GC measurements

An Agilent 6890N gas chromatograph (GC) based analytical system was installed in Hegyhátsál in 26-27 January, 2006. Air samples are taken from 96m elevation. Using ECD and FID sensors the mixing ratio of CH4, CO, N2O and SF6 are monitored continuously.

System description:

Auxiliary system components:

Hydrogen generator: Parker Balston: Mod.: 9090
Air compressor: Jun-Air Mod.: OF-302-25B x 2
Zero Air generator: Parker Balston Mod.: 75-83-220
N2 generator: Parker Balston Mod.: 76-92-220
We had problems with the latter model, since there was no catalyst for hydrocarbon (especially methane) removal. To establish the optimal condition for the N2 generator we dried the compressed air with an adsorption dryer, Mod.: HL-S0120, but this did not decrease the methane concentration in the generated nitrogen. To solve the problem, we use compressed nitrogen, with purity of 99.99990% (6.0).

Sampling system:

Pump: KNF Neuberger, Mod.: N86ATE (special version)
Miniature pneumatic supply - constant pressure and stream splitter
Dryer at about -90 deg.C
Valco 10 position sampling valve with microelectronic controller

Summary of the system:

Instrument principle: GC
Manufacturer: Agilent
Type: 6890N
Acquired: 2003
Sample flow: approx. 150 ml/min
Reference flow: approx. 150 ml/min
Sample period: 10 mins
Flush time: 0.5 mins
Calibration freq: 12 hours
Target freq: 0.3 hours
Column A: Unibeads+mol.sieve 5A 1/8 inch,4+6 feet
Column B: Hayesep Q 1/8inch 4+6 feet
Measurements stored 6 per hr
Levels: 96 meter AGL

The GC system in operation at the measurement site

Schematic diagram of the Agilent 6890N setup (Figure by courtesy of Cyril Messager, LSCE)

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