4
Maintenance
Cleaning the LDA Components without Disassembling the LDA
38
Surveyor MS Pump and Surveyor MS Pump Plus Hardware Manual
Thermo Scientific
Cleaning the LDA Components without Disassembling the LDA
Contaminated check valves and contaminated proportioning valves can cause an excessive
variation in backpressure. To remove the contamination, open the venting valve to bypass the
LC column and pump the appropriate flush solvents through the LDA.
To clean the check valves and the proportioning valves
1. Open the venting valve by turning the wingnut on the left side of the LDA
counterclockwise (see
).
2. Set up the system to pump the same solvent on all four channels by connecting all four
solvent reservoir lines to one solvent bottle.
3. Attach a 10 mL disposable syringe to the tubing attached to the vent valve. The syringe is
supplied in the MS Pump Accessory Kit (see
4. If you were pumping buffered mobile phase through the system, pump HPLC-grade
water on all four channels at a flow rate of 200
L/min for 30 minutes. Empty the
contents of the syringe into a suitable waste receptacle, and then pump an additional
6 mL of water through the LDA.
5. Sequentially pump solvents of increasing polarity through the LDA. The last flush solvent
should be miscible with the mobile phase that you plan to use.
6. Close the vent valve.
7. Retest the pressure variation by returning to the initial conditions that displayed the
problem. Make sure that the backpressure at these conditions is at least 40 bar.
Note
Opening the venting valve redirects the mobile phase out the venting valve on
the left side of the LDA rather than into the crossover tubing. If you forget to open
the venting valve, the flush solvents pass through the pulse dampener and onto your
LC column.
Table 3.
Polarity indexes of various HPLC solvents
Solvent
Polarity index
Isopropanol
3.9
Methanol
5.1
Acetonitrile
5.8
Water
9.0