The
experimental arrangement consists of a small modification of a commercial gas
chromatograph (Figure 1), so that it includes a six-port gas-sampling valve,
and a simple cell placed inside the chromatographic oven. This cell suppresses
the effects of the carrier gas flow on the physicochemical phenomena-taking
place in the stationary phase.
Figure 1: Shimadzu
GC-14B
The
apparatus used is a conventional gas chromatograph (Shimadzu GC-14B) with a
flame ionization detector contained in its oven (Figure 2) with two sections of lengths l’ and l of
a stainless-steel chromatographic column containing no chromatographic
material. The empty stainless steel is a ¼ inch chromatographic tube with 4 mm
internal diameter and length, L= 28.5
cm and l=l’=57 cm. They are connected at the junction x=l’ by a ¼ inch Swagelok
tee union. Another sample ¼ inch union is used to connect a short tube (2 cm)
containing 4 ml of liquid at the end of diffusion column L.
Figure 2: Instrumentation
of the reversed flow gas chromatography technique for the simultaneous
measurement of the diffusion coefficients and rate transfer coefficients of the
evaporating liquids.
A
stainless-steel diffusion column, consisted of the section z, was connected perpendicularly at its upper end to the middle of
the column l’+l (57 cm+57
cm). The reactant (AR Grade) was injected at a middle point of the
column as the stationary phase, and the direction of carrier gas flow was
reversed from time to time instead of stopping it. This created extra chromatographic
peaks ‘sited’ on the continuous signal. At the end of sectiozn is located a container, in which the
liquid was contained. The end D1 of the sampling column l’+l
was connected, via a six-port valve, to the carrier gas (nitrogen) supply, while
the other end D2 was connected to the flame ionization detection
(FID) system. After waiting for the monotonously rising concentration– time
curve to appear in the detector signal, we started the chromatographic sampling
procedure by reversing the direction of the carrier gas flow for 6 s, which is
a shorter time period than the gas hold-up time in both column sections l
and l’. When the gas flow was restored to its original direction, sample
peaks were recorded. The pressure drop along l+l’ was negligible
and the pressure inside the whole cell was 1 atm. The carrier gas flow-rate was
kept constant (1.0 cm3 s -1).
Figure 3: Internal close-up of the RF-GC
system
Reference:
Mohammad, H. H., Mohd. Zain, S., Atta Rashid, K., &
Khalid, K. (2013). Study the Effect of Imposing Surfactants toward the
Evaporation of Low Molecular Weight Alcohol. International Journal of Environmental Science and Development, 4(4),
5. doi: 10.7763/IJESD.2013.V4.381
