Enantiomeric analysis of polycyclic musks AHTN and HHCB and HHCB-lactone in sewage sludge by gas chromatography/tandem mass spectrometry.

Abstract

Enantioselective analysis of chiral compounds is an interesting and challenging technique used to elucidate the degradation/transformation mechanisms of these compounds or understand their environmental processes. In this study, we have developed an effective separation and detection approach for the enantiomeric analysis of AHTN and HHCB, as well as a transformation product of HHCB (HHCB-lactone), in sludge samples. The analytical method was developed using a cyclodextrin-based enantioselective gas chromatography column combined with tandem mass spectrometry (GC/MS/MS). The GC oven temperature gradients, the linear velocity of the helium carrier gas, as well as the MS/MS parameters, including quantitative and qualitative ion pairs, dwell times, and collision energies, were optimized to achieve good separation and high sensitivity for all target enantiomers. Baseline separations of all target enantiomers were observed. Limits of quantification (LOQs) for all enantiomers ranged from 0.010 to 0.045 μg/L, and calibration linearity for all single enantiomers was higher than 0.99. The intra-day and inter-day precisions for all single enantiomers of AHTN, HHCB, and HHCB-lactone ranged from 0.8 to 3.8% and from 4.2 to 8.3%, respectively. The developed method was fully validated through enantioselective analyses of AHTN, HHCB, and HHCB-lactone in sludge samples collected from 17 WWTPs. The enantiomeric fractions (EFs) of HHCB and HHCB-lactone in sludge samples distinctly deviated from 0.50, indicating a significant enantioselective transformation of HHCB with preferential degradation of the 4S enantiomers. Significant positive correlations were found between the EF values of cis-HHCB enantiomers and cis-HHCB-lactone enantiomers in the sludge samples, implying that further efforts are still needed to clarify the degradation/transformation mechanism from HHCB to HHCB-lactone.