Advancements in electrochemical technologies for the removal of fluoroquinolone antibiotics in wastewater: A review

In recent times, the need to make water safer and cleaner through the elimination of recalcitrant pharmaceutical residues has been the aim of many studies. Fluoroquinolone antibiotics such as ciprofloxacin, norfloxacin, enrofloxacin, and levofloxacin are among the commonly detected pharmaceuticals in wastewater. Since the presence of these pharmaceuticals in water bodies poses serious risks to living organisms, it is vital to adopt effective wastewater treatment techniques for their complete removal. Electrochemical technologies such as photoelectrocatalysis, electro-Fenton, electrocoagulation, and electrochemical oxidation have been established as techniques capable of the complete removal of organics including pharmaceuticals from wastewater. Hence, this review presents discussions on the recent progress (literature within 2018-2022) in the applications of common electrochemical processes for the degradation of fluoroquinolone antibiotics from wastewater. The fundamentals of these processes are highlighted while the results obtained using the processes are critically discussed. Furthermore, the inherent advantages and limitations of these processes in the mineralization of fluoroquinolone antibiotics are clearly emphasized. Additionally, appropriate recommendations are made toward improving electrochemical technologies for the complete removal of these pharmaceuticals with minimal energy consumption. Therefore, this review will serve as a bedrock for future researchers concerned with wastewater treatments to make informed decisions in the selection of suitable electrochemical techniques for the removal of pharmaceuticals from wastewater.

Assessing the presence of enrofloxacin and ciprofloxacin in piggery wastewater and their adsorption behaviour onto solid materials, with a newly developed chromatographic method

Veterinary antibiotics could enter the environment after the application of manure or farm wastewater on soil as fertilizer. In this study, a UPLC-MS/MS analytical method was developed and validated for the simultaneous determination of enrofloxacin (ENR) and ciprofloxacin (CIP) at environmental relevant concentrations in piggery wastewater, piggery wastewater solids, agricultural soil and ground water with good performance characteristics. The method recovery for ENR and CIP was 94.2 and 89.9% in the filtered piggery wastewater, 81.3 and 82% in the wastewater solid material, 78.1 and 76.8% in the soil and 95.6 and 97.3% in the ground water. The Limit of Detection (LOD) and Limit of Quantification (LOQ) for ENR were 21 and 64 ng L^-1 and for CIP was 18 and 54 ng L^-1, respectively. The method was implemented to monitor ENR and CIP in the wastewater of a piggery facility in Cyprus which applied anaerobic treatment before the final disposal of the reclaimed water. The highest antibiotic concentrations were measured in the wastewater samples collected from the nursery, where ENR is continuously used, with average concentration 31.4 μg L^-1 for ENR and 16.0 μg L^-1 for CIP. After the anaerobic digester, the two antibiotics were found only on the solid matter of the treated wastewater with an average concentration of 1.7 μg kg^-1 for ENR and 1.0 μg kg^-1 for CIP. The antibiotics adsorption at pH = 7 on clay soil, quartz sand and on solid matter isolated from the piggery wastewater was found to be higher than 95% for all solid materials. The concentration of the antibiotics in soil samples taken from a field where reclaimed piggery wastewater was applied for 10 years and in samples of groundwater from a nearby well was found for all samples below the LOD.

Development and validation of an HPLC confirmatory method for residue analysis of ten quinolones in tissues of various food-producing animals, according to the European Union Decision 2002/657/EC

The aim of this work was to develop an HPLC method for the simultaneous determination of ten quinolones: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, oxolinic acid, nalidixic acid, and flumequine, in various tissues of food-producing animals. Separation was achieved on a PerfectSil Target column (250 mm x 4 mm, ODS-3, 5 microm), by MZ-Analysentechnik (Germany), at room temperature. The mobile phase consisted of 0.1% TFA-CH(3)OH-CH(3)CN and was delivered by a gradient program of 35 min. The detection and quantitation was performed on a photodiode array detector at 275 and 255 nm. Caffeine (7.5 ng/microL) was used as the internal standard (IS). Analytes were isolated from tissue samples by 0.1% methanolic TFA solution. SPE, using LiChrolut RP-18 cartridges, was applied for further purification. The extraction protocol was optimized and the final recoveries varied between 92.0 and 107.4%. The method was fully validated according to Commission Decision 2002/657/EC. Limits of quantitation for the examined quinolones extracted from each tissue were much lower than the respective Maximum Residue Levels, ranging between 30 and 50 microg/kg for bovine tissue, between 30 and 55 microg/kg for ovine tissue, and between 40 and 50 microg/kg for porcine tissue.

Fluoroquinolone antibiotics in the environment

Fluoroquinolones (FQs) are used in large amounts for human and animal medical care. They are excreted as parent compound, as conjugates, or as oxidation, hydroxylation, dealkylation, or decarboxylation products of the parent compound. A considerable amount of FQs and their metabolites may reach the soil as constituents of urine, feces, or manure. The residues of FQs in foods of animal origin may pose hazards to consumers through emergence of drug-resistant bacteria. FQs bind strongly to topsoil, reducing the threat of surface water and groundwater contamination. The strong binding of FQs to soil and sediments delays their biodegradation and explains the recalcitrance of FQs. Wastewater treatment is an efficient elimination step (79%-87% removal) for FQs before they enter rivers. FQs are susceptible to photodegradation in aqueous medium, involving oxidation, dealkylation, and cleavage of the piperazine ring.

Determination of fluoroquinolones in edible animal tissue samples by high performance liquid chromatography after solid phase extraction

In the present work, a rapid, accurate, and sensitive method has been developed for the quantitative determination of five fluoroquinolones (enoxacin, ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin) in edible animal tissues (muscle tissue, liver, kidney, and eggs). The separation was accomplished on an Inertsil (250 x 4 mm) C8, 5 microm, analytical column, at ambient temperature within 15 min. The mobile phase consisted of a mixture of citric acid (0.4 mol L(-1))-CH3OH-CH3CN (87:9:4% v/v). UV detection at 275 nm yielded the following limits of detection: 100 pg per 20 microL injected volume for enoxacin, norfloxacin, and ciprofloxacin, 20 pg for ofloxacin, and 200 pg for enrofloxacin. Peaks in real samples were identified by means of a photodiode array detector. The method was validated in terms of intra-day (n = 8) and inter-day (n = 8) precision and accuracy. Tissue samples were purified from endogenous interference by solid-phase extraction using Oasis HLB cartridges. The solid-phase extraction protocol was optimized in terms of retention and elution. Recovery rates at fortification levels of 40, 60, and 80 ng/g ranged from 82.5% to 111.1%. The applicability of the method was examined using real samples from a chicken treated orally with the five studied fluoroquinolones.