Photolytic and photocatalytic degradation of antineoplastic drug irinotecan. Kinetic study, identification of transformation products and toxicity evaluation

Abstract This study focused on the photolytic and photocatalytic degradation of the antineoplastic drug irinotecan (IRI) in aqueous solutions. Photocatalysis was carried out using commercial TiO2 (Degussa P25) and several operational parameters were studied. Identification and structure elucidation of TPs were carried out with the complementary use of SPE-LC-MS/MS and SPE-LC-TOF-MS. In order to separately study photodegradation and photocatalysis, different initial pH values were selected (7 and 4, respectively), where each process was dominant. Significant photolytic degradation of IRI was observed at neutral and basic pH. Kinetics of photodegradation followed the pseudo-first order model, with the maximum kobs observed at pH 7. Quantum yields of IRI for photolytic degradation were calculated using three different methods, ranging from 0.00022 to 0.00499 mol Einstein -1. Photocatalysis was the main phenomenon at pH 4 with the optimum concentration of TiO2 at 300 mgL -1, while different kobs ranged from 0.007 to 0.040 min -1.