This video will show you how to perform a pH measurement.
Here are the equipment you will need.
There are two types of pH meters available in the lab:
Both of these meters can attach pH probes with automatic temperature control (ATC) function.
The standard buffer solutions, specifically pH 4.00, 7.00 and 10.00, are used to calibrate your pH meter every time before use.
To begin, turn on the VWR pH meter by pressing the right bottom button.
This particular VWR pH meter is connected to a Gel-filled pH probe with automatic temperature control function.
To clear the stored calibration, press Cal, and then CLEAR twice.
Remove the pH probe from the storage bottle carefully,
rinse with ddwater and gently dry with kimwipes.
You should always rinse the probe with ddwater between solutions.
Calibrate the pH probe by first immersing the pH probe in the pH 4 standard buffer.
Be sure to secure the pH probe upright on a clamp stand.
Press READ to begin calibration.
Wait until the value stabilizes.
This will be indicated by the auto read signal.
The eye will blink while stabilizing but will be still when the value has stabilized.
Rinse the pH probe with ddwater and dry with kimwipes.
Continue the calibration with standard buffers pH 7.00 and pH 10.00.
After calibration is complete, a slope will show up.
As long as it is within the range of 90% to 110%,
it will indicate a good electrode.
Press CAL to quit calibration and the pH meter is ready for use.
During the pH determination, you should make sure your sample is constantly stirred with a stir bar on a stir plate.
Keep the pH probe upright on the clamp stand and lower into the sample.
Make sure the pH probe never touches the stir bar or the probe will be damaged.
Press READ to read the pH, and record the pH when the eye stops blinking.
Rinse the pH probe and repeat the pH reading two additional times to obtain triplicate data.
When pH measurement is complete, rinse the pH probe with ddwater,
dry gently with kimwipes and store the probe in pH 4 buffer.
The Accumet AB15 pH meter is connected to an electrolyte-filled electrode.
Turn on the pH meter by pressing STANDBY.
Press SETUP twice to access the current calibration memory,
then press ENTER to clear the memory.
Next, press SETUP until you find the pH buffer group 2,4,7,10,12 and press ENTER to select this group.
To turn the probe to ON position, turn the purple ring on the probe until you can see an opening before use
This step is very important for accurate pH measurement.
Remove the pH probe from the storage bottle carefully,
rinse with ddwater and gently dry with kimwipes.
Calibrate the pH probe by first immersing the pH probe in the pH 4 standard buffer.
Be sure to secure the pH probe upright on the stand.
Press “Std” the access calibration mode,
then wait until the reading shows “stable” and you can press “Std” to enter the result.
Please note that this meter does not have the auto-read function.
Rinse the pH probe with ddwater and dry with kimwipes.
You should always rinse the probe with ddwater between solutions.
Continue the calibration with standard buffers pH 7.00 and pH 10.00.
After calibration is complete, a slope will show up very briefly.
As long as it is within the range of 90% to 110%, it will indicate a good electrode.
The pH meter is now ready for use.
During the pH determination,
you should make sure your sample is constantly stirred with a stir bar on a stir plate.
Keep the pH probe upright on the stand and lower into the sample.
Make sure the pH probe never touches the stir bar or the probe will be damaged.
The pH meter will automatically begin reading the sample.
Record the pH when the value shows “stable”.
Rinse the pH probe and repeat the pH reading two additional times to obtain triplicate data.
When pH measurement is complete, rinse the pH probe with ddwater,
dry gently with kimwipes and store the probe in pH 4 buffer.
Remember to turn the probe to OFF position by turning the purple ring on the probe until you can no longer see an opening.
This is very important because if the probe is left in the ON position,
the electrolyte will evaporate over time and the probe will be damaged.
In some cases, the pH meter may be connected to a pH probe without the automatic temperature control function and the pH meter will display “NO ATC”
In this case, you will not be able to obtain accurate pH reading unless your sample is equilibrated at room temperature.
Otherwise, you will need to use a thermometer to measure the temperature of your sample,
then use a pH meter specific convertor chart to obtain an accurate pH reading.