Bio-Rad BioLogic Signal Import Module (SIM) - Manual (Page 199)

11.4 MAINTENANCE OF THE UV DETECTOR AND THE CONDUCTIVITY FLOW CELL
The following two sections discuss the cleaning of the UV detector and the Conductivity flow cell and
replacement of the lamp in the UV detector.
11.4.1 Cleaning the UV Detector and the Conductivity Flow Cell
Cleaning of the UV flow cell is indicated when the baseline is very noisy or unstable yet air bubbles have
been removed from the flow cell. However, problems with UV detection during medium pressure
chromatography are often solved by a few simple precautions. Air bubbles trapped in the flow cells give rise
to a “sawtooth” signal pattern that will never stabilize. We recommend always running with a backpressure
regulator after the detector (if using low pressure columns, place the backpressure regulator between the
pump outlet and mixer). Equilibrate the column for at least 30 minutes to allow all bubbles to clear. Always
degass buffers before use.
Make sure all fittings are tight to prevent leaks. If liquid leaks down between the flow cell and the optics
module case, the cell should be removed and dried with a stream of pure nitrogen (never use compressed
air). The case should be dried using a warm air blower or left for several hours to completely dry.
Air bubbles trapped in the Workstation pump give rise to erratic flow rates that are sometimes interpreted as
problems with the UV detector. Refer to the previous section.
If cleaning of the UV detector and the Conductivity flow cell is desired, note the following:
• Filters: The standard filter tray contains both a 280 nm and a 254 nm filter. To clean the filters,
loosen the filter’s thumbscrew and lift out the filter holder. The filters should be cleaned only when
necessary using a dry lens tissue. To remove greasy fingerprints, use dilute ethanol or isopropanol
solutions.
• UV Flow Cell: To remove the flow cell, undo the flat bottom fittings at the top and bottom of the flow
cell. Then loosen the thumbscrews and push out the flow cell from the bottom. The flow cell is keyed
to mount in one way only, so that it cannot be incorrectly mounted. Avoid touching the quartz
windows with fingers.
If the flow cell is visually dirty, it should be cleaned with one or more of the following solvents: dilute
sodium dodecyl sulfate (SDS), 1M hydrochloric acid (HCl), 1M sodium hydroxide (NaOH), ethanol,
or acetone. Run the solution through the flow cell using a syringe and leave for no more than 5
minutes. Rinse extensively with water and then blow dry using a gentle stream of pure nitrogen.
Never dry with compressed air from a “house” line as this will contain microdroplets of oil that will
coat the cell.
When the detector is not in use, disconnect the flow cell and use a syringe filled with distilled water
to clean out traces of salts and protein.
Before storing the flow cell, inject a dilute solution (10% to 25%) of ethanol or isopropanol into the
cell to prevent microbial growth. Use the plugs provided with the flow cell to seal the flow cell’s inlet
and outlet lines.
• The Conductivity flow cell requires little maintenance other than rinsing routinely with deionized
water.
MAINTENANCE MAINTENANCE AND TROUBLESHOOTING
11-6