•Triarylmethane dyes (TAMs) undergo several degradation mechanisms.•Basic Blue 1 (BB1) shows significantly fast decolourization.•A new degradation mechanism for BB1 with photogenerated ·OH radicals is suggested.•Our mechanisms with other mechanisms can increase the possibility of TAM design.We studied triarylmethane dyes using LC/MS and UV/VIS spectrometry and demonstrated that they undergo several degradation mechanisms depending on their chemical structures, thus leading to specific degradation rates and colour fading. In particular, we found that Basic Blue 1 (BB1) shows significantly fast decolourization. We suggest a new specific degradation mechanism for BB1 that arises from photogenerated ·OH radicals from oxygen in air.

A stable tert-butyl(10-phenyl-9-anthryl)nitroxide (BPAN) radical was newly synthesized and used for the capture/characterization of reactive radicals. Adducts obtained from the reactions of BPAN with in situ generated reactive radicals showed excellent stability, assuring complete isolation and purification. The structures of the adducts were established by LC–MS and NMR analyses.