Evaluation of Uncertainty in Determination Methods of Seawater pH Standard Material

Seawater pH standard material is determined by potentiometric methods with hydrogen electrode silver / silver chloride electrode in non-liquid junction cell. As a standard material, uncertainty is an important quality parameter. The sources of the uncertainty of determination methods mainly include measurement repeatability and temperature, atmospheric pressure, electrode potential, chloride concentration and so on. According to the experimental data, the expanded uncertainty of the method is 0.004. Finally, through in-depth analysis of the influence weight of each component, it is found that the quality control of the standard electrode potential, measurement repeatability and chloride ion concentration of the electrode in the ion system is the key to ensure the accuracy of the setting value, which provides a reliable guarantee for the replication of reference materials