Enantiomeric fractionation for quantitative assessment of anaerobic biodegradation rates: The case of climbazole.

International audienceAn efficient chiral liquid chromatography -high resolution - mas spectrometry method has been developed for thedetermination of climbazole (CBZ) enantiomers in wastewater / sludge.The obtimized analytical method has been validated with good qualityparameters including resolution > 1.1 and method quantification limitsdown to the ng/L range. On the basis of this newly developed analyticalmethod, the stereochemisttry of CBZ was investigated over time ineffluent / sludge biotic and steril microcosms under anaerobic dark andlight conditions and in influents and effluents of five differentsubsurface constructed wetlands (CWs). CBZ stereoselectivedegradation was exclusively observed under biotic conditions,confirming the specificity of enantiomeric fraction variations tobiodegradation processes. CBZ was always biotransformed into CBZalcohol due to the specific and enantioselective reduction of the ketonefunction into a secondary alcohol function. This transformation wasalmost quantitative and biodegradation gave a good first order kineticfit. We investigated the possibility to apply the Rayleigh equation toenantioselective processes by replacing the isotope ratio by theenantiomer ratio for quantitative biodegradation assessment of CBZ inbiological treatment processes and in receiving surface water or soil.The results of enantiomeric enrichment pointed the way for aquantitative assessment of in situ biodegradation processes due to agood fit (R2 > 0.98) of the anaerobic CBZ biodegradation to theRayleigh dependency in all the biotic microcosms and in CWs. Theseresults demonstrate that enantiomeric fractionation constitutes a veryinteresting quantitative indicator of CBZ biodegradation under anaerobicconditions. The enantiomeric fractionation tool does not imply toachieve a mass balance of the contaminant, which constitutes a relevantadvantage over the conservative tracer approaches. A prediction of theextent of biodegradation is also allowed as fars as the enantiomericenrichment factor is known