Environmental fate processes and biochemical transformations of chiral emerging organic pollutants

Enantiospecific fate of ibuprofen, ketoprofen and naproxen in a laboratory-scale membrane bioreactor

The enantiospecific fate of three common pharmaceuticals was monitored in a laboratory-scale membrane bioreactor (MBR). The MBR was operated with a hydraulic retention time of 24 h and a mixed liquor suspended solids concentration of 8.6-10 g/L. Standard solutions of ibuprofen, ketoprofen and naproxen were dosed into the synthetic feed of the MBR. Influent and permeate samples were then collected for enantiospecific analysis. The individual (R)- and (S)-enantiomers of the three pharmaceuticals were derivatised using a chiral derivatizing agent to form pairs of diastereomers, which could then be separated and analysed by gas chromatography-tandem mass spectrometry (GC-MS/MS). Accurate quantitation of individual enantiomers was undertaken by an isotope dilution process. By comparing the total concentration (as the sum of the two enantiomers) in the MBR influent and permeate, ibuprofen, ketoprofen and naproxen concentrations were observed to have been reduced as much as 99%, 43% and 68%, respectively. Furthermore, evidence of enantioselective biodegradation was observed for all three pharmaceuticals. (S)-Ibuprofen was shown to be preferentially degraded compared to (R)-ibuprofen with an average decrease in enantiomeric fraction (EF) from 0.52 to 0.39. In contrast, (R)-ketoprofen was preferentially degraded compared to (S)-ketoprofen with a relatively minor increase in EF from 0.52 to 0.63. The use of a relatively pure enantiomeric solution of (S)-naproxen resulted in a significant change in EF from 0.99 to 0.65. However, this experiment consistently revealed significantly increased concentrations of (R)-naproxen during MBR treatment. It is hypothesised that the source of this (R)-naproxen was the enantiomeric inversion of (S)-naproxen. Such enantiomeric inversion of chiral pharmaceuticals during wastewater treatment processes has not previously been reported.

Discriminating multiple impacts of biogas residues amendment in selectively decontaminating chloroacetanilide herbicides

There is increasing concern about modifications to pesticide persistence in soil from the application of organic wastes as fertilizers. This study was conducted to discriminate the multiple effects of biogas residues (BR) amendment, including soil nutrients, soil microbial activity and biodiversity, and adsorption and degradation of chloroacetanilide herbicides (acetochlor, metolachlor, and butachlor). Addition of BR to soil increased the release of organic materials (i.e., dissolved organic carbon, dissolved organic nitrogen, and active phosphorus). It not only stimulated soil microorganisms and caused changes to microorganism diversity but also increased herbicide adsorption. Such multiple effects led to selective decontamination of chloroacetanilide herbicides, depending on herbicide structures and BR amendment levels. Stereoselectivity in degradation of acetochlor and metolachlor with biphasic character was magnified by BR amendment, which was well explained by integrating the impacts of BR amendment. Interestingly, BR amendment induced significant accumulation of herbicidally active aS,CS-metolachlor, facilitating the utilization of herbicidal activity.

Enantioselective degradation and unidirectional chiral inversion of 2-phenylbutyric acid, an intermediate from linear alkylbenzene, by Xanthobacter flavus PA1

Microbial degradation of the chiral 2-phenylbutyric acid (2-PBA), a metabolite of surfactant linear alkylbenzene sulfonates (LAS), was investigated using both racemic and enantiomer-pure compounds together with quantitative stereoselective analyses. A pure culture of bacteria, identified as Xanthobacter flavus strain PA1 isolated from the mangrove sediment of Hong Kong Mai Po Nature Reserve, was able to utilize the racemic 2-PBA as well as the single enantiomers as the sole source of carbon and energy. In the presence of the racemic compounds, X. flavus PA1 degraded both (R) and (S) forms of enantiomers to completion in a sequential manner in which the (S) enantiomer disappeared much faster than the (R) enantiomer. When the single pure enantiomer was supplied as the sole substrate, a unidirectional chiral inversion involving (S) enantiomer to (R) enantiomer was evident. No major difference was observed in the degradation intermediates with either of the individual enantiomers when used as the growth substrate. Two major degradation intermediates were detected and identified as 3-hydroxy-2-phenylbutanoic acid and 4-methyl-3-phenyloxetan-2-one, using a combination of liquid chromatography-mass spectrometry (LC-MS), and (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The biochemical degradation pathway follows an initial oxidation of the alkyl side chain before aromatic ring cleavage. This study reveals new evidence for enantiomeric inversion catalyzed by pure culture of environmental bacteria and emphasizes the significant differences between the two enantiomers in their environmental fates.

