POPULAR CONFIGURATION GCs
Multiple Gas Analyzer #1
Theory of Operation
10-PortGasSamplingValvePlumbingConnections
Thesample isdepositedby thecarriergasstreamfirst into theSilicaGelcolumn,with thecolumnoven
holdingat40
o
C,wheretheethane,propane,butanes,pentanes,andcarbondioxideareretained. Theremainder
of thesamplecontainingH
2
(orhelium,whichever isnotbeingusedasacarrier),O
2
,N
2
,methane,andCO,
continueson to theMolecularSievecolumn. Duringachromatographicrunwith thesamplingvalve in the
INJECTposition, theH
2
orhelium,O
2
,N
2
,andmethanecomponentsarethefirsttoelutethroughthecolumns
and into thedetector. This isdue to theSilicaGel’s long retentionofC
2
,CO
2
andhigherhydrocarbonsat
40
o
C. Thesamplingvalve isactuatedback into theLOADposition immediatelyfollowing theelutionof the
COpeak. Thisreversesthesequenceofthecolumnspriortothedetector,andsendsthecomponentspreparing
toelute from theSilicaGel packedcolumn (ethane, propane, etc.) to thedetectorwithout passing them
through theMolecularSievepackedcolumn. At thesame time, theSilicaGelpackedcolumn is temperature
ramped topromote therapidelutionof theremainingcomponents.
Thebuilt-indatasystemautomatestheprocess:thecolumnoventemperatureiscontrolledthroughaPeakSimple
temperatureprogram,and thesamplingvalve iscontrolled throughaPeakSimpleevent table.
Event table:
Time Event
0.000 ZERO
0.050 GON(valve in INJECT)
6.000 GOFF (valve inLOAD)
Temperatureprogram:
Initial
Hold Ramp Final
40
o
C 4.00 20.00 220
o
C
220
o
C 10.00 0.00 220
o
C
After theelutionof theCOpeak, thevalve
isswitchedback into theLOADposition,
and theC
2
,CO
2
,andhigherhydrocarbons
comeoff theSilicaGel column.
