PICARRO A0311 User Manual page 52

The user should determine the appropriate length for the Purge steps. Above, we
suggest a notional choice of 2 minutes based on experience that this is adequate
for bringing the sample measurement to <1 ppm CO2 even on slower flow
systems like the G2201-i. Users may find that 1 minute or even 30 seconds is
adequate for the G2508/G2308 and other instruments. The user must make their
own determination about an acceptable baseline concentration value between
samples. For some, a baseline of <10 ppm CO2 may be acceptable, while for
others a baseline of <10 ppb N2O or Ethylene may be necessary depending on
the size of the flux produced in the chambers.
The user should also determine the appropriate time for the sample steps given
the signals to be observed, the expected flux, and the speed of the biological,
chemical, or physical process.
As gases, typically CO
hours, they may eventually exceed the operating concentration range of the
instrument for a given gas. Consult your data sheet, and limit runs without
headspace purging to ensure headspace gas build-up does not lead to data
quality issues through ringdown timeouts or interference. If sweepout is desired,
CAUTION
consider the approach recommended in the next section.
52
, accumulate in the headspace of a sample jar over
2
P/N 40-0038 Rev. G
Recirculation with the A0310
A0311/A0311-S/A0310 UM