Hach-Lange POLYMETRON 8350_8351 Basic User Manual - Manual (Page 7)

pH
Refer to the pH transmitter user manual to select the type of calibration.
1. Rinse the probe with the freshly prepared first buffer solution (pH 6.88 or 7.00) ideally at the same
temperature of the measurement sample.
2. Immerse the probe to a depth of 4 to 5 cm and wait for stable measurements (pH and temperature)
before calibrating.
3. Rinse the probe, first with demineralised water and then with the second buffer solution (pH close
to that of the process, 4.00 or 9.22).
4. Immerse the probe to a depth of 4 to 5cm and wait for stable measurements (pH and temperature)
before calibrating.
5. Rinse the probe in demineralized water.
Redox
1. Rinse the probe with a freshly prepared standard quinhydrone solution ideally at the same
temperature of the measurement sample.
2. Immerse the probe to a depth of 4 to 5 cm and wait for stable measurements before calibrating.
3. The measured potential is defined with respect to the Ag/AgCl reference system. Add 200 mV for
an E
H2
reference potential.
Cleaning and regeneration
These electrodes are considered as consumable items and therefore have a limited lifespan, largely
dependant on the application. Under normal conditions a typical lifespan would be about one year.
Before replacing them, however, simply cleaning the electrodes may regenerate them.
Such cleaning will be necessary whenever the following are observed:
• An offset from zero or a measurement drift (the reference system is contaminated)
• A significant drop in response time and a loss of slope (glass diaphragm or platinum ring dirty)
Provided the glass diaphragm is neither scratched nor cracked, follow one of the cleaning procedures
below:
• Salt deposits: HCl 0.1M (5 mins) + NaOH 0.1M (5 mins)
• Grease or oil film: Detergent + water
• Reference junction dirty: KCl 3M @ 60-80°C for 10 mins, then cool in KCl 3M @ 25°C
• Calcium, metal hydroxide or protein deposits: HCl 10% for 10 mins
• Deposits, wear on redox measurements: Aqua regia (1/1 concentrated HCl / concentrated HNO
3
).
This process must only be carried out by qualified individuals.
If the electrode response is still not improved, replace it.
Storage
• Never store the probes in air or with a dry protection cap. Moisten the cap with KCl 3M
• Storage temperature: 10 to 30°C
• Typical duration: 6 months
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