pH Measurement Theory vol3

Problems which arise during pH measurements can have different sources; from the meter, cable and electrode, down to the buffer solutions, measuring temperature and sample (application). Special note should be taken of the symptoms of the problem as these are useful for locating the origin of the fault. The following table gives an overview of symptoms and causes:

Readings too high/too low or off-scale readings “—”

• Check meter, cable, electrode, calibration procedure and sample temperature

Value does not change

• Check meter, cable and electrode

Slow response time

• Check electrode and sample/application

High offset after calibration

• Check electrode, buffer solutions and calibration procedure

Low slope after calibration

• Check electrode, buffer solutions and calibration procedure

Calibration error

• Check meter, cable, electrode, buffer solutions and calibration procedure

Drifting measurement values

• Check electrode and sample/application