Using a pH Meter

1. pH Calibration

1. Turn the meter's power on by pressing the "power" button.
2. Attach the automatic temperature compensation (ATC) probe if it is available and/or is not with the electrode.
3. Check that the measurement mode is pH. If not, press the "MODE" button until "pH" mode appears on the LCD display.
4. Consult the quick reference guide at the bottom of the meter or nearby for help if needed.
5. Always use fresh, unused, unexpired pH buffers for calibration. Buffers should be at the same temperature as the testing solutions.
6. Rinse the pH electrode with distilled water and then with the buffer being used for calibration (i.e., pH 7.00).
7. Dip the pH electrode into a neutral pH buffer (i.e., pH 7.00). Stir the buffer with a magnetic bar (at a moderate rate for ~30 s) for best results.
8. Press the "CAL/MEAS" (calibration [or Standardization]/easurement) button to select the 'calibration (standardization)' function. Set the buffer pH value on the meter display to 7.00.
9. When the "reading" is stable, press the "ENTER" button to accept. The primary reading will flash briefly before the secondary display begins scrolling through the remaining available buffers.
10. Rinse the pH electrode with distilled water and then with the buffer to be used for next calibration (i.e., pH 4.01).
11. Dip the pH electrode into the next buffer of pH 4.01. The meter display should be locked on the buffer value.
12. When the "reading" is stable, press "ENTER" to accept. The primary reading will flash briefly, then display the percent efficiency (slope) before the secondary display begins scrolling through the remaining the available buffers.
13. Repeat steps 2.2-2.7 to calibrate the pH 10.01 buffer.
14. The meter will automatically return to measurement mode upon the successful completion of the 3-point calibration.
    Notes: (1) The standard buffers of pH 4.01 and 10.01 may be replaced with other appropriate buffers per the testing samples' pH range. (2) For a single (neutral)-, or 2-point calibration, press the "CAL/MEAS" button to return to the measurements after completion of the calibration. (3) Calibration with more than 3 points may be used for more precise measurements. (4) It is recommended to perform the calibration at the beginning of each day. For very precise work the pH meter should be calibrated before each measurement. (5) Manually adjust the pH values of the buffers if the temperature differs from the standard room temperature and no ATC probe is attached.

2. pH Measurements

1. Confirm that the meter is on the pH measurement mode.
2. Thoroughly rinse the pH electrode between measurements with distilled water to prevent carryover contamination of the tested solutions. Gently blot the electrode on a laboratory cleaning tissue to remove the excess rinse water. Do not rub the bulb since this can cause a static charge buildup. Alternatively, rinse the electrode with the testing solution.
3. Dip the pH electrode into a testing solution or suspension. Stir the solution with a magnetic bar (~30 s) with the same stirring rate as for calibration for best results.
4. The pH is completed when the pH reading is stable.
5. If needed and available, press the "HOLD" button to freeze the measured reading. Press again to resume live reading.
6. Record the pH value (and temperature if needed) by writing down or pressing the "MEMORY" button (if applicable) to store the value into memory.
7. Repeat steps 3.2-3.6 for multiple measurements.
8. Thoroughly rinse and store the electrode in storage solution once all measurements are completed.
   Notes: (1) The pH probe response time in each buffer should be no longer than 60 s, but may be longer for some testing solutions/slurries. (2) The electrode probe should be cleaned using pH-electrode cleaning solution once a month, or whenever it is dirty. A 0.1 M HCl solution can be used for general cleaning. Diluted liquid detergent and household laundry bleach may be used for cleaning grease and bacterial contaminations. However, to avoid unexpected problems, the best practice is to always refer to the electrode manufacturer recommendations. (3) The pH electrode bulb should be moist at all times. Keep it in the electrode storage solution that comes with the electrode. Use pH 4 buffer solution if no storage solution is available. Use pH 7 buffer solution for a short time if neither are available.