Environmental fate processes and biochemical transformations of chiral emerging organic pollutants

Bioaccumulation and biotransformation of 1,2-bis (2,4,6-tribromophenoxyethane) (BTBPE) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) in zebrafish (Danio rerio)

Despite the increasing production, use, and ubiquitous occurrence of novel brominated flame retardants (NBFRs), little information is available regarding their fate in aquatic organisms. In this study, the bioaccumulation and biotransformation of two typical NBFRs, i.e., 1,2-bis (2,4,6-tribromophenoxyethane) (BTBPE) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH), were investigated in tissues of zebrafish (Danio rerio) being administrated a dose of target chemicals through their diet. Linear accumulation was observed for both BTBPE and TBECH in the muscle, liver, gonads, and brain of zebrafish, and the elimination of BTBPE and TBECH in all tissues followed pseudo-first-order kinetics, with the fastest depuration rate occurring in the liver. BTBPE and TBECH showed low bioaccumulation potential in zebrafish, with biomagnification factors (BMFs) < 1 in all tissues. Individual tissues' function and lipid content are vital factors affecting the distribution of BTBPE and TBECH. Stereoselective accumulation of TBECH enantiomers was observed in zebrafish tissues, with first-eluting enantiomers, i.e. E1-α-TBECH and E1-β-TBECH, preferentially accumulated. Additionally, the transformation products (TPs) in the zebrafish liver were comprehensively screened and identified using high-resolution mass spectrometry. Twelve TPs of BTBPE and eight TPs of TBECH were identified: biotransformation pathways involving ether cleavage, debromination, hydroxylation, and methoxylation reactions for BTBPE and hydroxylation, debromination, and oxidation processes for TBECH. Biotransformation is also a vital factor affecting the bioaccumulation potential of these two NBFRs, and the environmental impacts of NBFR TPs should be further investigated in future studies. The findings of this study provide a scientific basis for an accurate assessment of the ecological and environmental risks of BTBPE and TBECH.

THz enantiomers of drugs recognized by the polarization enhancement of gold nanoparticles on an asymmetric metasurface

Chirality plays an important role in biological processes, and enantiomers often possess similar physical properties and different physiological functions. Thus, chiral detection of enantiomers has become a hot topic in recent years, and methods to enhance chiral molecular recognition are in urgent demand. In this work, a polarization detection method was used for different chiral drugs based on a specially designed metasurface composed of asymmetric double-opened rings and the surface enhancement effect of gold nanoparticles (GNPs). The experiment results show that the frequency shifts caused by the nearfield interaction of the metasurface and biomolecules have been significantly improved by GNPs, and both the limit of detection and detection precision of the metasurface can reach the 10-5 g ml-1 level. Moreover, the polarization sensing characterized by right circular polarization (RCP), the polarization elliptical angle (PEA), and the polarization rotation angle (PRA) shows that the enantiomers of three drugs can be distinguished, especially using the PEA spectrum; the maximum difference between enantiomers is over 30° with a precision of 6.6 × 10-7 g mL-1. Our THz polarization sensing and the GNP enhancement method inspire an efficient strategy for the highly sensitive detection of enantiomers.

Effect of HHCB and Cd on phytotoxicity, accumulation, subcellular distribution and stereoselectivity of chiral HHCB in soil-plant systems

The toxicity of HHCB in the growth and development of plants is well known, but its uptake, subcellular distribution, and stereoselectivity, especially in a co-contamination environment, is not fully understood. Therefore, a pot experiment was performed to research the physiochemical response, and the fate of HHCB in pakchoi when the Cd co-existed in soil. The Chl contents were significantly lower, and the oxidative stress was aggravated under the co-exposure of HHCB and Cd. The accumulations of HHCB in roots were inhibited, and those in leaves were elevated. The transfer factors of HHCB in HHCB-Cd treatment increased. The subcellular distributions were analyzed in the cell walls, cell organelles, and cell soluble constituents of roots and leaves. In roots, the distribution proportion of HHCB followed cell organelle > cell wall > cell soluble constituent. In leaves, the distribution proportion of HHCB was different from that in roots. And the co-existing Cd made the distribution proportion of HHCB change. In the absence of Cd, the (4R,7S)-HHCB and (4R,7R)-HHCB were preferentially enriched in roots and leaves, and the stereoselectivity of chiral HHCB was more significant in roots than leaves. The co-existing Cd reduced the stereoselectivity of HHCB in plants. Our findings suggested that the fate of HHCB was affected by the co-existing Cd, so the risk of HHCB in the complicated environment should be paid more attention.

The Enediolate Chemistry of Free Carboxylic Acids

The synthetic methodologies for the α-functionalization of free carboxylic acids through the enediolate intermediates are summarized in this review. In general, the enediolates could be generated in situ or transiently from free carboxylic acids with a stoichiometric or catalytic amount of protection reagents, including metal, boron, and silicon reagents. The in situ or transient generated enediolates were subsequently subjected to racemic or asymmetric reactions with various electrophiles, producing the α-functionalized free carboxylic acids in a single step. In addition, the enediolate could undergo an α-oxidation reaction with TEMPO through the radical process.

