GE Analytical Instruments ©2006 13-5 DLM 14291 Rev. A
• Open the outlet stopcock on the purge vessel and on the gas bubbler.
• Adjust the gas flow into the purge vessel using the needle valve so that the
cell pressure with the purge vessel connected is the same as recorded when
the frit restrictor was open to the atmosphere (typically 4-7 torr).
The vanadium reagent should turn from blue to green when the water bath
reaches 80-90 °C. If the reagent does not change color, the vanadium has been
oxidized and fresh reagent should be prepared.
The background signal on the NOA will usually go offscale on the high
sensitivity setting when fresh VCl
3
/HCl reagent is purged. The background will
drop with continued purging, with a final baseline of 10-50 mV.
Leak Check for Purge Vessel
The best way to ensure that all of the connections to the purge vessel and gas
bubbler are tight is to see if the VCl
3
/HCl reagent will vacuum distill when the
gas flow is turned off. The water bath should be at 95 °C for this test. To
perform the leak check:
• Close the needle valve on the purge vessel to stop the flow of gas.
• After a few seconds, the VCl
3
/HCl reagent should begin to vacuum distill as
indicated by the violent boiling with large bubbles.
• If the reagent does vacuum distill, all of the connection are tight. Open the
needle valve and adjust the gas flow rate to match the cell pressure
determined above.
• If the reagent does not vacuum distill, there is a leak that must be fixed.
The most common location is the Teflon sleeve in the gas bubbler. Make
sure the top and bottom connections are tight. Other sources include the
Swagelok connections (make sure the ferrules are in place and the
connections are tight) and the connections at the IFD filter.
Adjustment of Liquid Level
To Next Page
Loading...
Need help?
General
