Coulometry is a primary method for measuring high purity substances. This is used to certify the primary reference materials required in a chemical analysis process. This paper describes the coulometric titration system developed by the National Metrology Institute (NMI) of Colombia for the certification of hydrochloric acid 0,1 mol·kg-1. In addition, it also shows preliminary studies for future development of and ethylenediaminetetraacetic acid disodium salt (EDTA-Na2) certification. The development of Coulometric method for purity certification of substances which have relevant importance for industries and academics in Colombia, provide metrology tools for ensuring traceability and quality of measurements in process of control and production apply to sectors such health, water and waste treatment, agriculture, food, chemical products, etc.