Distinct Enantiomeric Signals of Ibuprofen and Naproxen in Treated Wastewater and Sewer Overflow

Abstract

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.

A review on emerging contaminants in wastewaters and the environment: Current knowledge, understudied areas and recommendations for future monitoring

“…Nevertheless, available information in the literature show chiral ECs to be mostly non-racemic when present in surface waters (Table 3). Enantiomeric fractions range broadly from 0.1 for ibuprofen to 1.0 for naproxen and ephedrine (Kasprzyk-Hordern and Baker, 2012b; Khan et al, 2013) (an enantiomeric fraction of 0.5 denotes a racemic mixture). Concern arises from the large amount of toxicity testing being undertaken with racemic mixtures (or unknown/not reported enantiomeric composition) of the chemical under investigation ( Fig.…”

Chiral Analysis of Pesticides and Drugs of Environmental Concern: Biodegradation and Enantiomeric Fraction

“…Although it has been claimed that degrading microorganisms prefer the use of the (R)-enantiomer, as verified by Winkler et al [84], the majority of reports on enantioselective biodegradation of ibuprofen achieved disagreeing results, describing preferential degradation of (S)-ibuprofen. Accordingly, the influence of specific experimental settings (such as aerobic/anaerobic conditions) has been stated as preponderant in the enantioselective degradation of (S)-ibuprofen by other authors [83,94]. Naproxen presented enantioselective degradation profiles as well, with the EF decreasing under both aerobic and anaerobic conditions in WWTP treatments [83] and potential occurrence of enantiomeric inversion during a membrane bioreactor operation, where the (S)-form EF decreased over time and the (R)-form concentration increased [81].…”

Occurrence of Chiral Bioactive Compounds in the Aquatic Environment: A Review

“…Until the last decade, enantioselective studies for analysis of chiral compounds in the environment employed CD-based CSPs [61,85,[96][97][98][99] or indirect methods using enantiomerically-pure derivatizing reagents [9,60], which have been used until today [67,70,80,83,89]. Since 2010, a trend is being verified for the use of three types of CSPs: protein-based [68,69,[74][75][76][77]81,82,100,101], polysaccharide-based [54,55,78,79,102] and macrocyclic antibiotic-based CSPs [13,26,27,63,64,71-73, 76,78,88,91,103].…”

“…GC-MS/MS was employed in the first works reporting enantioselective environmental analysis by indirect methods using enantiomerically-pure derivatizing reagents [9,60], or by direct methods using CSPs [61,85]. Despite indirect [70,83] and direct methods [67,80,89] remaining in some studies, LC-MS/MS has been the analytical technique of election for illicit drugs and pharmaceutical while GC-MS and GC-ECD have been the most used for pesticides [13,54,55,57,62,[64][65][66][67][68][69][71][72][73][74][75][76][77][80][81][82]84,87,88,[90][91][92]95,[100][101][102][103][104][105]. Although much less used, LC-DAD, LC-UV and LC-FD detection have been used in some of the studies [11,26,27,…”

“…In that work, EF varied considerably between influents and effluents, mainly for ibuprofen and naproxen. Another study showed that the (S)-enantiomers of naproxen and ibuprofen were predominant in influent wastewaters, however EF decreased in WWTP effluents, suggesting that enantiomerization of profens may occur during processes occurring at WWTPs [89].…”