Radik, Melanie 1-2
How To Use the Iron Contaminated pH Machine
(Room 403)
1. Press “Power.”
a. May need to press twice.
2. Press “2nd” then “cal”
a. calibrate – in green
3. Calibrate for first pH reading:
a. If pHing on the acid side of the scale, open pH 4 calibration vial (pink).
b. If pHing on the basic side of the scale, open pH 7 calibration vial (yellow).
4. Rinse off the electrode into the Fe contaminated waste beaker with the squeeze
bottle of Milli-Q water.
5. Blot electrode end with Kim-wipe.
6. Place rinsed electrode in the calibration vial.
7. Wait for machine to “beep” and begin flashing calibrated value (4.01 or 7.00).
8. Press “yes.”
9. Rinse electrode. Blot.
10. Machine will automatically begin to calibrate the second value.
a. If pHing on the acid side of the scale, open pH 7 calibration vial (yellow).
b. If pHing on the basic side of the scale, open pH 10 calibration vial (blue).
11. Place electrode into second calibration vial.
12. Wait for machine to “beep” again and flash the calibrated value.
13. Press “yes.”
14. Machine will automatically switch from calibration mode to measure mode
a. “measure” will be in the upper right of the screen.
15. The screen will briefly display a % slope value.
a. If the value is less than 90.0% or more than 105% then the electrode is not
working properly.
b. See “Cleaning Instructions below”
16. Rinse electrode.
17. Place electrode in an iron-contaminated electrode holder-arm and lower into
solution.
18. Machine will “beep” when it has measured a stable pH value.
19. Once your solution is at the desired pH
20. Rinse electrode with Milli-Q
21. Blot electrode
22. Store electrode in pH 4 vial marked “Store Electrode Do Not Use To Calibrate.”
23. Machine will turn itself off automatically.
a. It may do so while you are measuring.
b. If so, merely press “power” until it turns on again and continue measuring.
c. No need to re-calibrate.
Cleaning Instructions:
If the % slope value is less than 90.0% or more than 105% then the electrode is not
working properly.
Radik, Melanie 2-2
Sometimes the electrode may have too much iron dried to it which prevents correct
measurements.
Try cleaning the electrode with the below directions.
1. Fill a 25 or 50mL graduated cylinder with 0.1N HCl solution
a. Dilute from the 0.5N HCl stock
b. Don’t forget to label it!
2. Turn off and unplug pH meter
3. Detach the electrode wire from the machine.
4. Place as much of the electrode as is dipped in media into the cylinder
a. About half-way up
b. DO NOT get the top of the electrode wet!
5. Allow it to soak for at least an hour but not more than three hours.
6. Rinse the electrode thoroughly with Milli-Q water.
7. Reattach the electrode to the machine and try re-calibrating.
8. If it still does not read a good slope, a new electrode will need to be purchased.