Optical Studies of the Spectral Properties of Phenothiazines

Abstract

Literature reports show numerous studies concerning the occurrence, evolution, detection and removal of, generically, pharmaceutical pollutants in/from environment. The current report is focused on the Phenothiazines class, in particular on Thioridazine (Thr). We discuss the time evolution of the absorption spectra of Thioridazine HCl solutions in ultra-pure water considering the racemic mixture and the two enantiomers: Thioridazine (-) and Thioridazine (+); the utilized concentration range was 10-5M-10-3M, and the temperature/light conditions were: 40C in dark, 220C in dark and 220C in daylight. The 10-5M Thr solutions were exposed at 266nm Nd:YAG pulsed laser radiation for time intervals between (1 - 3)h with the average pulse energy on the sample of 0.263mJ. Another irradiation experiment has involved Thr solutions at 5x10-2M, which were irradiated for time intervals between (1 – 30)min with 355nm Nd:YAG pulsed laser beam of average pulse energy on the sample 1.45mJ. The stability studies based on the absorption spectra measurements were conducted after exposure to the laser beams. The photodegradation processes of Thr are discussed. Keywords: Absorption spectra, Enantiomers, Nd:YAG laser, Phenothiazines, Photodegradation, Thioridazine, Pharmaceutical residues, half-lifetimes, cumulated drugs, spectroscopic properties, pharmaceutical pollutants, photochemical behaviour, Thioridazine (Thr), photoionization, IR spectral ranges, optical fibre