This standard is a national method for determining the sodium ion content in bisphenol A-type epoxy resins, with a particular focus on their aqueous extracts. The core of the method involves using a specific electrochemical detection instrument—a sodium ion concentration meter (or sodium ion depth meter)—to directly measure the pre-treated aqueous extract of the epoxy resin. To enhance the accuracy, efficiency, and applicability of the method to a broader range of resin types, the revised version of the standard (GB/T 12007.2-2025) also introduces another important analytical technique—flame atomic absorption spectroscopy. In modern laboratories, ion chromatography, as a highly sensitive instrument capable of simultaneously separating and detecting multiple ions, is also commonly applied in the analysis of impurity ions in epoxy resins, including sodium ions. This standard provides a fundamental quality control basis for evaluating the purity of epoxy resins, particularly their performance in high-end applications such as electronics.