Mechanism of UV photodegradation of fluoroquinolone antibiotic ciprofloxacin in aqueous solutions.

Mechanism of direct UV photolysis of the zwitterionic and anionic forms of the quinolone antibiotic ciprofloxacin (CIP) was revealed by combination of nanosecond laser flash photolysis, steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. For both forms, the main intermediate is a dissociative triplet state, which loses a fluorine ion to form a triplet carbocation; subsequent solvent attack of the latter leads to the formation of products of hydroxylation both the aromatic ring and the piperazyl substituent. Correspondingly, the quantum yield of photolysis of both CIP forms does not depend on the excitation wavelength, but depends on the concentration of dissolved oxygen.

Direct UV photodegradation of nalidixic acid in aqueous solutions: A mechanistic study.

Mechanism of direct UV photolysis of nalidixic acid (NA), a model quinolone antibiotic, was revealed using a combination of steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. Both quantum yields of photodegradation and detailed identification of final products were performed for the first time for two main forms of NA: neutral and anionic. The quantum yield of NA photodegradation is 0.

How to measure quantum yield of hydroxyl radical during photolysis of natural Fe(III) carboxylates?

The efficiency of oxidative species generation is one of the crucial parameters for the application of any system based on advanced oxidation processes (AOPs). This paper presents an approach to the correct determination of quantum yields of the hydroxyl radical upon UV photolysis of natural Fe(III) carboxylates, which are widely used in the works devoted to Environmental Chemistry and Water Treatment. The approach is based on the use of [FeOH] hydroxocomplex as a reference system with the well-known quantum yield of hydroxyl radical and benzene as a selective trap for the OH radical.

Iron (III) hydroxocomplex-methyl viologen dication system as a prospective tool for determination of hydroxyl radical reaction rate constants with environmental pollutants.

Reactivity of oxidative species with target pollutants is one of the crucial parameters for application of any system based on advanced oxidation processes (AOPs). This work presents new useful approach how to determine the hydroxyl radical reaction rate constants (k) using UVA laser flash photolysis technique. Fe (III) hydroxocomplex at pH 3 was applied as a standard source of hydroxyl radicals and methyl viologen dication (MV) was used as selective probe for OH radical.

Capillary zone electrophoresis as a simple approach for the study of p-arsanilic acid transformation in the process of photolytic degradation.

Arsenic aromatic compounds including p-arsanylic acid (pASA) are still widely used in a number of countries as the feed additives in animal breeding resulting in its entering the environment. Under the influence of oxidizing agents or UV radiation, pASA undergoes transformations leading to generation of inorganic arsenic species that are more mobile and toxic than organic ones. On the one hand, an approach based on the treatment of contaminated waters by UV irradiation seems perspective for their detoxification, but the feasibility of this approach depends on the composition of the products forming as a result of photodegradation.

Mechanistic investigation of humic substances assisted photodegradation of imipramine under simulated sunlight.

Imipramine (IMI) is a frequently prescribed tricyclic antidepressant and widely detected in the natural waters, while the environmental fate of IMI is yet poorly understood. Here, we investigated the photodegradation of IMI under simulated sunlight in the presence of humic substances (HS), typically including humic acid (HA) and fulvic acid (FA). The direct and indirect IMI photodegradation was found to increase both with increasing pH and with deoxygenation of the reaction solutions.

New insights into mechanism of direct UV photolysis of p-arsanilic acid.

The mechanism of direct UV photolysis of p-arsanilic acid (p-ASA), a widely used veterinary drug, was revised by means of laser flash photolysis coupled with high resolution liquid chromatography - mass spectrometry (LC-MS). None of p-ASA triplet state or singlet oxygen was found to directly participate in the photodegradation of p-ASA as it was assumed in previous works. Here we demonstrate that the main primary photoprocess is a monophotonic ionization (ϕ = 0.