VP-ITC MicroCalorimeter User’s Manual
is complete the tip of the injection syringe will be positioned to its original position, just
below the filling port. A beep will indicate the completion of the movement.
•
Click on the
Purge->ReFill
button again to repeat the purge/refill action.
The purpose of both purge/refill procedures is to dislodge any air bubbles from inside walls
of the injection syringe (which may have occurred during the first filling) and expel them
back into the titrant solution.
•
Carefully remove the pipette from its stand by picking it straight up till the glass barrel of the
injection syringe is above the top part of the pipette stand.
•
Carefully move the pipette so that it is directly above the center positioned sample cell access
tube (this is the hole on the right).
•
Carefully insert the pipette into the sample cell access tube.
Watch the end paddle of the long needle to insure it is inserted directly into the access hole,
hold the pipette vertical and slowly lower the pipette. When the pipette is almost completely
inserted you may have to push down slightly to compensate for the resistance of the rubber
o’ring to seat the pipette.
Precautions with Pipettes
Never assemble or disassemble the pipette/syringe assembly when the pipette screw is not in
it’s home (open port) position. Failure to raise the pipette screw prior to
assembling/disassembling the assembly will likely bend the pipette screw beyond repair.
The long needle and stir paddle on the pipette injection syringe must not be bent even
slightly
or baseline stability will be compromised. Exercise care at all times in the handling of
the pipette syringes. .
When removing the pipette from the instrument after an experiment ends ensure that the needle is
concentric with the access tube until the end of the stir paddle is clear of the hole. The syringe
should then be cleaned, dried, and stored safely.
The Pipette Stand is used to hold the pipette during filling, or merely for safekeeping. Users
should be aware that damage to the pipette injection syringe needles might be incurred when
placing them into the Pipette Stand. It is good practice pay close attention to the bottom tip of the
syringe needle paddle when inserting the injection syringes into the Pipette Stand. Do not place
the pipette assembly into it's stand until you are sure that there is clearance between bottom tip of
the syringe paddle and the filling tube.
The user should be aware that the design of the VP-ITC instrument is such that during an
experiment the syringe barrel is spinning (usually at ca. 310 RPM) while the plunger and Teflon
tip remain stationary. This causes the Teflon tip to wear away so eventually there will no longer
be a proper seal and the solution in the injection syringe may leak or not be properly injected.
The user should note the proper clearance between the plunger tip and glass syringe barrel and
replace the tip when the wear of the tip seems excessive.
When using the VP-ITC daily, we
recommend replacing the syringe tip once a month.
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