CALIBRATION OF pH METER SOP

5.4  Calibration of pH meter

Frequency : Daily (Prior to use)

5.4.1  Before starting the calibration make sure that the correct measurement mode is selected.

5.4.2  Wash the electrode thoroughly with de-Ionized water or a rinse solution. Do not wipe the electrode; this causes a build-up of electrostatic charge on the glass surface.

5.4.3  Maintain the temperature of the buffers to 25°C ± 2°C, unless otherwise specified in the individual monograph and dip the electrode along with the temperature sensor into the buffers.

5.4.4  Perform the five point calibration using standard buffers of pH 1.68, 5.01/5.00, 7.00/7.01, 10.00/10.01 and 12.45.

5.4.5  Dip the electrode into the calibration buffer. The end of the electrode must be completely immersed into the sample. Stir the electrode gently to create a homogeneous sample.

5.4.6  Press CAL/MEAS key to enter pH calibration mode .The CAL indicator will be shown. The primary display will show the measured reading while the smaller secondary display will indicate the pH standard buffer solution reading.

5.4.7  Wait for the measured pH value to stabilize.

5.4.8  Press HOLD/ENTER key to confirm calibration. The meter is now calibrated to the current buffer.

5.4.9  Fist rinse the electrode with de-ionized water, which is followed by next buffer solution and

place it in the buffer solution.

5.4.10  Follow steps 5.5.5 to 5.5.9 for additional calibration points.

5.4.11  When all the calibration points set in the unit configuration set up are completed the meter returns to the measurement mode automatically. However calibration can be terminated without completing the number of points as set in the unit configuration. It can be done by pressing CAL\MEAS to return to pH measurement mode. Record the calibration details and Temperature.

5.4.12  Change the calibration buffer every week or whenever required and record.