GE Analytical Instruments ©2006 12-13 DLM 14291 Rev. A
All cell culture media, the buffers used for perfusates or organ baths, will contain
some nitrite. This background contamination will determine the minimum
concentration of nitrite that can be measured in the samples. If a commercial
media is used, talk to the supplier about purchasing media low in nitrite. If
preparing the media or buffers, check the chemicals used in the preparation for
nitrite contamination. In some cases, the nitrite contamination is introduced
during filtration or storage of the media. Rinsing all equipment, filter paper, etc.
with nitrite-free, deionized water prior to use will help minimize contamination.
Replacing the Reducing Agent and Opening the Purge Vessel
Under normal operating conditions, the purge vessel is under a slight vacuum. In
order to open the purge vessel or drain the reducing agent from the vessel, it is
necessary to bring the pressure in the purge vessel back to near atmospheric
pressure using the procedure below. To open the purge vessel:
• Close the outlet stopcock on the purge vessel.
• Continue purging the solution with the inert gas until the flow of gas, as
indicated by the gas bubbles, has stopped or has slowed considerably.
• Close the gas inlet stopcock to stop the flow of gas into the purge vessel.
• Slowly unscrew the cap on the top of the purge vessel to release any pressure
that might have built-up during the purging.
• To drain the reducing agent, open the drain stopcock.
• To refill the purge vessel with fresh reducing agent.
• Close the drain stopcock, add 4 to 6 mL of acetic acid, open the gas inlet
stopcock and purge for a few minutes.
• Dissolve 50 mg of NaI or KI in 1to 2 mL of nitrite-free deionized water and add
the solution to the purge vessel along with 100 µL of the dilute antifoaming
agent.
• Replace the screw cap and septum, the open the outlet stopcock and purge for
a few minutes before analyzing water blanks, then samples or standards.
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