Enantioselective determination of triazole fungicide simeconazole in vegetables, fruits, and cereals using modified QuEChERS (quick, easy, cheap, effective, rugged and safe) coupled to gas chromatography/tandem mass spectrometry

A rapid and effective method for enantioselective determination of simeconazole enantiomers in food products (cucumber, tomato, apple, pear, wheat and rice) has been developed. The enantiomers were resolved by capillary gas chromatography (GC) using a commercial chiral column (BGB-172) and a temperature program from 150°C (held for 1 min) and then raised at 10°C min(-1) to 240°C (held for 10 min). This enantioselective gas chromatographic separation was combined with a clean-up/enrichment procedure based on the modification of QuEChERS (quick, easy, cheap, effective, rugged and safe) method. Co-extractives were removed with graphitized carbon black/primary secondary amine (GCB/PSA) solid-phase extraction (SPE) cartridges using acetonitrile:toluene (3:1, v/v) as eluent. Gas chromatography/ion trap mass spectrometry (GC-ITMS) with electron ionization (EI) was then used for qualitative and quantitative determination of the simeconazole enantiomers. Two precursor-to-product ion transitions (m/z 121-101 and 195-153) with the best signal intensity were chosen to build the multiple-reaction monitoring (MRM) acquisition method. The limits of detection for each enantiomer of simeconazole in six food products ranged between 0.4 and 0.9 μg kg(-1), which were much lower than maximum residue levels (MRLs) established by Japan. The methodology was successfully applied for the enantioselective analysis of simeconazole enantiomers in real samples, indicating its efficacy in investigating the environmental stereochemistry of simeconazole in food matrix.

Differential enantioselectivity of quizalofop ethyl and its acidic metabolite: direct enantiomeric separation and assessment of multiple toxicological endpoints

Transformation products usually differ in environmental and toxicological properties compared to the parent contaminants, thus causing potential and unknown environmental risks. To elucidate differential chiral recognition of the aryloxypropanoate herbicide quizalofop ethyl (QE) and its primary product (quizalofop acid, QA), their enantiomeric separation and toxicological impacts to two freshwater algae were investigated. Addition of trace water (0.02-0.08%, v/v) to the mobile phase selectively affected retention of analyte and induced simultaneous enantio-separation for the two compounds with intrinsical water-specific resolution mechanisms, although they both possessed a chiral center in the 2-position of propionates. In algal suspensions, QE was rapidly degraded to produce the acid metabolite (QA), and the product further declined, whereas a reduction of QA as starting compound did not occur. Uptake and/or transformation of QE and QA were found a lack of enantioselectivity and isomer inversion, while cellular membrane permeability, membrane potential and algal growth showed enantioselectivity to different extents. These results suggested the presence of receptor chirality that was involved in the toxicological processes but invalid for uptake and transformation. Therefore, quizalofop acid, identified as environmentally relevant contaminant associated with application of the herbicide, participated in the toxicological processes of the parent compound, and exhibited distinct toxicological and chromatographic retention properties.

