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Why choose an Isolation Valve?
Maximum inertness
The use of high performance plastics and polymers such as PTFE, PEEK
and FFKM ensures that the liquid being handled by the valve is always
in a highly inert environment. There is no contact with any metallic
surfaces within the valve.
Fast response times
Switching time from port-to-port is generally less than 20ms across the
range of Isolation Valves.
Small footprint
Bio-Chem Fluidics Isolation Valves are specifically designed to be fitted
in tight spaces within instruments. The largest valve diameter is 1.25”
and longest overall length is less than 3”.
Minimal dead volume
Small overall size also helps keep the internal volumes minimized. The
valves are machined precisely to ensure that they have very low internal volumes (refer to specific product pages for details).
Applications
Precise, repeatable dispensing of reagents
Maintaining a repeatable dispense of aggressive (and often very expensive) reagents into an
analytical instrument can be problematic with conventional pumping equipment.
Some forward thinking instrument designers have abandoned the concept of using a pump
and have instead turned to using a Bio-Chem Fluidics Isolation Valve.
In such applications, a standard 2-way normally closed isolation valve is connected to a dip
tube, which is inserted into the bottom of a reagent bottle. Low pressure nitrogen (or other
appropriate inert gas) is introduced separately to blanket the volume above the liquid in the
reagent bottle. The pressure inside the bottle (maintained precisely at a calibrated low value) is
sufficient to force the reagent liquid up the dip tube.
Under “normal” conditions, the valve is not energized and remains closed so there is no flow.
When the valve is energized the diaphragm opens and flow through the valve is established.
The isolation valve now becomes a very repeatable fluid dispenser - the amount of liquid
dispensed is dependent only on the time the valve is open.
Aspirate and Dispense (“sip and spit”)
Sometimes the volume of liquid to be dispensed needs to be either a) very
small, b) extremely precise or c) both. In these situations it is very common to
use a precision machined syringe to control the dispense volume.
Bio-Chem Fluidics 3-way isolation valves are commonly used as the link
between the liquid reservoir, the syringe and the instrument. A 3-way valve
has three ports; normally open (NO in illustration), normally closed (NC) and
common (Com). The common port is connected to the syringe. When the
plunger is withdrawn, the valve is not energized and the flow is between the
reservoir and the syringe via the NO port (aspiration or “sip”).
When the syringe is pushed in, the valve is simultaneously energized. The flow
path switches to the NC port, which is connected to the instrument (dispense
or “spit”).
Although standard threaded port valves are common in this application, Bio-
Chem Fluidics can, as an option, supply valves with luer fittings to allow direct
coupling to the syringe (contact your regional sales office for more details).
Normally closed
Isolation valve
Custom
cap
Dispense
Reagent
bottle
Inert Gas
De-energized (”sip”)
Energized (”spit”)
NO
NC
Com
NO
NC
Com
F
l
o
w
p
a
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F
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Syringe
motion
Syringe
motion