The PAN GC is a custom-built gas chromatograph with electron capture detection (Ai Qualitek, Cambridge, UK). The This instrument is regularly used on the FAAM BAe 146 research aircraft.
The outputs include: the mixing ratio of peroxy acetyl nitrate (PAN).
Air samples are drawn from the main sampling manifold of the aircraft via a metal bellows pump (outlet pressure of 15 psi). Containing a dual channel separation and detection system with staggered loop injection, this instrument achieves a time resolution of 90 s and a detection limit (concentration corresponding to a signal three times the noise level of the background) of 5 pptV. The expanded uncertainty of the measurements (± 2 σ) for atmospheric mixing ratios in the low pptV to mixing ratios at the ppbV level is less than 5 % on both channels.
Within the instrument, air is drawn into one of two thermostated and pressure-monitored 2 ml sample loops by a small diaphragm pump housed within the GC. Each analysis channel is equipped with a fused silica capillary column system comprising a 10 m pre-column and a 30 m analytical column (both columns have a 0.53 mm i.d. SPB-5, 1.5 micron film thickness). An electrically-actuated 10-port valve provides a back-flush facility from the pre-column, ensuring that more retained compounds do not enter the analytical column and interfere with subsequent analyses. After 90 s flushing, the analytes in the sample loop are swept onto each column in a flow of argon carrier gas. Both the column system and sample loops are thermostated in a Peltier cooled oven at 25 ºC. The instrument is equipped with two ECDs mounted in a thermostated enclosure at 50 ºC. Argon gas is also used as the ECD make-up gas. Moisture is added to the Argon gas line via a hydrated copper sulphate trap which helps to improve the baseline stability.
|keywords:||peroxyacetyl nitrate mixing ratio, york-pan-gc|
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|Further information on the AMF website|