The dichloroacetamide safener benoxacor is enantioselectively metabolized by monkey liver microsomes and cytosol

The metabolism and toxicity of current-use herbicide safeners remain understudied. We investigated the enantioselective metabolism of the safener benoxacor in Rhesus monkey subcellular fractions. Benoxacor was incubated with liver microsomes and cytosol from female and male monkeys (≤30 min). Benoxacor levels and enantiomeric fractions were determined with gas chromatography. Benoxacor was metabolized by microsomal cytochrome P450 enzymes (CYPs), cytosolic glutathione-S-transferases (GSTs), and microsomal and cytosolic carboxylesterase (CESs). CES-mediated microsomal metabolism followed the order males > females, whereas the CYP-mediated clearance followed the order females > males. CYP-mediated metabolism initially resulted in an enrichment of the second eluting benoxacor enantiomer (E₂-benoxacor), whereas the first eluting benoxacor enantiomer (E₁-benoxacor) was enriched after 10 or 30 min in female or male microsomal incubations. Benoxacor metabolism by GSTs was enantiospecific, with a total depletion of E₁-benoxacor after approximately 20 min. Thus, the enantioselective metabolism of benoxacor by GSTs and CYPs may affect its toxicity.

Evaluating phospholipid- and protein-water partitioning of two groups of chemicals of emerging concern: Diastereo- and enantioselectivity

The partitioning between phospholipids/proteins and water can be used to predict the bioaccumulation potential of chemicals with better accuracy compared with n-octanol-water partition coefficient. However, such partitioning is poorly understood for chiral chemicals, many of which exhibit differential bioaccumulation and toxicity potential between enantiomers. In this study, the enantiospecific liposome-water and bovine serum albumin (BSA)-water partition coefficients (Klip/w and KBSA/w, determined at 25 ℃ and 37 ℃, respectively) were measured by equilibrium dialysis for α-, β-, and γ-hexabromocyclododecane (HBCD) and three β-blockers (propranolol, metoprolol, and sotalol). Raman and fluorescence analyses and molecular docking were conducted to provide additional insights into the partitioning process. Results showed α- and β-HBCD displayed stronger enantioselective partitioning to liposomes with the (-)-form, while (-)-α-HBCD, R-(+)-propranolol, R-(+)-metoprolol, and E2-sotalol favored partitioning to BSA compared with their antipodes. Raman spectra revealed α- and γ-HBCD enhanced and reduced the organization of liposome acyl chains, respectively, and polar interactions enhanced the liposome partitioning of β-blockers. Fluorescence spectra indicated the changed tryptophan microenvironment might influence the BSA steric effect toward HBCD, and electrostatic interactions dominated the formation of BSA-β-blocker complexes. Molecular docking results supported the difference in the thermodynamic nature of interaction between the studied enantiomers and BSA.

Enantiomer/stereoisomer-specific residues of metalaxyl, napropamide, triticonazole, and metconazole in agricultural soils across China

In this study, the residual status of four chiral pesticides including metalaxyl, napropamide, triticonazole, metconazole, and their enantiomers/stereoisomers were investigated in agricultural soils across China. The levels in the soils were detected as non-detected (n.d.)-16.67 ng/g for metalaxyl with a median of 0.14 ng/g; 0.004-32.99 ng/g for napropamide with a median of 0.29 ng/g; n.d.-207.39 ng/g for triticonazole with a median of 1.29 ng/g; and n.d.-71.83 ng/g for metconazole with a median of 1.03 ng/g, respectively. Enantiomer/stereoisomer-specific residues were observed for metalaxyl and triticonazole. R-Metalaxyl and R-triticonazole were identified as the major enantiomers in the soils for the two pesticides. There was no obvious enantioselective residue for napropamide in most of the soils. As for metconazole, metconazole-1 and metconazole-4 were identified as the major stereoisomers in the soils. These results suggest that enantiomer/stereoisomer-specific risk should be considered when assessing the ecological safety of these pesticides in soils.

On-line coupling of supercritical fluid extraction with enantioselective supercritical fluid chromatography-triple quadrupole mass spectrometry for the determination of chiral pesticides in hemp seeds: A proof-of-principle study

The present research can be considered as a proof-of-principle study focused on the determination of chiral pesticides using a supercritical fluid extraction instrument coupled on-line with an enantioselective supercritical fluid chromatography-triple quadrupole mass spectrometry. To the best of Authors' knowledge, this is the first description of an on-line approach for the extraction and determination of chiral pesticides. Metalaxyl, benalaxyl and dimethenamid were investigated in nine hemp seed samples belonging to four varieties of Cannabis sativa; only in one case a pesticide was found at levels above the method limit of quantification (LoQ), though within the EU maximum residue level value. The figures-of-merit determined were linearity, precision, limit of detection (LoD), and LoQ. Regression coefficients were between 0.9856 and 0.9973, the LoDs were in the 0.04-0.41 μg kg^-1 range, the LoQs were in the 0.12-1.38 μg kg^-1 range, while coefficients of variation were between 1 and 3% (10 μg kg^-1 level).

Polychlorinated biphenyls (PCBs) in the colostrum samples from the Yangtze River Region: Exposure profile and risk assessment

Polychlorinated biphenyls (PCBs) may transfer into the neonates through the placental transfer and via breastfeeding after the delivery, thus might be harmful to the infant. Sixty colostrum samples in the Yangtze River Region were collected to investigate the concentration, distribution pattern, and enantiomer characteristic of the PCB exposure. Among all samples, over 90% of pollutants were tetra-to hepta-chlorinated PCBs. The sum concentration of the PCB was 512 (IQR: 322-856) ng g^-1 lipid weight. Enantiomer fraction (EF) of PCB 95 and PCB 149 was found lower than the racemic value, while EFs of PCB 45 and PCB 136 were found higher and near-racemic state, respectively. The concentration pattern and enantiomeric properties of the PCBs indicated that the mothers from Mianyang had a recent exposure to PCBs. Among all samples, similar exposure and metabolic pathways of the PCB congeners were observed. PCB exposure showed no significant correlation with the birth outcome of the infants, but 43.3% of the infants have potential health risks via breastfeeding.

