PH220A EXTECH [Extech Instruments Corporation.], PH220A Datasheet - Page 8

• Manufacturer Part Number: PH220A
• Description: Waterproof Palm pH Meter
• Manufacturer: EXTECH [Extech Instruments Corporation.]

Electrode Maintenance and Troubleshooting
Most pH measurement difficulties are caused by the electrode. Careful handling and proper
storage of the electrode will increase measurement accuracy and electrode life.
Electrodes should be rinsed to remove all traces of storage solution, process medium, or
previous test solution.
Electrode Storage
Electrode Cleaning
Troubleshooting an Electrode
Symptom
Long response time or
reading drift
Dry Bulb
Static Charge
Same readings in different
buffers and samples
Erratic LCD display
The electrode should be stored in a soaker bottle or wetting cap filled with pH4 buffer.
Never store an electrode in distilled or deionized water as this will cause migration of the fill
solution from the electrode.
The type of electrode coating that occurs over time will determine the cleaning method.
Soft coatings can be removed by vigorous stirring or by using a squirt bottle. Organic
chemical coating (hard coatings) should be chemically removed. Only in extreme cases
should the bulb be cleaned mechanically.
Cause
Clogged Junction
Strong Alkaline measurement
Deteriorated Gel layer
Protein coating on electrode
surface
Oil, paint, dyes, suspended
solids etc. are on sensor
Organic solvents are coating
the sensor
Dehydrated membrane
Long term storage without
wetting
Wiping electrodes
Cracked or broken bulb
Samples have low ionic
strength (lacks salt); e.g.
distilled, de-ionized, boiled,
lake water (high pressure)
8
Soak in 4.07 M Potassium Chloride (KCl)
Soak in 0.1 M HCL overnight.
Replace electrode. Use bulb guard. Avoid
Recommendation
@ 60
Replace electrode.
Soak in 1 gm Pepsin dissolved in 100ml of
0.1 m HCL for 30 minutes or as needed.
Rinse electrode alternately with a materials
solvent and a buffer 7.00.
Organic mole fraction has to be less than
50% to assure reasonable readings. Limit
time of measurement. Keep probe in the
7.0 buffer between readings.
Read solution for dry bulb below:
Soak electrode tip in wetting cap filled with
1ml 7.00 buffer for 24 to 48 hours
Rinse electrode in 7.0 buffer and blot. Do
no wipe electrode.
plunging electrode to bottom of container
and spinning bars. Wetting cap will protect
bulb between tests.
For each 50 ml of sample add 1 drop
(50uL) of SAT. KCl (No alteration in pH will
occur using inert KCl).
o
C for 30 minutes.
Model PH220 Version 3.1 11/2005