Chiral separation of metalaxyl and benalaxyl fungicides by electrokinetic chromatography and determination of enantiomeric impurities

The enantiomers of two acylamine fungicides (metalaxyl and benalaxyl) were separated by EKC using CDs as chiral selectors. The use of 15 mM succinyl-γ-CD for metalaxyl and 5 mM succinyl-β-CD for benalaxyl dissolved in a 50 mM 2-morpholinoethanesulfonic acid buffer (pH 6.5), enabled the chiral separation of metalaxyl enantiomers in 11.5 min with a resolution of 3.1 and the enantiomeric separation of benalaxyl in 7.5 min with a resolution close to 15. Under these conditions, the two enantiomers of each of the chiral compound studied were also separated from folpet, very commonly present in fungicide formulations containing metalaxyl or benalaxyl. The analytical characteristics of the two developed methods were studied in terms of precision, linearity, selectivity, limits of detection (LODs) and limits of quantitation (LOQs) showing their suitability for the determination of these compounds in commercial agrochemical formulations. Finally, the development of an in-capillary preconcentration strategy allowed the detection of enantiomeric impurities up to 1.2% in commercial products labeled as enantiomerically pure in metalaxyl-M.

Enantiomeric fraction as an indicator of pharmaceutical biotransformation during wastewater treatment and in the environment--a review

Enantioselective analysis of some pharmaceuticals during wastewater treatment has the potential to reveal significant insights regarding the effectiveness of biotransformation processes. Furthermore, enantioselective analysis of chiral pharmaceuticals in the aquatic environment may provide a useful historical record revealing the dominant source of (treated or untreated) wastewater contamination. This review of the recent scientific literature has identified only a handful of studies that have directly investigated these promising applications. However, a range of enantioselective analytical techniques are likely to be adaptable from those which have been developed within the pharmaceutical industry. These include direct enantioseparations of enantiomers on chiral stationary phases as well as indirect separations by achiral stationary phases after chiral derivatization to form pairs of physically distinguishable diastereomers. Further investigations of the patterns of enantiomeric fractionation of pharmaceuticals in wastewater and environmental samples will provide an increasingly solid understanding of the relationship between biotransformation processes and the often overlooked parameter of enantiomeric fraction.

Pharmacologically active compounds in the environment and their chirality

Pharmacologically active compounds including both legally used pharmaceuticals and illicit drugs are potent environmental contaminants. Extensive research has been undertaken over the recent years to understand their environmental fate and toxicity. The one very important phenomenon that has been overlooked by environmental researchers studying the fate of pharmacologically active compounds in the environment is their chirality. Chiral drugs can exist in the form of enantiomers, which have similar physicochemical properties but differ in their biological properties such as distribution, metabolism and excretion, as these processes (due to stereospecific interactions of enantiomers with biological systems) usually favour one enantiomer over the other. Additionally, due to different pharmacological activity, enantiomers of chiral drugs can differ in toxicity. Furthermore, degradation of chiral drugs during wastewater treatment and in the environment can be stereoselective and can lead to chiral products of varied toxicity. The distribution of different enantiomers of the same chiral drug in the aquatic environment and biota can also be stereoselective. Biological processes can lead to stereoselective enrichment or depletion of the enantiomeric composition of chiral drugs. As a result the very same drug might reveal different activity and toxicity and this will depend on its origin and exposure to several factors governing its fate in the environment. In this critical review a discussion of the importance of chirality of pharmacologically active compounds in the environmental context is undertaken and suggestions for directions in further research are made. Several groups of chiral drugs of major environmental relevance are discussed and their pharmacological action and disposition in the body is also outlined as it is a key factor in developing a full understanding of their environmental occurrence, fate and toxicity. This review will be of interest to environmental scientists, especially those interested in issues associated with environmental contamination with pharmacologically active compounds and chiral pollutants. As the review will outline current state of knowledge on chiral drugs, it will be of value to anyone interested in the phenomenon of chirality, chiral drugs, their stereoselective disposition in the body and environmental fate (212 references).

