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4.5. Considerations:
4.5.1. Calibration times of meter rely on the sample, electrode performance and required
accuracy. For high accurate measurement (
≤
±0.02pH), which should be calibrated
immediately with high accurate standard buffer solution, for general accuracy
measuring (
≤
±0.1pH), which can be used almost one week or long time once be
calibrated.
4.5.2. The meter must be re-calibrated in the following situations:
(a) New changed or unused electrode for a long time;
(b) After measuring acid (pH<2) or alkaline (pH>12) solution;
(c) After measuring solution which contains fluoride and concentrated organic solution;
(d) The solution’s temperature is much different with calibration temperature.
4.5.3. The soaking solution in the protecting bottle of front pH electrode is to keep the glass
bulb and junction activating. Loose the capsule, pull out the electrode and wash it in
purified water before measuring. Insert the electrode and screw tight the capsule after
measuring to prevent the solution leaking. If the soaking solution is turbid or moldy,
please wash and change a new one at once.
4.5.4. The preparation of the soaking solution: take 25g analytical pure KCL, dissolved with
purified water and dilute to 100mL. Electrode should avoid soaking in purified water
protein solution and acid fluoride solution for a long time as well avoid getting
touching with organic silicon lipidic matters.
4.5.5. To calibrate the meter with the given value pH buffer solution, the pH value of the
standard buffer solution must be reliable so as to improve the accuracy. Buffer
solution should be changed in time after many times using.
4.5.6. Always keep the meter clean and dry; especially for the socket of meter and electrode,
otherwise it may lead to an inaccurate measurement or invalidity. To clean and dry
them with medical cotton with dehydrated alcohol if there are any dirty.
