The dye presents four characteristic bands, which agree with values found in the literature.25,26 The band at 254 nm is indicative of aromatic rings.27 A second band at 295 nm can be attributed to the structure of gamma acetylated acid,27 that is a precursor for the synthesis of RO16. The band 386 nm is probably related to the azo group. Finally, the band at 493 nm due to the chromophore7,27 is observed and used to monitor the removal of color