The values of non-NIST (National Institute of Standards and Technology) pH standard buffers can vary unpredictably with temperature. This introduces an unknown calibration/test factor, which can undermine result consistency.

Hach pH standard buffers are developed to strict NIST guidelines, with pH temperature profiles well-characterized and fully documented. Hach HQd and sensION+ pH meters are programmed to recognize NIST and IUPAC (International Union of Pure and Applied Chemistry) certified pH standard buffers, and automatically adjust to provide true values over a wide range of temperatures.