Abstract
Ketamine (K) and its main metabolite, norketamine (NK), are chiral compounds that have been found in effluents from wastewater treatment plants (WWTPs) and aquatic environments. Little is known about their enantioselective biodegradation during sewage treatment; however, this information is pivotal for risk assessment, the evaluation of WWTP performance and wastewater epidemiological studies. The aim of this study was to investigate the biodegradation pattern of the enantiomers of K by activated sludge (AS) from a WWTP. For that, an enantioselective liquid chromatography with diode array detection (LC-DAD) method was developed and validated to quantify the enantiomers of K and NK. Both K and NK enantiomers were separated, in the same chromatographic run, using a Lux® 3 µm cellulose-4 analytical column under isocratic elution mode. The method was demonstrated to be linear (r2 > 0.99) and precise (<11.3%). Accuracy ranged between 85.9 and 113.6% and recovery ranged between 50.1 and 86.9%. The limit of quantification was 1.25 µg/mL for the enantiomers of NK and 2.5 µg/mL for K. The method was applied to monitor the biodegradation assay of the enantiomers of K by AS for 14 days. K was poorly biodegraded, less than 15% for both enantiomers, and enantioselectivity in the biodegradation was not observed. The metabolite NK and other possible degradation products were not detected. This work reports, for the first time, the behavior of both enantiomers of K in biodegradation studies.
Highlights
The Organization for Economic Co-operation and Development (OECD) recommends governments to take a collective, life cycle approach for managing pharmaceuticals in the environment
enantiomeric fraction (EF) these were not in both dark and light. These results are of high concern.inInthe fact, dataobserved are in accordance with other conditions. These results suggest that is photostable, and that the abiotic monitoring reports that have shown the occurrence of K in aquatic environments process seems not to contribute to the degradation of K during treatment
The biodegradation studies regarding the racemate of K in different conditions, with and without the addition of sodium acetate in dark and light conditions, showed that K is poorly degraded and photostable, which supports its persistence reported in the aquatic environment
Summary
The Organization for Economic Co-operation and Development (OECD) recommends governments to take a collective, life cycle approach for managing pharmaceuticals in the environment. The recommendations encourage the uptake of new monitoring methods to better understand and predict the risks and prioritize substances [1]. Enantioselective studies on biodegradation assays are important tools to investigate changes of the enantiomeric fraction (EF) during wastewater treatment and to predict the release of the enantiomers in aquatic ecosystems [2,3,4,5]. Enantioselective biodegradation has already been reported for some classes of pharmaceuticals such as beta-blockers, antidepressants and their metabolites, anticoagulants, non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics and illicit drugs [6,7,8,9,10].
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