Which type of buffer is recommended when calibrating a pH meter?

The choice of using a buffer with a pH close to the water's pH for calibrating a pH meter is significant for ensuring accurate measurements. When a pH meter is calibrated, it's crucial to align its readings closely with the specific conditions in which it will be used. Using a buffer that is compatible with the expected range of the sample pH helps the meter to adjust its readings accurately.

Calibrating at a pH close to the water's pH minimizes the potential for error. It allows the pH meter to create a more precise calibration curve, ensuring that readings taken subsequently will reflect true changes rather than inaccuracies introduced by a less-related calibration buffer. This is especially important in water quality testing, where small pH changes can indicate significant environmental shifts.

Selecting a buffer at pH 7 is useful in some cases, particularly for basic measurements, but it may not be ideal if the water sample has a different expected pH value. Similarly, buffers at pH 4-5 are better suited for acidic conditions, and distilled water does not provide a pH standard for calibration. Thus, using a buffer reflecting the anticipated pH range of the sample leads to improved accuracy and reliability in measurement results.