Complexing agents such as EDTA are used in soaps and other detergents in order to remove unwanted metal ions and to lower water hardness. The EDTA content in soaps and detergents can be determined using potentiometric titration with copper sulfate as titrant and the Cu-ISE as electrode for indication and cupric sulfate as titrant. 
Click here to access Metrohm’s application according to ASTM D1767.