Light-Induced Reactions of Chlorpromazine in the Presence of a Heterogeneous Photocatalyst: Formation of a Long-Lasting Sulfoxide

Abstract

A commercial carbon-modified titanium dioxide, KRONOClean 7000, was applied as a UV(A) and visible-light active photocatalyst to investigate the conversion of the antipsychotic pharmaceutical chlorpromazine in aqueous phase employing two monochromatic light sources emitting at wavelengths of 365 and 455 nm. Photocatalytic and photolytic conversion of chlorpromazine under both anaerobic and aerobic conditions was analyzed using a HPLC-MS technique. Depending on the irradiation wavelength and presence of oxygen, varying conversion rates and intermediates revealing different reaction pathways were observed. Upon visible light irradiation under aerobic conditions, chlorpromazine was only converted in the presence of the photocatalyst. No photocatalytic conversion of this compound under anaerobic conditions upon visible light irradiation was observed. Upon UV(A) irradiation, chlorpromazine was successfully converted into its metabolites in both presence and absence of the photocatalyst. Most importantly, chlorpromazine sulfoxide, a very persistent metabolite of chlorpromazine, was produced throughout the photolytic and photocatalytic conversions of chlorpromazine under aerobic conditions. Chlorpromazine sulfoxide was found to be highly stable under visible light irradiation even in the presence of the photocatalyst. Heterogeneous photocatalysis under UV(A) irradiation resulted in a slow decrease of the sulfoxide concentration, however, the required irradiation time for its complete removal was found to be much longer compared to the removal of chlorpromazine at the same initial concentration.

Regarding the Nature of Charge Carriers Formed by UV or Visible Light Excitation of Carbon-Modified Titanium Dioxide

“…Interestingly, the oxidation product of the chlorpromazine degradation, namely chlorpromazine sulfoxide, was found to be highly persistent throughout the visible light irradiation of K-7000 ( Figure S5). This product was found to be a long-lasting compound upon visible light driven photocatalysis as well, as previously reported [36]. This result can be understood on the same grounds as for methanol and chlorpromazine.…”

“…Thus, both the continuous irradiation experiments and the transient absorption spectroscopy measurements evince a prompt degradation of chlorpromazine and a negligible one for methanol. We note that chlorpromazine oxidation under UV irradiation of K-7000 has been the subject of a recent study [36] and, thus, we focused here on its visible light degradation.…”

Efficiencies Evaluation of Photocatalytic Paints Under Indoor and Outdoor Air Conditions

“…The photocatalytic anatase TiO 2 powders were (i) KRONOClean 7050 undoped TiO 2 (TiO 2 -Und), which has a specific surface area (S BET ) of 341 m 2 /g (Patzsch and Bloh, 2018) and an average particle size (APS) of 15 nm, and (ii) KRONOClean 7000 carbon-doped TiO 2 (TiO 2 -C) that presents an S BET of 251 m 2 /g and APS of 15 nm. The KRONOClean 7000 was thoroughly characterized by Arimi et al (2019) and Tobaldi et al (2015). The carbon doping was carried out through an aromatic carbon-based sensitizer layer on the photocatalyst (Arimi et al, 2019).…”

“…The KRONOClean 7000 was thoroughly characterized by Arimi et al (2019) and Tobaldi et al (2015). The carbon doping was carried out through an aromatic carbon-based sensitizer layer on the photocatalyst (Arimi et al, 2019). The KRONOClean 7050 powder is a pristine TiO 2 , being in this work a reference catalyst for the carbon-doped TiO 2 performance.…”

“…Nevertheless, the efficiency of paint 18TiO 2 -Und under visible illumination is significantly lower than the 18TiO 2 -C one. This is due to the fact that a visible-light carbonaceous sensitizer is present in the TiO 2 -C photocatalyst (Arimi et al, 2019). On the other hand, as the percentage of carbon-doped TiO 2 in the paint formulation decreases, both the UV, and the visible light efficiencies decrease.…”