Absolute Configuration Sensing of Chiral Aryl- and Aryloxy-Propionic Acids by Biphenyl Chiroptical Probes

The absolute configuration of chiral 2-aryl and 2-aryloxy propionic acids, which are among the most common chiral environmental pollutants, has been readily and reliably established by either electronic circular dichroism spectroscopy or optical rotation measurements employing suitably designed 4,4′-disubstituted biphenyl probes. In fact, the 4,4′-biphenyl substitution gives rise to a red shift of the diagnostic electronic circular dichroism signal of the biphenyl A band employed for the configuration assignment, removing its overlap with other interfering dichroic bands and allowing its clear sign identification. The largest A band red shift, and thus the most reliable results, are obtained by employing as a probe the 4,4′-dinitro substituted biphenylazepine 3c. The method was applied to the absolute configuration assignment of 2-arylpropionic acids ibuprofen (1a), naproxen (1b), ketoprofen (1c) and flurbiprofen (1d), as well as to the 2-aryloxypropionic acids 2-phenoxypropionic acid (2a) and 2-naphthoxypropionic acid (2b). This approach, allowing us to reveal the sample’s absolute configuration by simple optical rotation measurements, is potentially applicable to online analyses of both the enantiomeric composition and absolute configuration of these chiral pollutants.

Metathetic approach to new NORPHOS-related bisphosphanes: facile synthesis and application in asymmetric hydrogenation

A highly efficient synthesis of new chiral bisphosphanes derived from the renowned NORPHOS ligand is presented. The synthesis involves ring-opening metathesis of NORPHOS dioxide with an external olefin, followed by saturation of the new double bonds and adjustment of the oxidation level of phosphorus centers oxidation level. The synthesized bisphosphanes retain the configuration and enantiomeric purity of the starting NORPHOS. Their utility as ligands in asymmetric catalysis is exemplified using an open-NORPHOS ligand in some benchmark Rh-catalyzed hydrogenations of enamides where excellent chemical yields and enantiomeric purities of the products have been secured. The proposed protocol demonstrated the possibility of a straightforward synthesis of new chiral catalysts to be utilized in the asymmetric synthesis of pharmaceutically important compounds, such as amino acid derivatives.

Biochemical and molecular responses of maize (Zea mays L.) to 1,2-dibromo-4-(1,2 dibromoethyl) cyclohexane (TBECH) diastereomers: Oxidative stress, DNA damage, antioxidant enzyme gene expression and diversity of root exudates

The phytotoxicities of TBECH diastereomers to plants at the biochemical and molecular levels were investigated in a hydroponic study by using maize as a model plant. The results showed that TBECH could induce the production of two species of reactive oxygen species (ROS), O₂^•- and H₂O₂, in maize tissues. The accumulation of ROS was the highest when maize was exposed to β-TBECH. TBECH enhanced the phosphorylation of plant histone, and the contents of γ-H2AX in maize followed the order β-TBECH > αβ-TBECH > γδ-TBECH > γ-TBECH. Transcriptome profiling revealed that antioxidant enzyme genes (AEGs) were over-expressed in maize when stressed by technical grade TBECH. The RT-PCR detection further validated that three typical AEGs, including CAT, SOD, and POD genes, were time-dependent and selectively expressed under the influence of TBECH diastereomers. Molecular compositions of maize root exudates characterized by FT-ICR-MS were significantly different among the four groups of TBECH diastereomer treatments. TBECH diastereomers specifically affected the chemical diversity and abundance of root exudates. New insights into the biochemical effects of TBECH on plants are provided in this work, which is helpful to deepening the understanding of their stereo-selectivity.

A review on the stereospecific fate and effects of chiral conazole fungicides

The production and use of chiral pesticides are triggered by the need for more complex molecules capable of effectively combating a greater spectrum of pests and crop diseases, while sustaining high production yields. Currently, chiral pesticides comprise about 30% of all pesticides in use; however, some pesticide groups such as conazole fungicides (CFs) consist almost exclusively of chiral compounds. CFs are produced and field-applied as racemic (1:1) mixtures of two enantiomers (one chiral center in the molecule) or four diastereoisomers, i.e., two pairs of enantiomers (two chiral centers in the molecule). Research on the stereoselective environmental behavior and effects of chiral pesticides such as CFs has become increasingly important within the fields of environmental chemistry and ecotoxicology. This is motivated by the fact that currently, the fate and effects of chiral pesticides such as CFs that arise due to their stereoselectivity are not fully understood and integrated into risk assessment and regulatory decisions. In order to fill this gap, a summary of the state-of-the-art literature related to the stereospecific fate and effects of CFs is needed. This will also benefit the agrochemistry industry as they enhance their understanding of the environmental implications of CFs which will aid future research and development of chiral products. This review provides a collection of >80 stereoselective studies for CFs related to chiral analytical methods, fungicidal activity, non-target toxicity, and behavior of this broadly used pesticide class in the soil environment. In addition, the review sheds more light on mechanisms behind stereoselectivity, considers possible agricultural and environmental implications, and suggests future directions for the safe use of chiral CFs and the reduction of their environmental footprint.

