Chapter:
PURGE-AND-TRAP
Diagnostic Flowchart
Topic:
Troubleshooting Purge
and
Trap
Contamination
Page 1
of
2
Is the
to-port
gas sampling valve oven temperature set
and
operating
above
150°C?
Set
valve
oven
temperature
above 150°C
and perform
2
blank
runs.
Does the
contamination
persist?
Contamination
problem has
been
resolvecl.
The
concentration
is below 0.5
ppb
(1120
of the area obtained from a
10
ppb
staneard).
This level of
background is acceptable and
insignificant
and will
not adversely
affect your analysis.
Determine the concentration
of
the contamination.
Compare
its
area to the area obtained from a 10
pPJ
standard analysis. Is the concentration of contamination
significant
(>
1120 of 10
ppb
[0.5
ppbl
)?
Tum
ott
the sparge gas
pressure
(set to a
psij.
After
perlorming two blank analyses,
are the contamination
peaks
still a problem?
Use this
troubleshooting
flowchart
ff
you are
experiencing
difficulty with
contamination
when perfonning
purge and
trap
analyses.
Tum the sparge gas pressure
back to normal setting
(4-5
psij.
Bake
out
the polishing
filter. Then
run
2
clean
water
blanks.
Is contamination still
a
problem?
Proceed to
page 2 of
the
diagnostic
flowchart.
Repeat the cleaning
of the complete
sparging
apparatus,
including the
water
trap.
This should
eliminate the
problem.
Contact SRI
Instruments
for
technical assistance in
diagnosing this
condition.
Localized
heal
cleaning
resolvecl
the
problem.
Replace the entire sparging
apparatus
with
a section of clean
tubing.
After
performing two more
blank runs, is the contamination
still a problem?
Using a heat gun, heat the entire sparge
head
assembly
with the sparge head's
injection
port
nut removed while sparge
gas is
flowing.
After
perlorming a blank
analysis, is the contamination still a
problem?
Clean the sparge head,
backtlow
trap
and
air gas lines
in between. Then make two
blank runs. Is the contamination
still
a problem?
The contamination.
now
insignif.cant,
was
located in the
area
of
the sparge! backflow
heads
and/or related
tubing.
The
contamination.
now reduced to
anacceptable
level,
appears
to
havebeen
accumulated on
the poishing
filter. The
poishing fitter
should
be
baked-out
periodically
as
part
of
routine
preventitive
maintenance.
