10Station Purge-and-Trap Autosampler
PURGE-AND-TRAP
Chapter:
Topic:
(- - - - - - - - - - - - - - - - - -1
l
J
<,
Right
bank
of
5
sparge
heads
Manual remote control
with
5JO0
°
digital
position
display
and
__.@
@
momentary
stepping
I
home
•
@
toggle
switch
@
o
°
-·""-·-,,iiI
~
remote
cootrol
wand
-:
Left
bank
of
5
sparge
beads
The SRI 10Station Purge-and-Trap Autosampler
permits
the unattended sparge, concentration,
andanalysis of up
to
10 separatewater and
I
orsoil-in-water samples, whenusedinconjunction
with
theSRI EPA-Style Automated Purge-and-Trap Sample Concentrator option available as a built-in
option for
all
SRI 8610Cgas chromatographs. The PeakSimple data system (or other data system
offering
timed
event control of external events
via
relays) is required forautomated operation of this
system. Manual controls are
also
provided for
direct,
manual control by
the
analyst, including a remote cabled
sample position stepping control
that
features a digital LED display of the
sample position
in
use. The toggle
switch on thiscontrol
has
two
momentary-on positions. Pushing the
toggle switch
to
the upmomentary-on
position causes the automated sample
streamselection valve
to
step
to
the
next sample
in
order. Pushing the
toggle switch down causes the
sampling valve
to
return
to
thehome
(sample sparge head I) position. The
sample sparge headsarenumbered
according
to
their sampling order. A
stainless steel knurled fining holds the
disposable glass sample tubes in place.
Teflon ferrules in the knurled fining
seal
the sample tubes in place,
preventing gas
leaks.
10STATIONPURGE-AND-TRAP AUTOSAMPLER SIDEVIEW
Only twogas connections are
needed to supply the autosampler with sparging gas, and to deliver the sample-laden sparge gas to the
purge-and-trap sampler's dual trap concentration system. Thesetwo
gas
lines replace the sparge head
assembly on the EPA-style purge-and-trap system, A remote control signal cable connects the
autosampler valve control electronics
to
the
data
system external event control circuitry. This simple
cable requires only three connections to the
data
systemeventcontrol relays, common, step, and
home. The
data
systemmust provide amomentary closure between the common wireand one of the
two
action wires
to
move the streamselection valve
to
thedesired position.
Any of the
to
sample vessels may also be
used
to
contain a clean water blank (or
air)
for use
between analysesforblank runs. The stream selection valvemust
be
stepped
to
this blank position,
and then to the desired sample position for blank operation. A large volume headspace samplemay
also
be
introduced into the systemfor concentration ontothe dual adsorbent traps, as each sparge
head is
equipped
with a
gas
injection port for manual syringe injections.
In
this manner, a 5Occ,
l(X)cc, or larger volume headspace sample can
be
passed
through the traps, inorder
to
acheive low
sample detection levels unattainable
by
regular headspace injection on-eolurnn using standard
microliter tomilliliter volumes. Thesparge gas supply should
be
turned on toassist the
injected sampleto flowthrough the
traps
when this feature is used.