Faster degradation of herbicidally-active enantiomer of imidazolinones in soils

Imidazolinones are chiral herbicides, comprised of two enantiomers with differential herbicidal activity. In this study, the selective degradation of enantiomers of the three imidazolinone herbicides, imazapyr, imazethapyr and imazaquin, was determined in a variety of soils selected to cover a broad range of physico-chemical characteristics. The R(+) enantiomer of all three herbicides, which has greater herbicidal activity (up to eight times), was found to degrade faster than the less active S(-) enantiomer. The enantiomer fraction (EF) was used as a descriptor of enantio-selectivity of the imidazolinone herbicides. The EF values increased with increasing incubation time for imidazolinones with a fast initial phase followed by a slower phase. While the enantio-selectivity was not significant in acidic soils (pH(w) 5.02 and 5.20), it was highly significant (P<0.001) in alkaline soils (pH(w) 7.6, 8.2 and 8.7). Significant positive correlations of EF values of imazapyr (P<0.001, R(2)=0.41), imazethapyr (P<0.002, R(2)=0.47) and imazaquin (P<0.001, R(2)=0.54) were found with the soil pH(w) ranging from 5.02 to 8.7. However, no correlation of EF was found with other soil properties. In addition to showing enantioselective degradation of the three herbicides in the soils studied, the study highlighted that for imidazolinones the herbicidally more active enantiomer can be preferably degraded by microorganisms.

Direct chiral resolution of metalaxyl and metabolite metalaxyl acid in aged mobile phases: the role of trace water

The separation of chiral transformation products greatly complements the understanding of the stereochemistry of chiral pollutants. In this study, direct enantiomeric resolution of metalaxyl and its main degradation product metalaxyl acid, often co-occurring in the environment, was carried out in normal-phase high-performance liquid chromatography with a Chiralcel OJ-H column. (R)-Metalaxyl acid and (S)-metalaxyl, which were almost parallel bonding to the chiral stationary phase, tended to separate, started to overlap, coeluted, and separated again with subtle changes of the mobile phase consisting of n-hexane, 2-propanol, acetic acid, and trace water. Their competition above hampered an acceptable direct separation in fresh mobile phases. Aged mobile phases with a storage period of 3-5 days, however, significantly improved their separation, in which trace water from moisture air diffusion was found to play a major role. Trace water differentially affected peak width and retention times and then induced enhanced peak separation, confirmed by deliberate addition of water to fresh mobile phases. Furthermore, none of the studied factors, involving temperature, concomitant analytes, and trace water, could cause changes of the configuration of the chiral stationary phase. Simultaneous enantiomeric separation of both compounds was achieved in aged or fresh mobile phases with adventitious or added water and gave satisfactory peak separation, all with Rs values of more than 1.20 in environmental samples.

Epimerization of cypermethrin stereoisomers in alcohols

Isomerization induced by light, heat, and organic solvents has been shown to occur for some pyrethroid insecticides. Alcohols are popular solvents that are used in sample extraction, storage, and analysis. Thus, alcohol-induced epimerization may contribute to the incorrect interpretation of results from enantioselective chemical analysis and bioassay of pyrethroids like cypermethrin. In this study, we investigated the relationship between the rate of epimerization of cypermethrin stereoisomers: 1R-cis-alphaR and 1R-trans-alphaR and short-chain alkyl alcohol properties. In this study, complete epimerization of 1R-cis-alphaR produced an almost equal fraction of 1R-cis-alphaS, and that of 1R-trans-alphaR yielded 1R-trans-alphaS. For both stereoisomers, epimerization was most rapid in ethanol. The same stereoisomers underwent relatively rapid epimerization in methanol, n-propanol, 2-methyl-1-propanol, and n-butanol but were stable in 2-butanol, suggesting that secondary alcohols have reduced reactivity, likely due to steric hindrance. We further evaluated epimerization of 1R-cis-alphaR and 1R-trans-alphaR stereoisomers of cypermethrin as a function of water content in methanol. The presence of water in methanol generally increased the epimerization rate. For 1R-cis-alphaR, epimerization was most rapid with a water content of < or =2%, while for 1R-trans-alphaR, epimerization was most rapid with a water content of 10%. Results from this study clearly show that contact with commonly used primary alcohols may result in rapid abiotic epimerization, underscoring the importance of considering configurational stability in ensuring the analytical integrity and correct interpretation of bioassay data for stereoisomers of cypermethrin and similar pyrethroids.

