We present a proposal for evaluating and qualifying pH measuring devices based on the requirements of relevant standards. The proposal presented is based on ASTM E70, NBR 7353, JIS Z 8805, BS 3145, DIN 19268, NBR ISO 17025 and other standards, as well as the results of field research carried out in conjunction with professionals performing pH measurements in public health laboratories. Evaluation is performed by inspection of a form which records data from the measuring system. The form gives acceptable variations in the parameters being tested and allows a conclusion to be reached regarding acceptability of the system. Using the proposed protocol allows definition of suitable analysis criteria, while taking into account the influence pH measurement is subject and the need for correct results. This is particularly true when analyzing products already on the market, thus underlining the protocol's importance to the public health area.
Quality control; pH measurement; instrumentation