Current advances on the photocatalytic degradation of fluoroquinolones: photoreaction mechanism and environmental application

Heterogeneous photocatalysis is one of the most studied and promising techniques for degradation of contaminants of emerging concern, especially pharmaceuticals, and it represents a potential application in wastewater treatment of recalcitrant pollutants, such as fluoroquinolones, which are almost not abated by standard WWTPs. Although photodegradation partially contributes to alleviate their accumulation into the aquatic systems, heterogeneous photocatalysis assures complete sequestration and mineralization of FQs and their photoproducts and offers many advantages with respect to the other advanced oxidation processes (AOPs). The present brief review summarizes the most recent studies regarding the development and application of novel photocatalytic materials to the removal of FQs from contaminated waters. The collected data are arranged relating the mechanistic aspects to specific catalysts' properties, such as adsorption capacity, easy recovery, and reusability, especially under actual conditions.[GRAPHICS]

Photochemistry of some non zwitterionic fluoroquinolones

Two non zwitterionic analogues of fluoroquinolone drugs, viz. 1-ethyl-7-piperidino-8-fluoroquinol-4- one-3-carboxylic acid and 1-ethyl-7-piperidino-6,8-difluoroquinol-4-one-3-carboxylic acids have been synthesized and their photochemistry has been investigated. Both compound undergo photoheterolysis of the C8 F bond generating a triplet cation that either inserts into the 1-alkyl chain or is trapped or reduced by external nucleophiles. The reaction is analogous to that observed with the corresponding (zwitterionic) 7-piperazino derivatives, but the quantum yield is ca five times lower. This supports the rationalization that in the latter case assistance to defluorination by the N+ H bond has a determining role

Photoarylation of Alkenes and Heteroaromatics by Dibromo-BINOLs in Aqueous Solution

The photochemistry of 6,6’-dibromo-BINOLs (BINOL=2,2’-dihydroxy-1,1’-binaphthyl) under mild conditions has been investigated in neat and aqueous acetonitrile through product distribution analysis and laser flash photolysis. Arylation and alkylation have been successfully achieved in the presence of allyltrimethylsilane, ethyl vinyl ether, pyrrole, pyridine, thiophene, benzene, and indole. Such a photoreactivity offers a metal and protecting group free synthetic protocol toward mono- and disubstituted 6-aryl/alkyl BINOLs, since the BINOL chirality is preserved in the photoactivation process

Photoarylation/Alkylation of Bromo-Naphthols

The photochemistry of 6-bromo-2-naphthols has been studied in acetonitrile, aqueous acetonitrile, and isopropyl alcohol in the absence and in the presence of triethylamine by product distribution analysis, laser flash photolysis (LFP), fluorescence, phosphorescence, electrochemical measurements, and DFT calculations. Hydrobromic acid loss in the presence of Et3N occurs from the triplet state of 6-bromo-2-naphthol, generating an electrophilic carbene intermediate, which has been successfully trapped by oxygen, allyltrimethylsilane, 2,3-dimethylbut-2-ene, pyrrole, acrylonitrile, 1,4-dimethoxybenzene, and also pyridine. The generation and the reactivity of a triplet carbene intermediate has been supported by LFP, with the detection of 2,6-naphthoquinone-O-oxide (530-650 nm) in the presence of O2. The electrophilic diradical character of the carbene has been supported by DFT calculations, using the B3LYP, PBE0, and MPWB1K functionals, with the 6-31+G(d,p) basis set and PCM solvation model

Solid-Phase Extraction and HPLC determination of fluoroquinolones in surface waters

An investigation on filtration procedures and SPE sorbents used for the determination of traces of the most common veterinary fluoroquinolones (FQs), marbofloxacin (MAR) and enrofloxacin (ENR) used as antibacterial agents in cattle and swine farms in the province of Pavia (Italy), was performed in natural waters. The composition and the sorbent used in the SPE strongly influence the correct recovery,both in terms of total and issolved FQs concentration. An accurate comparison among different filters and SPE sorbents showed that a full determination of analytes was possible on nylon filters followed by anionic (WAX) and hydrophilic–lipophilic balance (HLB) resins as SPE. Quantitative analysis was done by chromatography with fluorescence detection (HPLC-FD). Fluoroquinolones recovery was between 90 and 116% with RSD not greater than 10% (sample volume 250 mL). The developed method allowed to determine both dissolved and NOM-absorbed fractions of FQs, therefore a full determination of the analytes was possible. Limits of detection (LOD) and quantification (LOQ) were, respectively, 0.7 and 2.2 ng/L for ENR and 2 and 6 ng/L for MAR. The kinetics of degradation under solar light was explored

Environmental photochemistry of fluoroquinolones in soil and in aqueous soil suspensions under solar light

The photodegradation fate of widely used fluoroquinolone (FQ) drugs has been studied both at the water–soil interface and in soil at actual concentrations (500 ng g−1) under natural solar light. Both human and veterinary drugs have been examined, namely ciprofloxacin, danofloxacin, enrofloxacin, levofloxacin, marbofloxacin and moxifloxacin. After spiking and irradiation, samples were submitted to microwave-assisted extraction and analyzed by high-performance liquid chromatography coupled to fluorescence detection (HPLC–FD). FQs degradation was faster in aqueous soil suspension than in neat soil (but lower than in “clean” water). A number of byproducts were identified by HPLC electrospray ionization tandem mass spectrometry after a post-extraction cleanup based on a molecularly imprinted polymer phase, for a more accurate detection. The distribution in the suspension was intermediate between those observed in soils and in aqueous solutions

Analytical Determination and Electrochemical Characterization ofthe Oxazolidinone Antibiotic Linezolid

Linezolid belongs to a class of antibiotics known as oxazolidinones. It is receiving great attention due to its activity toward multidrugs resistant bacteria, and simple and cheap methods for the analysis of this compound in pharmaceutical preparations are required. In this work, the electrochemistry of the antibiotic linezolid was investigated and a differential pulse voltammetric method based on the oxidation of the oxazolidinonic compound at a glassy carbon electrode has been developed and optimized for its determination; LOD of 50 mgL1 and a linearity up to 200 mgL1 were reported. The electrochemical process was studied by using different electrochemical techniques and confirmed by HPLC-MS/MS