LABEC M-MIA-LA - Manual (Page 90)

Ultrasonic milkanalyser
Operation manual 04.11.09 88/107
How long an electrode will last is determined by how well is maintained and
the pH application. The harsher the system, the shorter the lifespan. For this
reason it is always a good idea to have a back-up electrode on hand to avoid
any system down time.
3. Buffer Solutions
Buffers are solutions that have constant pH values and the ability to resist
changes in that pH level. They are used to calibrate pH measurement
system.
PH buffer solution description (Pharmacopoeia standard)
Use only these types’ standard buffers for calibration!
Description
pH 7.00±0,01/20ºC pH 4.00±0,01/20ºC
Composition Potassium dihydrogen
phosphate, Di-sodium
hydrogen phosphate
Borax, Sodium
hydroxide solution
Temperature
parameters
10ºC - 7.06
25ºC - 6.99
20ºC - 7.00
30ºC - 6.98
40ºC - 6.95
50ºC - 6.91 10ºC - 4.00
25ºC - 4.00
20ºC - 4.00
30ºC - 4.00
40ºC - 4.00
50ºC - 4.05
4. pH Electrode Calibration
pH Electrodes are like batteries; they run down with time and use. As an
electrode ages, its glass changes resistance. For this reason, electrodes
need to be calibrated on a regular basis. Calibration in pH buffer solution
corrects for this change.
Calibration is an important part of electrode maintenance. This assures not
only that the electrode is behaving properly but that the system is operating
correctly.
Usually pH meters require calibration at 2 specific pH values. One calibration
is usually performed at pH 7, second pH 5.
It is the best to select a buffer as close as possible to the actual pH value of
the sample to be measured. Use standard calibration buffers that the
temperature and the sample solution are the same.
Use the operation manual for the corresponding pH meter.