2.4. Analytical test
The compositions of raw and purified biogas were analyzed by gas
chromatography (GC-8AIT/C-R8A SHIMADZU Corporation, JAPAN).
The instrument was fitted with a Porapak N 80/100, 274 cm, a 1/8
mesh 250 × 250 × 145 mm column, a molecular sieve (mole sieve
5A 60/80, 182 cm, 1/8), a stainless-steel column and a thermal conductivity
detector. Column oven maximum temperature was 399 °C
with ±0.1 °C temperature stability. A TCD type detector made from
Tungsten Rhenium filament was employed. Maximum temperature
and sensitivity of the detector was 400 °C and 7000 mVmL/mg, respectively.
Argon (Ar) was used as the carrier gas at a flow rate of
30 mL/min. The column and the injector temperature were 60 and
80 °C, respectively with an operating current of 60 mA. Gas flow rates
were regulated using a gas flow meter. The pressure was higher than
atmospheric level and was monitored by pressure gauge. All measurements
were repeated at least three times. The lowering of CO2
concentration and enrichment of CH4 were determined by analyzing
the data obtained from gas chromatographic measurement.