The stereo-selective biodegradation of amphetamine and methamphetamine in river water using chiral-LC-QTOFMS

It is well known that the incomplete removal of pharmaceutcials and illicit drugs during sewage treatment results in their sustained emission to the aquatic environment. Less understood is that during sewage treatment and in the aquatic environment, chiral drugs can undergo stereospecific mechanisms controlling their fate. It has been reported that illicit drugs such as amphetamine and methamphetamine were observed in non-racemic proprotions following sewage treatment [1]. This evidence of stereo-selectivity in the aquatic environment represents a new challenge for the aquatic scientist. More than half of pharmaceuticals in use are chiral, of which 88% of these are administered in racemic proportions [2]. Considering this, current ecotoxicological data regarding racemic formulations needs to be reassessed. For example it has been observed that S-fluoxetine was more toxic to Pimephales promelas than R-fluoxetine [3]. This is compelling evidence that it is no longer sufficient to monitor racemic concentrations of common chiral drugs in the aquatic environment. Morever it has become clear that further research as to the stereo-specific fate of chiral pharmaceutcials and illicit drugs is necessary before predictions of ecotoxicity can be established.

This poster presents the stereo-specific biodegradation of amphetamine and methamphetamine in river water bioreactors in both light and dark conditions over a one-month duration. The aim of which was to determine whether the mechanisms governing the fate of amphetamine and methamphetamine was biological in natural. Bioreactor samples were analysed using a newly developed method utilising chiral-LC-(QTOF)MS [4]. Amphetamine was readily biodegraded in both light and dark conditions and demonstrated reduction in S+R concentration from 1000ng L-1 to <200 ng L-1 within five days. Methamphetamine was most persistent in the dark, demonstrating 33 – 47% biodegradation by day 29, whereas in the light, 93 – 98% biodegradation by day 29 was observed. Stereo-selectively was clearly observed, in both light and dark bioreactors, S-(+) amphetamine was preferentially eliminated within three days. With methamphetamine, stereo-selectively was also witnessed, however under light conditions, each bioreactor demonstrated biodegradation preference for different enantiomers. Thus indicating the potential complexity of stereo-selectivity within the aquatic environment.

References
[1] B. Kasprzyk-Hordern, D. Baker, Environ. Sci. Technol. 46 (2012) 1681.
[2] N. Lien Ai, H. Hua, P.H. Chuong, International Journal of Biomedical Science 2 (2006) 85.
[3] J.K. Stanley, A.J. Ramirez, C.K. Chambliss, B.W. Brooks, Chemosphere 69 (2007) 9.
[4] J.P. Bagnall, S.E. Evans, M.T. Wort, A.T. Lubben and B. Kasprzyk-Hordern, J. Chromatogr. A 1249 (2012) 115.