Influence of soil properties on the enantioselective dissipation of the herbicide lactofen in soils

A scheme was developed to elucidate the dissipation behaviors of the two enantiomers of the herbicide lactofen in soils using a normal-phase high-performance liquid chromatograph (HPLC) with UV detector and a column with a cellulose-tri-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). Eight soils with a wide range of soil properties were studied. Racemic and the enantiopure (S)-(+)- and (R)-(-)-lactofen were incubated under aerobic and anaerobic conditions. The data from sterilized controls indicated that the dissipation of lactofen was biological. The dissipation was shown to be enantioselective with (S)-(+)-enantiomer being degraded faster than the (R)-(-)-enantiomer, resulting in residues enriched with (R)-(-)-lactofen when the racemic compound was incubated. Lactofen was configurationally stable in soil, showing no interconversion of (S)-(+)- to (R)-(-)- enantiomer and vice versa. Significant correlations of the enantioselectivity, expressed as ES = (k((S)) - k((R)))/(k((S)) + k((R))) of lactofen with soil pH were observed under aerobic and anaerobic conditions. In addition, we found that the enantioselectivity correlated with the soil texture rather than the organic carbon.

Interindividual differences in o,p'-DDD enantiomer kinetics examined in Göttingen minipigs

Five minipigs were given a single oral dose of a racemic mixture of o,p'-DDD (30 mg kg(-1)b.w., EF=0.49). Blood plasma and subcutaneous adipose tissue were collected for analysis, at different time-points over 180 d. At the end of the experiment also liver, kidney and brain tissue were collected. Low concentrations of o,p'-DDD still remained after 180 d in plasma (mean 0.5+/-0.3 ng g(-1)f.w.) and in adipose tissue (mean 40+/-40 ng g(-1)f.w.). The mean concentrations in liver and kidney were 500+/-300 pg g(-1)f.w. and 90+/-50 pg g(-1)f.w., respectively. The enantiomers of o,p'-DDD were isolated by HPLC and the absolute configuration of the enantiomers were determined by X-ray crystallography and polarimetry as R-(+)-o,p'-DDD and S-(-)-o,p'-DDD. The enantiomer fractions (EFs) of o,p'-DDD were determined in plasma, adipose tissue and kidney using GC/ECD equipped with a chiral column. The EFs of o,p'-DDD in the individual minipigs showed large variability, ranging from 0.2 to 0.6 after 24h in plasma and from 0.2 to 0.7 after 90 d in adipose tissue. Hence in two of the minipigs, the S-(-)-o,p'-DDD enantiomer was dominating while the other enantiomer, R-(+)-o,p'-DDD was dominating in three minipigs. We propose that a yet not identified factor related to polymorphism, regulating the metabolism and/or elimination of the enantiomeric o,p'-DDD, is responsible for the differences in enantiomeric retention of the compound in the minipigs.

Chiral toxicology: it's the same thing...only different

Chiral substances possess a unique architecture such that, despite sharing identical molecular formulas, atom-to-atom linkages, and bonding distances, they cannot be superimposed. Thus, in the environment of living systems, where specific structure-activity relationships may be required for effect (e.g., enzymes, receptors, transporters, and DNA), the physiochemical and biochemical properties of racemic mixtures and individual stereoisomers can differ significantly. In drug development, enantiomeric selection to maximize clinical effects or mitigate drug toxicity has yielded both success and failure. Further complicating genetic polymorphisms in drug disposition, stereoselective metabolism of chiral compounds can additionally influence pharmacokinetics, pharmacodynamics, and toxicity. Optically pure pharmaceuticals may undergo racemization in vivo, negating single enantiomer benefits or inducing unexpected effects. Appropriate chiral antidotes must be selected for therapeutic benefit and to minimize adverse events. Enantiomers may possess different carcinogenicity and teratogenicity. Environmental toxicology provides several examples in which compound bioaccumulation, persistence, and toxicity show chiral dependence. In forensic toxicology, chiral analysis has been applied to illicit drug preparations and biological specimens, with the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse and "doping" screens. Adrenergic agonists and antagonist, nonsteroidal anti-inflammatory agents, SSRIs, opioids, warfarin, valproate, thalidomide, retinoic acid, N-acetylcysteine, carnitine, penicillamine, leucovorin, glucarpidase, pesticides, polychlorinated biphenyls, phenylethylamines, and additional compounds will be discussed to illustrate important concepts in "chiral toxicology."

