Investigation of the photodegradation profile of tamoxifen using spectroscopic and chromatographic analysis and multivariate curve resolution

Photodegradation of tamoxifen (TAM) is investigated by chemometric analysis of the multiset data obtained by LC-DAD/MS and UV spectrophotometry. A hydroalcoholic solution of TAM was submitted to photodegradation by means of a dedicate irradiation cabinet able to simulate natural irradiation sources. The irradiance conditions were stressed by increasing the irradiation power to produce a rapid photodegradation of TAM. Drug photodegradation was monitored through UV spectrophotometry and the obtained photoproducts were investigated in detail by DAD/MS liquid chromatography. Data collected from the combination of both instrumental techniques were fused and processed jointly using the Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) method. A total number of five compounds were identified during the drug photodegradation and their kinetic evolution was described. The process included the isomerization of TAM to its (E)-form and the subsequent cyclization of these both compounds to give two phenanthrene derivatives. A photooxygenation process can also occur, giving a benzophenone derivative photoproduct as a result thereof. The multivariate resolution method proposed in this work allowed the resolution of this complex multicomponent system by the direct analysis of the experimental data.