44
•
Remove the old column set and replace with an in-line HPLC filter, if one is not already
in place. The in-line filter will prevent particle contamination from the pump entering the
detector and possibly plugging up the viscometer capillary tubing.
•
Change to the new mobile phase solvent, purging continuously through the detector with
both the purge ports open. Continue until at least 60 mL of new solvent has purged
through the detector.
•
Install the new columns and continue the detector purge for at least two column-volumes
more.
•
Close purge ports and examine the baselines on the detector.
C.2 ADJUSTING ZERO OFFSETS OF DETECTOR SIGNALS
C.2.a Adjusting IP Zero
The IP zero can be adjusted by selecting the appropriate channel and pushing the zero
button on the front panel. No additional offset should be required.
It is very important to zero
the inlet pressure with flow off only.
Note: The IP measurement is treated as an “absolute” measurement by the data system, unlike
the RI and DP signals which are baseline corrected. For this reason,
the IP must never be
zeroed with the flow on
.
C.2c Adjusting LS Zero
The LS zero can also be adjusted by selecting the LS signal with the select button on the
front panel and pushing the zero button. This provides offset up to the full scale collection
setting established in the TriSEC software. Typically, this signal is zeroed with the flowrate
turned on and the laser has been on for at least 45 minutes.
Note: the typical zero reading is 10
millivolts after pressing the zero button.
C.2.d Adjusting RI Zero
The RI can be zeroed by first selecting the RI signal with the select button on the front
panel, and then by moving the RI zero switch either up or down depending on the algebraic sign
of the signal. Typically, this response is zeroed with the flowrate turned on, the detector has
been sufficiently purged, and after the temperature has stabilized overnight.
C.3 CHECKING PERFORMANCE
There are a few measurements necessary to define in order to properly check the
performance of the detectors.
