He/N2 carrier gas switching

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Are gas filters an issue when switching between He & N2 carrier gas? The following Agilent installation instructions indicate a long purge may be necessary to remove the nitrogen.

"Flush the filter. Set the instrument split vent flow (purge flow) to 400 mL/min, then:
• If using a Moisture Filter in combination with an MS detector, purge the filter for at least 60 minutes. This will flush the filter of dry nitrogen so that it does not appear as a background ion in your MS analysis."
markelh wrote:
Are gas filters an issue when switching between He & N2 carrier gas? The following Agilent installation instructions indicate a long purge may be necessary to remove the nitrogen.

"Flush the filter. Set the instrument split vent flow (purge flow) to 400 mL/min, then:
• If using a Moisture Filter in combination with an MS detector, purge the filter for at least 60 minutes. This will flush the filter of dry nitrogen so that it does not appear as a background ion in your MS analysis."

Install separate filters for helium and nitrogen. Otherwise you will have mentioned problem.
Agreed, use the filters before the switching valve and you only need to purge for a few minutes to remove the nitrogen from the actual lines and injection port.

I usually let mine run for 15-20 minutes at a more normal 20ml/min split flow before starting analysis and it seems to work.
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3 posts Page 1 of 1

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