Overview
This lecture explains how to properly use, calibrate, and maintain a stationary pH meter for accurate pH measurements.
Parts and Setup of a pH Meter
- A pH meter consists of the meter, an adjustable arm, and the electrode.
- The arm allows the electrode to be positioned into a sample easily.
- Remove the protective cap from the electrode before use.
- Electrodes must be stored capped and immersed in a storage solution to prevent drying.
Calibration Procedure
- Calibration should be done prior to each use for accurate results.
- Use standard color-coded buffer solutions with fixed pH values of 4, 7, and 10.
- Always rinse the electrode with distilled water between each calibration step.
- Start calibration with the pH 7 buffer, then rinse and repeat with pH 4, then pH 10.
- Calibration procedures may vary by meter; always consult the owner's manual.
Measuring pH of an Unknown Solution
- Place the unknown solution beneath the electrode and lower the arm to submerge the electrode.
- Wait for the meter to display the pH reading (example: pH 5.57 at 23.9°C).
- Remove the sample and rinse the electrode with distilled water after measuring.
- Replace the protective cap if finished with measurements.
Maintenance and Accuracy
- Calibrate the pH meter before each use to ensure measurement accuracy.
- Using three standards during calibration increases the reliability across a wide pH range.
- Proper cleaning and storage of the electrode prevents damage and ensures longevity.
Key Terms & Definitions
- pH Meter — device used to measure the acidity or alkalinity of a solution.
- Electrode — sensor part of the pH meter that detects pH.
- Buffer Solution — liquid with a known, fixed pH value used for calibration.
- Calibration — the process of adjusting the pH meter readings to known standards.
Action Items / Next Steps
- Read the owner’s manual for specific calibration procedures of your pH meter.
- Always store the electrode in its protective cap with storage solution when not in use.