Siemens PGC 302 Edition II - Page 200

3. Preadjustment of differential pressure
If possible:
Set the differential pressure to 20 mbar using the capil-
lary. To do this, switch MV
Cut
ON and connect a press-
ure gauge to the four-way distributor (on left and right
of MV
Cut
). Your advantage: you need fewer attempts in
the next step.
4. Adjustment of flow through the
coupling capillary in position
Straight
MV
Cut
ON MV
Back
ON
Target To pass the measured peak completely via
column B to the detector, and just no longer
to the outlet
Purge outlet
.
Measure Increase the flow in the coupling capillary
until it no longer completely passes into
column B. Then close NV
Straight
in steps of
e.g. 1/2 revolution until a peak appears at the
outlet
Purge outlet
.
Then open NV
Straight
again carefully until the
peak just disappears.
5. Adjustment of flow through
column A in position
Straight
MV
Cut
ON MV
Back
ON
Target To pass the measured peak completely to the
detector via column B, and just no longer to
the outlet
Cut outlet
.
Note If you do not have a monitor detector, you
must replace the capillaries here as described
in
There are three outlets
!
Is there a peak at the outlet
Cut outlet
?
YES NO
P
A
is too high, and thus also
the flow through column A.
Not everything passes into
the coupling capillary.
Reduce P
A
until the peak
just disappears.
This is right!
But the flow through column
A could be smaller than
necessary. Therefore test:
Increase P
A
until a peak
appears at the outlet
Cut
outlet
.
Then reduce P
A
again
carefully until the peak just
disappears.
6. Adjustment of flow through the
coupling capillary in position
Cut
It is also useful to adjust the differential pressure to -20
mbar prior to this step. You then need fewer attempts in
this step.
IMPORTANT
From now onwards: don’t touch P
A
, P
M
,
NV
Straight
MV
Cut
OFF MV
Back
ON
Target The measured peak should just no longer
arrive at the detector following column B; it
should be completely at the outlet
Cut outlet.
Is there a peak at the detector via column B?
YES NO
The flow through the
coupling capillary is too
small, sample is still coming
through!
The differential pressure
must therefore be increased.
To do this, close NV
Cut
in
steps of e.g. 1/2 revolution
until the peak just disappears.
This is right!
But the flow through the
coupling capillary could be
higher than necessary.
Therefore test:
Open NV
Cut
in steps of 1/2
revolution until the peak just
appears.
Then carefully close NV
Cut
again until the peak just
disappears.
NOTE:
If you are working with a temperature program, you should
adjust step 5
Straight
at the lowest temperature, but step 6
Cut
at the highest temperature!
If you do not have a monitor detector and have therefore re-
placed the capillaries in step 5, you must now change them
back again!
7. Adjustment of position
Backflushing
MV
Cut
ON MV
Back
ON
Target Measured peak must not arrive at the detector,
it must pass completely into open air via the
backflushing outlet.
Adjust NV
Back bypass
to 5 ... 10 ml/min at the outlet,
but at least a little more than flows through
column A.
Inject test substance. A peak must not appear on the
detector!
A
A
A
Adjusting the live switching
live.chp, Issue August 17, 1999
6 - 9