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APPENDIX II. CLEANING THE VISCOMETER DETECTOR IN SITU
The viscometer bridge can occasionally accumulate dirt or debris, affecting the
performance of the detector. The symptom is bridge imbalance, as measured in section . A
flush with diluted nitric acid will often clean the system and restore optimum performance.
1. Turn Off the Main Power.
2. Disconnect the tubing at the Sample Inlet Port.
3. Remove the detector drawer and connect the electrical umbilical.
4. Remove the viscometer delay column from the bridge circuit, plugging each end to prevent
air from entering. Replace it with a union.
5. Likewise, bypass the SEC columns, LS and RI dectectors from the chromatographic circuit,
replacing them also with a shunt of clean tubing.
It is very important that both the RI and
LS detectors be bypassed when using dilute acid for cleaning. Failure to do this
could damage the detectors.
6. Exchange the mobile phase with a miscible solvent and eventually distilled
H
2
O.
Purge the
detector with at least 100 mL.
7. Exchange the mobile phase with 50% HNO
3
(6M) and purge the detector with at least 200
mL.
8. Take the mobile phase back through the above stages in identical reverse order.
9. Replace the separation columns and other detectors. Test for leaks.
10. Replace the detector drawer and temperature equilibrate. Run a control.
11. Recalibrate the system.