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6
Routine Maintenance
Cleaning the LightPipe Flow Cell
90
Surveyor PDA Plus Detector Hardware Manual
Thermo Scientific
4. Flush the cell with water to prevent a reaction between the cleaning solvent and the
mobile phase that is used in your application.
5. See
“Installing the LightPipe Flow Cell”
for instructions on how to reinstall
your LightPipe.
Cleaning the Flow Cell with Nitric Acid
Isopropanol or methanol is generally sufficient for cleaning a LightPipe. However, if the
LightPipe remains contaminated after flushing it with organic solvents, perform the following
procedure using nitric acid.
To clean the LightPipe with nitric acid
1. Completely remove the LightPipe from the detector housing by following the procedure
in
“Removing the LightPipe Flow Cell”
. (This prevents possible leaks from
harming the mechanical and electronic components of the detector.)
2. Ensure that the column is removed from the chromatographic system to avoid column
degradation. Connect the LightPipe inlet directly to the chromatographic pump.
3. This step is very important! Flush the LightPipe with water to prevent a reaction between
the last solvent used in the chromatographic system and the nitric acid solution that is
going to be used to clean the cell.
4. Prepare a 20% (v/v) solution of nitric acid in HPLC-grade water.
5. Pump the nitric acid solution through the LightPipe using the chromatographic pump.
6. After you have finished the cleaning procedure and before you return to the
chromatographic solvents, pump another 25 to 40 mL of water through the flow cell to
remove all traces of nitric acid. Monitor the pH of the outlet stream of the LightPipe to
ensure that the acid has been completely flushed out.
CAUTION
Nitric acid is a strong oxidizing acid, and it can react vigorously with alcohols
(especially methanol). Be sure to wear protective clothing and eye protection and adhere
to safety procedures at your company for the proper handling and disposal of corrosive
acids. Flush the flow cell with water to remove all traces of alcohol before flushing it with
nitric acid.
CAUTION
Thermo Fisher Scientific does
not
recommend using a syringe to force
acid solutions through the flow cell. Pressurizing the syringe could cause a leak or
rupture, resulting in a dangerous and uncontrolled spraying of acid.
CAUTION
Ensure that the column has been removed from the chromatographic
system and that water was the last solvent in the pump and solvent reservoir before
you pump nitric acid solution through the LightPipe flow cell.