INJECTORS
Heated Static Headspace Injector
Theory of Operation
TheSRIHeatedStaticHeadspace
Injectorusesamechanicallyagitated
heaterbodyforsampleequilibration,a
10portgassamplingvalvewitha1mL
sample loop, andasample loopshut-
off solenoid valve. The headspace
analysis begins with the sample
equilibrationperiod,duringwhich the
gas sampling valve is in the LOAD
position. A40mLVOAvialcontaining
10-20mLofsamplematrix is inserted
into theheaterbody, thenheatedand
agitated (the time it takes to achieve
equilibrationdepends on the sample
matrixand the target analytes). Two
needles in theupperpartof theheater
bodypuncture the septum topof the
vial inorder todeliverpurgegas into
and route the sample out of the vial.
After theequilibrationperiod, thevial
ispressurizedso that thesamplewill
escapewhenthesolenoidshut-offvalve
isopened. Theamount of purgegas
needed to pressurize the VOA vial
dependsupon the typeof sample. A
samplewith high liquid content can
create sufficient pressure during the
eqiulibrationperiod to fill thesample
loopwithheadspace. Adrysamplewill
require that the purge gas be turned
ON, up to 10psi, to pressurize the
samplevial. Thesolenoidshut-offvalve
atthedownstreamendofthe1mLloop
is then opened briefly, and the
pressurizedheadspacesamplefills the
loopasitexitsthroughthevalve. After
the shut-off valve closes, the gas
sampling valve is actuated to the
INJECTposition,placing thesample
loop in thecarriergasstream tosweep
the headspace sample into the GC
column,andon to thedetector(s).
VOAvial
Purgegas in
fromspargeEPC
Carriergas in from
carrierEPCand
polishing filter
Tocolumn
Sample loop
shut-offvalve
Vent to
atmosphere
1mLsample
loop
Sample
Headspace
Heaterbody
Valve in INJECTPosition
Purgegas in
fromspargeEPC
Carriergas in from
carrierEPCand
polishing filter
Tocolumn
Sample loop
shut-offvalve
Vent to
atmosphere
1mLsample
loop
Sample
Headspace
Heaterbody
VOAvial
Valve inLOADPosition