β-cyclodextrin improve the tolerant of freshwater algal Spiny Scenedesmus to chiral drugs venlafaxine and its metabolite

This study based on the freshwater algae Spiny scenedesmus (S. scenedesmus) with tolerance to venlafaxine aiming to investigate algae removal abilities. Here presented for the first time to evaluate the effect of β-cyclodextrin (β-CD) on reduce toxicity and enhance removal ability of venlafaxine and O-desmethylvenlafaxine to S. scenedesmus. Based on dose-response results, the toxicity of R-venlafaxine (EC₅₀ = 6.81 mg·L ^-1) and R-O-desmethylvenlafaxine (EC₅₀ = 3.36 mg·L ^-1) to algae were more than two times than those in the presence of β-CD treatment (10.64 mg L ^-1 for R-venlafaxine and 11.87 mg L ^-1 for R-O-desmethylvenlafaxine). The significant differences were observed between S-venlafaxine (11.07 mg L ^-1) and S-O-desmethylvenlafaxine (10.24 mg L ^-1), which were more toxic than R-forms. The half-lives of R- and S-venlafaxine were 0.8 d and 0.5 d in the presence of β-CD, which were obvious shorter than those in alone treatments. In addition, our experiments not only demonstrated that β-CD performed particularly well for removal of venlafaxine and O-desmethylvenlafaxine, it significantly reduces the toxicity of venlafaxine to alga. These results highlight advantages of β-CD relevant to chiral drugs removal and protection of aquatic organisms, which may have a better application for environmental and ecological safety in future.

Reversed phase liquid chromatography for the enantioseparation of local anaesthetics in polysaccharide-based stationary phases. Application to biodegradability studies

A comprehensive study on the chiral separation of bupivacaine, mepivacaine, prilocaine and propanocaine with eight commercial polysaccharide-based chiral stationary phases (CSPs) in reversed phase conditions compatible with MS detection is performed. Methanol and acetonitrile are used as organic modifiers. Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared. The polysaccharide-based CSPs tested present different enantioselectivity towards the analytes. From the results, the experimental conditions for determining the enantiomers of bupivacaine, mepivacaine, prilocaine and propanocaine in saline aqueous samples using MS detection are used, for the first time, to perform an enantioselective biodegradability study.

Ecological risk assessment of fifty pharmaceuticals and personal care products (PPCPs) in Chinese surface waters: A proposed multiple-level system

Interest in the risks posed by trace concentrations of pharmaceuticals and personal care products (PPCPs) in surface waters is increasing, particularly with regard to potential effects of long-term, low-dose exposures of aquatic organisms. In most cases, the actual studies on PPCPs were risk assessments at screening-level, and accurate estimates were scarce. In this study, exposure and ecotoxicity data of 50 PPCPs were collected based on our previous studies, and a multiple-level environmental risk assessment was performed. The 50 selected PPCPs are likely to be frequently detected in surface waters of China, with concentrations ranging from the ng L^-1 to the low-g L^-1, and the risk quotients based on median concentrations ranged from 2046 for nonylphenol to 0 for phantolide. A semi-probabilistic approach screened 33 PPCPs that posed potential risks to aquatic organisms, among which 15 chemicals (nonylphenol, sulfamethoxazole, di (2-ethylhexyl) phthalate, 17β-ethynyl estradiol, caffeine, tetracycline, 17β-estradiol, estrone, dibutyl phthalate, ibuprofen, carbamazepine, tonalide, galaxolide, triclosan, and bisphenol A) were categorized as priority compounds according to an optimized risk assessment, and then the refined probabilistic risk assessment indicated 12 of them posed low to high risk to aquatic ecosystem, with the maximum risk products ranged from 1.54% to 17.38%. Based on these results, we propose that the optimized risk assessment was appropriate for screening priority contaminants at national scale, and when a more accurate estimation is required, the refined probability risk assessment is useful. The methodology and process might provide reference for other research of chemical evaluation and management for rivers, lakes, and sea waters.

Qualitative and quantitative use of micropollutants as source and process indicators. A review

Nowadays, micropollutants such as pharmaceuticals, pesticides and personal care products can be found ubiquitously in the anthropogenically influenced water cycle. As micropollutants have virtually no natural background concentrations they are significantly more sensitive in detecting processes and flow paths than classic inorganic tracers and indicators and at the same time they are often highly source specific. Therefore, using micropollutants as environmental indicators for anthropogenic activities is a common and frequently applied method today. As they interact in many ways with environmental matrices they can be used for source apportionment as well as to estimate flow paths and residence times in waterbodies. This review gives a systematic overview over the large variety of micropollutants used as indicators in the aquatic environment over the last decades together with the prerequisites on their use. Their application is subdivided into their qualitative (compound presence or absence) and quantitative (volume flows) use and shows the numerous possibilities from gaining basic information on the water regime up to advanced applications such as wastewater-based epidemiology.

Guidance of EFSA on risk assessments for active substances of plant protection products that have stereoisomers as components or impurities and for transformation products of active substances that may have stereoisomers

In response to the request of the European Commission to EFSA, this document provides guidance on the information necessary to perform the risk assessment of plant protection active substances that contain stereoisomers in their composition as active components or impurities. The guidance should also be used for active substances that without containing any stereogenic element may generate transformation products or metabolites that do contain them. As a general principle, stereoisomers need to be treated as different chemical components for the risk assessment. Current data requirements in the EU regulatory framework (Regulation (EC) No 1107/2009 and Regulation (EC) No 396/2005) already establish that the substance tested should match the technical specifications (including its isomeric composition) and that formation and effects of metabolites, degradation and transformation products should be investigated (which certainly includes the case when transformation products are stereoisomers). Experience gained during the application of EU pesticides regulation has shown that guidance may be needed to provide applicants and evaluators advice on how to generate and assess the required data. Also, guidance is needed on how to make the best use of the available information to perform the risk assessment of these substances, particularly in situations when the information on individual isomers is not available or difficult to obtain, with a primary objective being to reduce the need for repeating vertebrate animal testing. This guidance does not aim to provide specific technical advice on analytical methods. In this guidance, the Regulation (EU) 283/2013 on the data requirements for the plant protection active substances is analysed and recommendations are given on how to best address and assess data requirements for active substances containing stereoisomers.

