INJECTORS
Purge & Trap
Theory of Operation
TheSRIPurge&Trapusesa10port
gas sampling valve and dual adsorbent
traps. Each trap has independent
adsorption and desorption setpoints to
optimizetheanalytetrappingandreleasing
fromeachadsorbent.
When the valve is in the LOAD
position, thesample-ladenpurgegasfrom
thetesttubeorVOAvialisdirectedthrough
the two traps, thenout tovent, loading the
traps with sample at the adsorption
temperature (30-40
o
C). In thisposition,
thecarriergasmerelyentersandexits the
valve.
Afteraperiodof timesufficientfor the
traps to reach desorption temperature
(200
o
C), the valve is actuated to the
INJECTposition. IntheINJECTposition,
thecarriergas flows through the traps in
thedirectionopposite to thesample-laden
purgegas flowwithwhich the trapswere
loaded. The carrier gas backflushes
desorbedanalytes into thecolumn,while
thepurgegasflowsout tovent.
ThevalveremainstheINJECTposition
for theoptionalbakecycle,duringwhich
therespectivedesorption temperaturesof
both traps are raisedanadditional 50
o
C,
and the purge gas polishing filter is
reconditioned. A relativelyhigh flowof
purgegassweepsthroughthehotpolishing
filter,whichheatswheneverTRAP1heats.
Thispurgegasflowsweepscontaminants
fromthepolishingfilterandouttovent.
Thevalveisthenacutatedbackintothe
LOADposition,TRAP1andthepolishing
filter heat are turnedOFF, followed by
TRAP2, then thepurgegas(see theEvent
Tableonthe
GeneralOperatingProcedures
page.)
Trapheating,valverotation,andpurge
gas control are automated through the
PeakSimpledatasystem.
Purge&TrapValve in the INJECTPosition
Purgegas in
frompurge
EPCand
solenoid
Out toOn-column
injectorandcolumn
Carriergas in from
carrierEPC
Vent to
atmosphere
Heliumornitrogen
purgegasbubbles
through the
sample in the tube
SAMPLE
VIAL
10PORTVALVE
Purge&TrapValve in theLOADPosition
Purgegas in
frompurge
EPCand
solenoid
Out toOn-column
injectorandcolumn
Carriergas in from
carrierEPC
Vent to
atmosphere
Heliumornitrogen
purgegasbubbles
through the
sample in the tube
SAMPLE
VIAL
10PORTVALVE
