Operation and Calibration of pH meter

1.0    OBJECTIVE:  

To lay down the procedure for  Operation and Calibration of  pH meter.

2.0    SCOPE:

This SOP is applicable to the Operation and Calibration pH meter used in Quality Control Department.

3.0    RESPONSIBILITY: 

Officer-Microbiology for operation and Calibration.

Head-QC for compliance.

4.0    PROCEDURE: 

4.1    Switching ‘ON’ and ‘OFF’ of the pH meter :

4.1.1    Ensure the pH meter is perfectly grounded to electrical supply, otherwise slow response of electrode takes place.

4.1.2    Plug the RTD  probe and electrode into the sockets provided.

4.1.3    Switch on the main power supply and power “ON / OFF ” key at the rear of the unit.

4.1.4    After switching on the pH meter, LABINDIA INSTRUMENTS PH Meter will be displayed on LCD

4.1.5    Press “RESET” key and the instrument shall be in the stand by mode .  

4.1.6    Selecting the Required Measuring Mode :

4.1.7 By Pressing “MODE” key to enter into programme mode.and  1st “pH MEASURMENT” mode will be display on LCD.

4.1.8    By Pressing “MODE” key  2nd time “ mv MEASURMENT” mode will be display on LCD.

4.1.9    By Pressing “MODE” key  3rd  time  “PROBE CHECK”  mode will be display on LCD.

4.1.10    By Pressing “MODE” key  4th time “CALIBRATION PARAMETER” mode  will be display on LCD.

4.1.11    By Pressing “MODE” key  5 th  time” DATE & TIME “mode will be display on LCD.

4.1.12    By Pressing “MODE” key  6 th   time “PASSWORD MODE” will be display on LCD.

4.2    pH / mV Measurement :

4.2.1    Ensure that the pH meter is calibrated.

4.2.1.1    Switch on the instrument and select the mode of operation as described in 4.1.1 to 4.1.5.

4.2.1.2    Remove the electrode from the pH 4.00 buffer / distilled water beaker. Wash the electrode thoroughly with distilled water. Wipe the electrode with tissue paper.

4.2.1.3    Place the beaker with sample beneath the electrode and stir well.

4.2.1.4    Select the required measurement mode (pH or mV) by pressing “MODE” key. 

4.2.1.5    Wait till the temperature display on LCD is stabilized

4.2.1.6    Press the “MODE” key once again.

4.2.1.7    The pH or mV of the solution is displayed on LCD. Wait till the display on LCD is stabilized.

4.2.1.8    Note down the reading and press “RESET” key to put the instrument in stand by mode.

4.2.1.9    Clean the electrode with a suitable solvent, and then with distilled water and keep in pH 4.00 buffer / distilled water.

4.3    Calibration :

4.3.1    Switch on the pH meter and select operation mode as described in 4.1.

4.3.2    Ensure that tempreture correction is there by pressing  FWD/TEMPCO Key.

For this  press the FWD/TEMPCO  key and two option  ATC at : 1> 25 oC 2> 20 oC will be display on LCD, select 25 oC   by pressing  option 1.

4.3.3    Calibrate the instrument as follows (5 Pt. Cal.)

4.3.4    Press the mode key and pH mode will be display on screen

4.3.5    Then press enter . 

4.3.6    Now press “CAL” KEY “ to display previous calibration “Slope and Offset” will be display on  LCD. If previously calibrated the instrument otherwise “NO DATA” will be display on LCD.

4.3.7    Now press  the “ENTER KEY”  , display “ENTER PASSWORD” on LCD.

4.3.8    Enter the password “1234”, after entering the password   “Enter Buf 1=” will be displayed on LCD.

4.3.9    Keep the standard buffer solution 1.68  and  press the enter key .

4.3.10    Wait for stabilization of  pH and tempreture and press “Enter key” .

4.3.11    Now place  the Buffer  Solution 4.00,7.00,9.00 and 12.45 and  follows the point 4.4.13 and 4.4.14..

4.3.12    After calibration check Slope by pressing “ SCAN” key and check all 5 pH  buffer solution and record 

4.3.13    Slope should be more than 95.0% and offset value should not be more than ±30 mv.

4.4    Precautions :

4.4.1    Do not allow the electrodes to dry, it should always be dipped in pH 4.00 buffer / distilled water.

4.4.2    Do not wipe the glass electrode with any hard material or apply force. Use only tissue / filter paper for wiping.

4.4.3    Replace the saturated KCl solution in the electrode once in a month and place the electrode in 0.1 M HCl solution for 24 hrs. for activation.

4.4.4    Do not reuse buffer solutions after calibration.

4.4.5    Never use deionised water for the storage of electrode.

4.4.6    Wash the probe with suitable solvent thoroughly after use. Finally wash with distilled water.

Kcl solution, hcl solution, ph meter, microbiology