This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2019.EN-1693/full

Enantiomer and Carbon Isotope Fractionation of α-Hexachlorocyclohexane by Sphingobium indicum Strain B90A and the Corresponding Enzymes

Chiral organic contaminants, like α-hexachlorocyclohexane (α-HCH), showed isotope fractionation and enantiomer fractionation during biodegradation. This study aims to understand the correlation between these two processes. Initial tests of α-HCH degradation by six Sphingobium strains (with different LinA variants) were conducted. Results showed variable enantiomer selectivity over the time course. In contrast, constant enantiomer selectivity was observed in experiments employing (i) cell suspensions, (ii) crude extracts, or (iii) LinA1 and LinA2 enzymes of strain B90A for α-HCH degradation in enzyme activity assay buffer. The average value of enantioselectivity (ES) were -0.45 ± 0.03 (cell suspensions), -0.60 ± 0.05 (crude extracts), and 1 (LinA1) or -1 (LinA2). The average carbon isotope enrichment factors (ε_c) of (+)α- and (-)α-HCH were increased from cells suspensions (-6.3 ± 0.1‰ and -2.3 ± 0.03‰) over crude extracts (-7.7 ± 0.4‰ and -3.4 ± 0.02‰) to purified enzymes (-11.1 ± 0.3‰ and -3.8 ± 0.2‰). The variability of ES and the ε_c were discussed based on the effect of mass transport and degradation rates. Our study demonstrates that enantiomer and isotope fractionation of α-HCH are two independent processes and both are affected by underlying reactions of individual enzymes and mass transport to a different extent.

Stereoisomer-specific occurrence, distribution, and fate of chiral brominated flame retardants in different wastewater treatment systems in Hong Kong

This study investigated the occurrence and fate of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), two chiral brominated flame retardants (BFRs) with sixteen different stereoisomers, in four Hong Kong wastewater treatment plants (WWTPs) featuring diverse treatment processes during a two-year sampling campaign. More effective HBCD removal was achieved via biodegradation as compared to sludge sorption, whereas both chemically enhanced primary treatment and secondary treatment yielded high TBECH elimination (>90%). α-HBCD (54-75%) predominated in all samples, and its proportions were increased in effluent as compared to influent and sludge. α- and β-TBECH (72.3-84.4% in total) were the predominant TBECH diastereomers, with a proportional shift from the latter to the former diastereomer mostly observed after treatment. More rapid biodegradation and preferential sorption of γ-HBCD as compared to α-HBCD as well as β-TBECH as compared to α-TBECH might account for this changing pattern. This is the first study to report the enantiomer-specific behavior of chiral BFRs in different wastewater treatment processes. A preferential elimination of (+)-α- and (+)-γ-HBCD and E₂-β-TBECH (the second enantiomeric elution order) took place consistently after biological treatment, possibly due to enantioselective adsorption and microbial degradation. Our results highlight the importance of conducting enantiospecific analysis for chiral pollutants in wastewater samples.

Biodegradability and toxicity of monorhamnolipid biosurfactant diastereomers

Synthetic monorhamnolipids differ from biologically produced material because they are produced as single congeners, depending on the β-hydroxyalkanoic acid used during synthesis. Each congener is produced as one of four possible diastereomers resulting from two chiral centers at the carbinols of the lipid tails [(R,R), (R,S), (S,R) and (S,S)]. We compare the biodegradability (CO2 respirometry), acute toxicity (Microtox assay), embryo toxicity (Zebrafish assay), and cytotoxicity (xCELLigence and MTS assays) of synthetic rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-C10-C10) monorhamnolipids against biosynthesized monorhamnolipid mixtures (bio-mRL). All Rha-C10-C10 diastereomers and bio-mRL were inherently biodegradable ranging from 34 to 92% mineralized. The Microtox assay showed all Rha-C10-C10 diastereomers and bio-mRL are slightly toxic according to the US EPA ecotoxicity categories with 5 min EC50 values ranging from 39.6 to 87.5 μM. The zebrafish assay showed that of 22 developmental endpoints tested, only mortality was observed at 120 h post fertilization; all Rha-C10-C10 diastereomers and bio-mRL caused significant mortality at 640 μM, except the Rha-C10-C10 (R,R) which showed no developmental effects. xCELLigence and MTS showed IC50 values ranging from 103.4 to 191.1 μM for human lung cell line H1299 after 72 h exposure. These data provide key information regarding Rha-C10-C10 diastereomers that is pertinent when considering potential applications.

Enantioselective toxic effects and digestion of furalaxyl enantiomers in Scenedesmus obliquus

Research on the enantioselective environmental behavior of chiral pesticides has been a hot spot of environmental chemistry recently. In this study, the acute toxicity and digestion of furalaxyl enantiomers were determined on the aquatic algae Scendesmus obliquus. After exposure for 96 hours, the EC₅₀ values for (S)-furalaxyl and (R)-furalaxyl were 13.59 and 15.26 mg/L, respectively. In addition, enantioselectivity was observed from the determined chlorophyll contents and antioxidant enzyme (CAT and SOD) activities of algae cells after exposure to furalaxyl enantiomers for 96 hours. The digestion rate of (S)-furalaxyl and (R)-furalaxyl were almost the same in S. obliquus. On the basis of these data, the inactive enantiomers (S)- furalaxyl is more toxic than the active one on the non-target species S. obliquus, indicating that such enantiomeric differences should be taken into consideration in the study of pesticide risk assessment.

