Study of the photodegradation of 2-bromophenol under UV and sunlight by spectroscopic, chromatographic and chemometric techniques

Abstract

This work is focused on the study of the photodegradation of 2-bromophenol under the action of UV light and sunlight. The photodegradation process has been monitored using UV–Vis spectroscopy and High Performance Liquid Chromatography coupled to diode array and mass spectrometry detectors in tandem (HPLC–DAD–MS). Multivariate resolution methods, such as Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) and hybrid soft- and hard-modeling-Multivariate Curve Resolution (HS-MCR), have been applied to the experimental data to obtain the information about the kinetic evolution and identification of the compounds involved in the photodegradation process. From the analysis of HPLC–DAD results, the complexity of the photodegradation process has been confirmed. Ten components were found to be involved in parallel, second- or higher-order reactions, which could not be ascertained from the spectroscopic results. The HPLC–MS results allowed postulating the identity of some of the compounds (such as hydroxyderivatives and bromophenol homologs) which resulted from the reactions of photohydrolysis, debromination and bromine transfer to different position of the phenol ring. The effect of the UV light and sunlight on the photodegradation process was found to affect mainly the rate of the reaction, but not the identity of the photoproducts formed. The advantages and limitations of the spectroscopic and chromatographic analysis were also discussed. The potential of combining spectroscopic and chromatographic data in a single multiset structure was also shown. This strategy, uses the advantage of the good definition of the process time axis from the spectroscopic experiment and the capability to distinguish among compounds, linked to the use of chromatographic information.