumps include the Sage
Orion 351 Syringe Pump and Orion 375A Peristaltic Pump
(manufactured by the Sage Instruments division of Orion) The
volume of the measuring chamber is about 0.1 mL. To remove all
traces of the previous sample, 0.5 to 1 mL of sample must be passed
through the electrode. A flow rate of 2 mL per minute is
recommended.
If a peristaltic pump is used, continuous measurements can be made
by pumping sample solution and carbon dioxide buffer in different
channels, mixing the two streams and flowing the mixed stream
through the electrode.
red O-ring
flow-thru cap
small inlet
membrane-spacer
assembly
large outlet
Figure 7
Electrode Assembly With Flow-Thru Cap