Distinct enantiomeric signals of ibuprofen and naproxen in treated wastewater and sewer overflow.

Ibuprofen and naproxen are commonly used members of a class of pharmaceuticals known as 2-arylpropionic acids (2-APAs). Both are chiral chemicals and can exist as either of two (R)- and (S)-enantiomers. Enantioselective analyses of effluents from municipal wastewater treatment plants (WWTPs) and from untreated sewage overflow reveal distinctly different enantiomeric fractions for both pharmaceuticals. The (S)-enantiomers of both were dominant in untreated sewage overflow, but the relative proportions of the (R)-enantiomers were shown to be increased in WWTP effluents. (R)-naproxen was below method detection limits (<1 ng.L(-1)) in sewage overflow, but measurable at higher concentrations in WWTP effluents. Accordingly, enantiomeric fractions (EF) for naproxen were consistently 1.0 in sewage overflow, but ranged from 0.7–0.9 in WWTP effluents. Ibuprofen EF ranged from 0.6–0.8 in sewage overflow and receiving waters, and was 0.5 in two WWTP effluents. Strong evidence is provided to indicate that chiral inversion of (S)-2-APAs to produce (R)-2-APAs may occur during wastewater treatment processes. It is concluded that this characterization of the enantiomeric fractions for ibuprofen and naproxen in particular effluents could facilitate the distinction of treated and untreated sources of pharmaceutical contamination in surface waters.