YSI 60 - Manual (Page 18)

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5. Maintenance of the pH Sensor
5.1 pH Sensor Precautions
1. When making measurements or performing the calibration procedure, make certain that the
level of sample or pH buffer is high enough to cover both the pH and temperature sensors.
2. Rinse the probe with deionized water between changes of calibration buffer solutions.
3. During pH calibration, allow the sensors time to stabilize with regard to temperature
(approximately 60 seconds) before proceeding with the calibration protocol. The pH readings
after calibration are only as good as the calibration itself.
4. Clean and store the probe according to the instructions found below.
5.2 pH Sensor Cleaning
Cleaning is required whenever deposits or contaminants appear on the glass pH sensor. Unscrew
and remove the small guard that protects the pH sensor. Use tap water and a clean cloth or lens
cleaning tissue to remove all foreign material from the glass sensor.
If good pH response is not restored by the above procedure, perform the following additional
procedure:
1. Soak the probe for 10 to 15 minutes in clean water containing a few drops of commercial
dishwashing liquid.
2. GENTLY clean the glass bulb by rubbing with a cotton swab soaked in the cleaning solution.
3. Rinse the probe in clean water, wipe with a cotton swab saturated with clean water, and then
rerinse with clean water.
If good pH response is still not restored by the above procedure, perform the following
additional procedure:
1. Soak the probe for 15 to 30 seconds in one molar (1 M) hydrochloric acid (HCl).
2. GENTLY clean the glass bulb by rubbing with a cotton swab soaked in the acid.
3. Rinse the probe in clean water, wipe with a cotton swab saturated with clean water, and then
rerinse with clean water.
4. Reinstall the small guard that protects the pH sensor.
If biological contamination of the reference junction is suspected or if good response is not
restored by the above procedures, perform the following additional cleaning step:
1. Soak the probe for approximately 1 hour in a 1 to 1 dilution of commercially-available
chlorine bleach.
2. Rinse the probe with clean water and then soak for 1 hour in clean water to remove residual
bleach from the junction.