The Chinese full name of TOPS (CAS No. 40567-80-4) is N-ethyl-N - (3-sulfopropyl) -3-methylaniline sodium salt. It is a white to slightly brown powder belonging to the color reagent family. When used as a water-soluble reagent, it can be determined by enzymatic spectrophotometry for hydrogen peroxide. TOPS has been widely used due to its good water solubility, high sensitivity, and strong stability. The chromogenic substrate TOPS, also known as N-ethyl-N - (3-sulfopropyl) -3-methylaniline sodium salt, is similar to TOOS. Its molecular structure differs in that the sulfopropyl group on the single atom connected to the benzene ring is less than one hydroxyl group, with slightly stronger stability, high water solubility, and high detection sensitivity.