GC INJECTORS
Model 8640 20-Vial Integrated Liquid Autosampler
Theory of Operation
Liquidsample issealed intovapor-tightvialswhichare inserted into thesample tray. The tray is then
inserted into theModel8640assemblyandpositionedfor thesamplingsequence. The8640uses60psiofair
ornitrogen toactuate itsmovingparts.
Thesamplingprobe,aconcentric
needle, ismoveddownbyapiston to
pressurizethevialwithheliumorother
gas,causingsampletoflowthroughthe
injectionsyringeandout theTeflon
TM
tubingintothewastebottle. Thesample
probepressurizes thesamplevial fora
periodof time longenough torinse the
previous sample towasteand fill the
syringewithsample.
Thesyringemechanismbeginsthe
process in thefullyretractedposition
(1). Inthisposition, thesampleflows
through the barrel of the injection
syringe, through the needle to the
wastedivertervalveandintothewaste
bottle. Afterapproximately0.5mLof
sampleisflushedtowaste,thesyringe
barrel is filled with sample. The
syringemechanism is thenmoved
forward by a piston, so that the
syringeneedlepenetrates thewaste
diverter seal, then theGC injection
port septum (2). Once the injection
needlehaspenetratedtheGCinjection
porttothefulldepth,thesyringebody
is pushed forwardover theneedle,
displacingthesampleintotheinjection
port (3). Once thesamplehasbeen
injected, the syringe mechanism
retracts,withdrawing from theGC
injectionport.
Sample flow
out to
syringe
Pressurizing
gas in
Gasvent
Probe
Sampleprobe
piston
Samplevial
Septum
SamplingProbe Sequence
InjectionSequence
1-
Load
2 -
Carriage forward
3 -
Inject
GC injection
port
Sample in
from sample
probe
To waste
Waste diverter