Trimeprazine is enantioselectively degraded by an activated sludge in ready biodegradability test conditions

A great number of available pharmaceuticals are chiral compounds. Although they are usually manufactured as racemic mixtures, they can be enantioselectively biodegraded as a result of microbial processes. In this paper, a biodegradability assay in similar conditions to those recommended in OECD tests of enantiomers of trimeprazine (a phenothiazine employed as a racemate) is carried out. Experiments were performed in batch mode using a minimal salts medium inoculated with an activated sludge (collected from a Valencian Waste Water Treatment Plant, WWTP) and supplemented with the racemate. The concentration of the enantiomers of trimeprazine were monitored by means of a chiral HPLC method using a cellulose-based chiral stationary phase and 0.5 M NaClO₄/acetonitrile (60:40, v/v) mobile phases. Experiments were performed at three concentration levels of the racemate. In parallel, the optical density at 600 nm (OD600) was measured to control the biomass growth and to connect it with enantioselectivity. The calculated enantiomeric fractions (EF) offer the first evidence of enantioselective biodegradation of trimeprazine. A simplified Monod equation was used as a curve fitting approach for concentration (S), biodegradation (BD), and for the first time, EF experimental data in order to expand the usefulness of the results. Precision studies on S (repeatability conditions) and, for the first time, EF (intermediate precision conditions) were also performed.

Direct chromatographic study of the enantioselective biodegradation of ibuprofen and ketoprofen by an activated sludge

The quantification of the enantiomeric fraction (EF) during the biodegradation process is essential for environmental risk assessment. In this paper the enantioselective biodegradation of ibuprofen, IBU, and ketoprofen, KET, two of the drugs most consumed, was evaluated. Biodegradation experiments were performed in batch mode using a minimal salts medium inoculated with an activated sludge (collected from a Valencian Waste Water Treatment Plant) and supplemented with the racemate of each compound. The inoculum activity was verified using fluoxetine as reference compound. The experimental conditions used (analyte concentration and volume of inoculum) were chosen according to OECD guidelines. In parallel, the optical density at 600 nm was measured to control the biomass growth and to connect it with enantioselectivity. Two RPLC methods for chiral separations of IBU and KET using polysaccharides-based stationary phases were developed. Novel calculations and adapted models, using directly the chromatographic peak areas as dependent variable, were proposed to estimate significant parameters related to the biodegradation process: biodegradation (BD) and EF values at given time, half-life times of (R)- and (S)-enantiomers, number of days to reach a complete BD and the minimum EF expected. The modelled BD and EF curves fitted adequately the data (R² > 0.94). The use of these new equations provided similar results to those obtained using concentration data. However, the use of chromatographic peak areas data, eliminates the uncertainty associated to the use of the calibration curves. The results obtained in this paper indicate that an enantiorecognition towards IBU enantiomers by the microorganisms present in the activated sludge used in this study occurred, being the biodegradation of (R)-IBU higher than that of (S)-IBU. For KET, non-enantioselective biodegradation was observed.

Temporal Changes and Stereoisomeric Compositions of 1,2,5,6,9,10-Hexabromocyclododecane and 1,2-Dibromo-4-(1,2-dibromoethyl)cyclohexane in Marine Mammals from the South China Sea

Stereoisomeric compositions of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) were investigated in the blubber of two species of marine mammals, finless porpoises ( Neophocaena phocaenoides) and Indo-Pacific humpback dolphins ( Sousa chinensis), from the South China Sea between 2005 and 2015. The concentrations of ΣHBCD in samples of porpoise ( n = 59) and dolphin ( n = 32) ranged from 97.2 to 6,260 ng/g lipid weight (lw) and from 447 to 45,800 ng/g lw, respectively, while those of ΣTBECH were both roughly 2 orders of magnitude lower. A significant increasing trend of ΣHBCD was found in dolphin blubber over the past decade. The diastereomeric profiles exhibited an absolute predominance of α-HBCD (mostly >90%), while the proportions of four TBECH diastereomers in the samples appeared similar. A preferential enrichment of the (-)-enantiomers of α-, β-, and γ-HBCD was found in most blubber samples. Interestingly, the body lengths of porpoises showed a significant negative correlation with the enantiomer fractions of α-HBCD. Significant racemic deviations were also observed for α-, γ-, and δ-TBECH enantiomeric pairs. This is the first report of the presence of TBECH enantiomers in the environment. The estimated hazard quotient indicates that there is a potential risk to dolphins due to HBCD exposure.

Investigation of Free-Standing Plasmonic Mesoporous Ag/CMK-8-Nafion Composite Membrane for the Removal of Organic Pollutants with 254-nm UV Irradiation

"Carbon-based material" has demonstrated a great potential on water purification due to its strong physical adsorption to organic pollutants in the water. Three-dimensional cubic ordered mesoporous carbon (CMK-8), one of the well-known ordered mesoporous carbons, was prepared by using nanocasting method with mesoporous silica (KIT-6) as the template. In this study, CMK-8 blended with Nafion polymer to form a free-standing mesoporous CMK-8-Nafion composite membrane. The synthesis of high crystallinity CMK-8 was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). More than 80% methyl orange (MO) removal efficiency was observed under 254-nm UV irradiation after 120 min. Ninety-two percent recycling performance was remained after four recycling tests, which indicated a reliable servicing lifetime for the water purification. Furthermore, an additional layer of plasmonic silver nanoparticles (Ag NPs) was integrated into this CMK-8-Nafion membrane for higher pollutant removal efficiency, attributing from the generation of plasmon-resonance hot electrons from Ag NPs. A 4-in. CMK-8-Nafion composite membrane was also fabricated for the demonstration of potential large-scale utilization.