Assessment of the pharmaceutical active compounds removal in wastewater treatment systems at enantiomeric level. Ibuprofen and naproxen

The enantioselective degradation of ibuprofen and naproxen enantiomers was evaluated in five different wastewater treatment systems, including three constructed wetlands (vertical- and horizontal-flow configurations), a sand filter and an activated sludge wastewater treatment plant. In addition, injection experiments were carried out with racemic ibuprofen at microcosm- and pilot-scale constructed wetlands. Ibuprofen and naproxen have an asymmetric carbon atom and, consequently, two enantiomeric forms (i.e. S and R). The enantiomeric fraction (EF=S/(S+R)) in the raw sewage and effluents of various wastewater treatments were found to be compound-dependent (i.e. ibuprofen: EF(influent)=0.73-0.90, EF(effluent)=0.60-0.76; naproxen: EF(influent)=0.88-0.90, EF(effluent)=0.71-0.86). Of the two chiral pharmaceuticals, naproxen was the only one whose effluent EF correlated with its removal efficiency (p<0.05). The lack of correlation found for ibuprofen was attributable to the fact that its enantioselective degradation kinetics were different under prevailing aerobic and anaerobic conditions. Injection experiments of ibuprofen in constructed wetlands at microcosm and pilot-scale followed similar trends. Hence, under prevailing aerobic conditions, S-ibuprofen degraded faster than R-ibuprofen, whereas under prevailing anaerobic conditions, the degradation was not enantioselective. In summary, the naproxen EF measurements in wastewater effluents show that naproxen is a suitable alternative for evaluating the removal efficiency of treatment systems because its enantioselective degradation is similar under prevailing aerobic and anaerobic conditions.

Enantioselective phytoeffects of chiral pesticides

Chirality exists extensively in nature. Synthetic chiral plant growth regulators and other pesticides usually behave enantioselectively in phyto-biochemical processes. Chiral plant growth regulators regulate the physiological processes of plants enantioselectively, and chiral pesticides cause enantioselective toxicities or ecotoxicities to plants. On the other hand, these chiral agrochemicals can be absorbed and enantioselectively metabolized by plants. This review summarizes the enantioselective effects of chiral plant growth regulators on plants and the phytotoxic and biotransformation effects of chiral herbicides and several persistent organic pollutants (POPs) on plants. Together, this information on the interactions between chiral agrochemicals and plants might shed light on studies on the chemical and biological behaviors of chiral chemicals, and direct research into the selection of plants, which can potentially decontaminate the environment.

JEM spotlight: recent advances in analysis of pharmaceuticals in the aquatic environment

Both ecosystem and human health rely on clean, abundant supplies of water, thus many classes of potential pollutants are regulated. In recent years, the possible risks associated with largely uncontrolled inputs of pharmaceuticals to rivers, lakes, groundwater, and coastal waters, mainly via wastewater, have been a focus of much research. During this time, our capacity to sequester, identify, and quantify pharmaceuticals in environmental matrices has improved. Devices have emerged to allow passive uptake of drugs to augment or replace laborious grab sampling. Advances in sample preparation have streamlined extraction procedures and removed interfering matrix components. New instrumental techniques have allowed faster, more accurate and sensitive detection of drugs in water samples. This review highlights all of these advances, from sample collection to instrumental analysis, which will continue to help us better understand the fate and effects of pharmaceuticals in aquatic systems.

