By Philip J. Carlson, Updated Mar 24, 2022
A pH meter measures the potential difference created by a glass electrode that selectively allows hydrogen ions (H⁺) to pass through. The resulting voltage is compared against known reference points to determine the sample’s acidity or alkalinity.
Standard buffers are color‑coded solutions with certified pH values (e.g., 4.00, 7.00, 10.00). They are typically supplied by the meter manufacturer and provide the reliable reference points necessary for accurate calibration.
To construct a reliable calibration curve, at least three buffer standards are required. Without proper calibration, the meter cannot translate the measured voltage into a meaningful pH value, rendering results inaccurate or unusable.
All pH electrodes experience some drift over time due to changes in membrane sensitivity or electrode aging. Regular calibration against buffers corrects for this drift and keeps measurements trustworthy.
Using standardized buffers also mitigates issues arising from ionic strength differences or membrane fouling. This ensures that variations between samples do not compromise the accuracy of your pH readings.