Chiral pharmaceuticals: A review on their environmental occurrence and fate processes

More than 50% of pharmaceuticals in current use are chiral compounds. Enantiomers of the same pharmaceutical have identical physicochemical properties, but may exhibit differences in pharmacokinetics, pharmacodynamics and toxicity. The advancement in separation and detection methods has made it possible to analyze trace amounts of chiral compounds in environmental media. As a result, interest on chiral analysis and evaluation of stereoselectivity in environmental occurrence, phase distribution and degradation of chiral pharmaceuticals has grown substantially in recent years. Here we review recent studies on the analysis, occurrence, and fate of chiral pharmaceuticals in engineered and natural environments. Monitoring studies have shown ubiquitous presence of chiral pharmaceuticals in wastewater, surface waters, sediments, and sludge, particularly β-receptor antagonists, analgesics, antifungals, and antidepressants. Selective sorption and microbial degradation have been demonstrated to result in enrichment of one enantiomer over the other. The changes in enantiomer composition may also be caused by biologically catalyzed chiral inversion. However, accurate evaluation of chiral pharmaceuticals as trace environmental pollutants is often hampered by the lack of identification of the stereoconfiguration of enantiomers. Furthermore, a systematic approach including occurrence, fate and transport in various environmental matrices is needed to minimize uncertainties in risk assessment of chiral pharmaceuticals as emerging environmental contaminants.

Synthesis and herbicidal activity of optically active α-(substituted phenoxyacetoxy) (substituted phenyl) methylphosphonates

α-(Substituted phenoxyacetoxy) alkylphosphonates containing one chiral carbon atom have been demonstrated to be PDHc inhibitor with good herbicidal activity and some of them could be used as potential herbicide. In order to determine any difference in herbicidal activities between (R) and (S) isomers, the synthetic method of optically active substituted phenylalkylphosphonates IB were explored. A highly practical, enantioselective hydrophosphonylation was developed to prepare optically active O,O-dimethyl α-hydroxyalkylphosphonates 3 as key intermediate by asymmetric addition reaction of dimethylphosphite 1 and several kinds of aldehydes 2 using tridentate Schiff base Al(III) complexes as catalysts. A series of novel O,O-dimethyl α-(substituted phenoxyacetoxy)(substituted phenyl)methylphosphonates IB including (R) and (S) enantiomers were further synthesized with excellent enantioselectivity (95-99% ee) by the condensation of optically active α-hydroxyl (substituted phenyl)methylphosphonates 3 and substituted phenoxyacetyl chlorides 4. The herbicidal activities of title compound IB including their racemates, (R) and (S) enantiomers were evaluated in greenhouse for post-emergence application. All compounds IB showed significant inhibitory activity against dicotyledonous plants. A difference in herbicidal effect among racemate, (R) and (S) enantiomers were observed. Especially IB7 and IB10 showed obvious chiral selectivity in inhibitory activity against chickweed. (S)-IB7 with ED₅₀ of 22.8gai/ha was found to be most effective enantiomer against chickweed and its inhibitory activity was 8.17 times higher than (R)-IB7. (S)-IB7 as potential herbicide would be effective at lower rates than (R)-IB7 or (rac)-IB7.

The potential acute and chronic toxicity of cyfluthrin on the soil model organism, Eisenia fetida

In this study, the acute (72h and 14 d) and chronic (28 d and 8 weeks) effects of cyfluthrin on earthworms were evaluated across different endpoints, which are mortality, growth, reproduction and enzyme activities. Cyfluthrin was rated as moderately toxic in 72-h filter paper test and low toxic in 14-day soil test. The exposure of earthworms to cyfluthrin-polluted soil for 8 weeks showed that growth of earthworms was inhibited by cyfluthrin, cocoon production and hatching were inhibited by 20-60mg/kg cyfluthrin. Moreover, 28-day soil test on the responses of enzymes associated with antioxidation and detoxification showed that the activities of catalase (CAT) and glutathione S- transferase (GST) were initially increased by cyfluthrin at 5-20mg/kg, but reduced at 30-60mg/kg, peroxidase (POD) was increased by 26-102% by cyfluthrin in the early period, except 5mg/kg on day 7, and ethoxyresorufin-O-deethylase (EROD) was increased by 29-335% by cyfluthrin after 3 days. Cyfluthrin degraded with a half-life of 24.8-34.8 d, showing the inconsistency between the continuous toxic responses of earthworms and degradation of cyfluthrin in soil. The variable responses of these indexes indicated that different level endpoints should be jointly considered for better evaluation of the environmental risk of contaminants in soil.

Enantioselective metabolism of triadimefon and its chiral metabolite triadimenol in lizards

Chinese lizards (Eremias argus) were exposed to separated R-(-)-triadimefon, S-(+)-triadimefon and racemic triadimefon to evaluate enantioselective accumulation of triadimefon. After single oral administration of R-(-)-triadimefon, S-(+)-triadimefon and racemic triadimefon, the time-concentration curves in different tissues were found to be different. Triadimefon enantiomers crossed the blood-brain barrier and brain is a main target organ. The residues of triadimefon enantiomers in fat were highest after 24h indicating that fat was the main tissue of accumulation. In racemic triadimefon exposure group, the enantiomer fractions of R-(-)-triadimefon in different tissues showed that the differences between R-(-)-triadimefon and S-(+)-triadimefon were significant in absorption and metabolism, but the differences became smaller in exclusion and accumulation. From the results of mathematical models, S-(+)-triadimefon was absorbed and eliminated faster than R-(-)-triadimefon, and R-(-)-triadimefon was easily distributed in the tissues and more easily converted into its metabolites. Furthermore, among the four enantiomers of triadimenol, SR-(-)-triadimenol produced by S-(+)-triadimefon may have the highest fungicidal activity and the strongest biological toxicity, RR-(+)-triadimenol produced by R-(-)-triadimefon was most likely to bioaccumulate in lizard. Identifying toxicological effects and dose-response relationship of SR-(-)-triadimenol and RR-(+)-triadimenol will help fully assess the risk of TF enantiomers use in the future. The results enrich and supplement the knowledge of the environmental fate of triadimefon enantiomers.

