The primary pH meter validation and verification tests are:
1). Calibration
2). Accuracy
3). Precision
4). Linearity
5). Stability
1). Calibration
The pH meter must be calibrated before usage for reliable readings. Use standard buffer solutions with known pH values.
2). Accuracy
Comparing the pH meter’s values to a reference pH meter (or) verified reference material helps establish its accuracy.
3). Precision
Measure the pH of a sample numerous times and calculate the standard deviation to estimate the pH meter’s precision.
4). Linearity
The pH meter’s linearity can be determined by measuring solutions with different pH levels and plotting a calibration curve.
5). Stability
Measure the pH of a solution over time & track any changes to verify the pH meter’s stability.
Reference for pH meter Validation
ASTM E70-07 - Standard Test Method for the pH of the Aqueous Solutions With the Glass Electrode validates pH meters.