Surface-to-food pesticide transfer as a function of moisture and fat content

Transfer of pesticides from household surfaces to foods may result in excess dietary exposure in children (i.e., beyond that inherent in foods due to agricultural application). In this study, transfer was evaluated as a function of the moisture and fat content of various foods. Surfaces chosen for investigation were those commonly found in homes and included Formica, ceramic tile, plastic, carpet, and upholstery fabric. Each surface type was sprayed with an aqueous emulsion of organophosphates, fipronil, and synthetic pyrethroids. In the first phase of the study, multiple foods (apples, watermelon, wheat crackers, graham crackers, white bread, flour tortillas, bologna, fat-free bologna, sugar cookies, ham, Fruit Roll-ups, pancakes, and processed American cheese) were categorized with respect to moisture and fat content. All were evaluated for potential removal of applied pesticides from a Formica surface. In the second phase of the study, representative foods from each classification were investigated for their potential for pesticide transfer with an additional four surfaces: ceramic tile, plastic, upholstery, and carpet. Moisture content, not fat, was found to be a determining factor in most transfers. For nearly all surfaces, more efficient transfer occurred with increased hardness (Formica and ceramic tile). Comparatively, the polymer composition of the plastic delivered overall lower transfer efficiencies, presumably due to an attraction between it and the organic pesticides of interest.

Stereoisomer analysis of wastewater-derived β-blockers, selective serotonin re-uptake inhibitors, and salbutamol by high-performance liquid chromatography–tandem mass spectrometry

A reversed-phase enantioselective liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) method was developed to measure enantiomer fractions (EF) and concentrations of pharmaceuticals in wastewater. Enantiomer resolution of six beta-blockers (atenolol, metoprolol, nadolol, pindolol, propranolol, and sotalol) along with two selective serotonin re-uptake inhibitors (citalopram, fluoxetine) and one beta(2)-agonist (salbutamol) was achieved with the Chirobiotic V stationary phase. Analyte recovery averaged 86% in influent and 78% in effluent with limits of detection ranging from 0.2 to 7.5 ng/L. These results represent an improvement in wastewater EF measurement for atenolol, metoprolol and propranolol as well as the first EF measurements of citalopram, fluoxetine, nadolol, pindolol, salbutamol and sotalol in wastewaters. Changes in EF through treatment indicate biologically mediated stereoselective processes were likely occurring during wastewater treatment.

Enantiospecific sublethal effects of the antidepressant fluoxetine to a model aquatic vertebrate and invertebrate

Many contaminants are chiral compounds with enantiomers that may differ markedly in environmental fate, bioavailability, and toxicity. Enantiospecific environmental fate and ecotoxicological information are lacking for many chiral contaminants. The primary objective of this investigation included an assessment of potential enantiospecific differences in sublethal standardized and behavioral responses of the model organisms Pimephales promelas (teleost) and Daphnia magna (crustacean) to the widely prescribed chiral antidepressant fluoxetine. Endpoints assessed included D. magna immobilization, reproduction, and grazing rate and P. promelas survival, growth, and feeding rate. S-Fluoxetine was found to be more toxic to sublethal standardized and behavioral endpoints in P. promelas, potentially because its primary active metabolite, S-norfluoxetine, is more potent than the same metabolite of R-fluoxetine in mammals. This was not observed for D. magna responses. This differential enantiospecific response between model organisms may have resulted from closer target homology between mammals and fish than between mammals and crustaceans. P. promelas feeding rate, an ecologically relevant and mode-of-action related response, was the most sensitive endpoint tested for R- and S-fluoxetine with 10% effect concentration (EC10) values (+/-SE) of 16.1 (+/-20.2) and 3.7 (+/-4.6) microg l(-1), respectively. Up to a 9.4-fold difference in toxicity between enantiomers was observed; P. promelas growth EC10s (+/-SE) for R- and S-fluoxetine were 132.9 (+/-21.2) and 14.1 (+/-8.1) microg l(-1), respectively. Such differences in sublethal responses to fluoxetine enantiomers suggest that enantiospecific toxicity and mode-of-action related responses that are ecologically relevant (e.g., feeding rate) should be considered in future ecological hazard and risk assessments for chiral contaminants.