FACULTY OF ENGINEERING

Department of Chemical and Environmental Engineering

 

Calibration Procedure

pH meter

 

Table of Content

 

1. Introduction    3

2. Scope    3

3. Health and safety    3

4. Personnel qualification    3

5. Method Calibration    3

6. Procedure and analysis    3

7. Data management    4

8. Quality control    4

9. Form    4

 

1. Introduction

The pH meter measures the pH of a solution using an ion-selective electrode (ISE) that responds to the H+ concentration of the solution. The pH electrode produces a voltage that is proportional to the concentration of the H+ concentration, and making measurements with a pH meter is therefore a form of potentiometry. The pH electrode is attached to control electronics which convert the voltage to a pH reading and displays it on a meter.

 

2. Scope

This protocol describes the method for the operation, two point calibration pH meter.

 

3. Health and safety

Personal protective equipment including safety glasses and lab coats should be used.

 

4. Personnel qualification

Personnel are required to be knowledgeable of this Calibration Procedure as well as the operation hints and maintenance sections of the pH meter instruction manual.

 

5. Method Calibration

As described in pH meter manual. General calibration method as describe in next section (procedure and analysis section).

 

6. Procedure and analysis

The pH meter is calibrated upon used or malfunctioning occurs on the pH meter display. The standard buffers used are pH 4.0, pH 7.0, and pH 10.0. A small amount is dispensed into a smaller container for calibration. Per manufacturers recommendations the standard pH buffers should be used for calibration only one time and disposed after calibration has been finalized.

 

Table 1: Fisher calibrated pH buffer was used for calibration

Fisher Catalogue Number

pH

Colour

SB101-500

4

Red

SB107-500

7

Yellow

SB115-500

10

Blue

 

 

6.1 Two Point Calibration

  • Check the level of the 3M KCl fill solution to ensure that it is within 25 mm of the filling hole. Bring to level if needed.
  • To calibrate, rinse the probe tip with de-ionized water, then place the tip of the electrode into the pH 7.0 buffer and press “Cal.”
  • The pH meter will automatically read the endpoint when the reading is stable. The appropriate buffer symbol will appear on the display. Record the pH value on the Calibration Record Form (see 9).
  • Rinse the tip of the electrode with de-ionized water.
  • Place the tip of the electrode in the second calibration buffer (either pH 4.0 buffer or pH 10.0 buffer) and press “Cal”.
  • The pH meter will automatically read the endpoint when the reading is stable and the appropriate buffer symbol will appear on the display.
  • The pH meter will also briefly display the electrode slope value. Record the pH value on the Calibration Record Form (see 9). If the slope is less than 95% or greater than 105%, refer to the troubleshooting section of the pH meter instructions manual or inform the supplier.
  • Rinse the electrode with de-ionized water. Confirm the calibration by reading the pH of the pH 7.0 buffer a second time. Record the pH value in the Calibration Record Form (see 9). Press “Mode” one time to switch to temperature mode. Record the temperature value in the Calibration Record Form (see 9). Press “Mode” two more times to return to pH mode.

 

7. Data management

Calibration data will be recorded promptly on the pH Meter Calibration Record form (see 9). Completed forms are archived in notebooks kept in secured file cabinets in the file room CA41. Only authorized personnel have access to the secured files

 

8. Quality control

The pH electrode is in good condition when the slope falls in arrange of 95% < Slope < 105%. For quality control purposes, the required information is documented on the appropriate forms (see 9).

 

9. Form    

pH Meter Calibration Record Form as per attachment.