Enantioselective accumulation, metabolism and phytoremediation of lactofen by aquatic macrophyte Lemna minor

Pesticides are frequently detected in water bodies due to the agricultural application, which may pose impacts on aquatic organisms. The enantioselective bioaccumulation and metabolism of the herbicide lactofen in aquatic floating macrophyte Lemna minor (L. minor) were studied and the potential L. minor phytoremediation was investigated. Ultra-high performance liquid chromatography - tandem mass spectrometry (UHPLC-MS-MS) analysis for lactofen and its two known metabolites in L. minor was performed. The initial concentrations of racemic lactofen, R-lactofen and S-lactofen were all 30μgL^-1 in the growth solution. The distribution of lactofen and its metabolites in growth solution and L. minor was determined throughout a 5-d laboratory trial. It was observed that S-lactofen was preferentially taken up and metabolized in L. minor. After rac-lactofen exposure, the accumulation amount of S-lactofen was approximately 3-fold more than that of R-lactofen in L. minor and the metabolism rate of S-lactofen (T_1/2=0.92 d) was significantly faster than R-lactofen (T_1/2=1.55 d). L. minor could only slightly accelerate the metabolism and removal of lactofen in the growth solution. As for the metabolites, desethyl lactofen was found to be the major metabolite in L. minor and the growth solution, whereas the metabolite acifluorfene was undetectable. No interconversion of the two enantiomers was observed after individual enantiomer exposure, indicating they were configurationally stable. The findings of this work represented that the accumulation and metabolism of lactofen in L. minor were enantioselective, and L. minor had limited capacity for the removal of lactofen and its metabolite in water.

Diclofenac in Arabidopsis cells: Rapid formation of conjugates

Pharmaceutical and personal care products (PPCPs) are continuously introduced into the soil-plant system, through practices such as agronomic use of reclaimed water and biosolids containing these trace contaminants. Plants may accumulate PPCPs from soil, serving as a conduit for human exposure. Metabolism likely controls the final accumulation of PPCPs in plants, but is in general poorly understood for emerging contaminants. In this study, we used diclofenac as a model compound, and employed ¹⁴C tracing, and time-of-flight (TOF) and triple quadruple (QqQ) mass spectrometers to unravel its metabolism pathways in Arabidopsis thaliana cells. We further validated the primary metabolites in Arabidopsis seedlings. Diclofenac was quickly taken up into A. thaliana cells. Phase I metabolism involved hydroxylation and successive oxidation and cyclization reactions. However, Phase I metabolites did not accumulate appreciably; they were instead rapidly conjugated with sulfate, glucose, and glutamic acid through Phase II metabolism. In particular, diclofenac parent was directly conjugated with glutamic acid, with acyl-glutamatyl-diclofenac accounting for >70% of the extractable metabolites after 120-h incubation. In addition, at the end of incubation, >40% of the spiked diclofenac was in the non-extractable form, suggesting extensive sequestration into cell matter. The rapid formation of non-extractable residue and dominance of diclofenac-glutamate conjugate uncover previously unknown metabolism pathways for diclofenac. In particular, the rapid conjugation of parent highlights the need to consider conjugates of emerging contaminants in higher plants, and their biological activity and human health implications.

Effects of bifenthrin exposure in soil on whole-organism endpoints and biomarkers of earthworm Eisenia fetida

In this study, toxic effects of bifenthrin in soil on earthworms were evaluated by acute and chronic toxic endpoints combined with a set of biomarkers. Bifenthrin was moderately toxic in 72-h filter paper test and low toxic in 14-d soil test. The exposure of earthworms to bifenthrin-polluted soil for 8 weeks showed that cocoons were inhibited by high dose of bifenthrin, and larvae were stimulated by low dose but inhibited by high dose of bifenthrin. Furthermore, 28-d soil test on the responses of enzymes associated with antioxidation and detoxification in worms showed that peroxidase (POD) was stimulated by bifenthrin, superoxide dismutase (SOD) inhibited in the early period but stimulated in the later period, glutathione S- transferase (GST) inhibited in the later period, and ethoxyresorufin-O-deethylase (EROD) inhibited at day 3 but markedly stimulated at day 28 at high dose. The different responses of these indexes indicated that multi indexes should be jointly taken into account for comprehensive evaluation of the environmental risk of contaminants in soil.

Stereoselective toxicity of etoxazole to MCF-7 cells and its dissipation behavior in citrus and soil

The stereoselective cytotoxicity of new chiral acaricide etoxazole and its dissipation in citrus and soil were investigated for the first time. Enantioselective toxicity and oxidative stress of etoxazole toward MCF-7 cells was conducted. The phenomenon of dose- and form-dependent cytotoxicity was demonstrated by MTT and LDH assays, ROS generation, and SOD and CAT activity alternation. Cytotoxicity ranks were found to be consistent with oxidative damage as (R)- > Rac- > (S)-etoxazole. Moreover, the results of enantioselective degradation showed that (S)-etoxazole degraded faster than its antipode (R)-etoxazole. The gradual raise of EF values indicated the achievement of enantioselective degradation in citrus and soil, leaving the enrichment of (R)-etoxazole isomer. Significant differences of environmental behavior and cytotoxicity of etoxazole enantiomers were found in this study which provided valuable insight into the mechanism of potential toxicity and warranted more careful assessment of this pesticide before its agricultural application.

Joint interpretation of enantiomer and stable isotope fractionation for chiral pesticides degradation

Chiral pesticides are important contaminants affecting the health and functioning of aquatic systems. The combination of stable isotope and enantiomer analysis techniques has been recently proposed to better characterize the fate of these contaminants in natural and engineered settings. We introduce a modeling approach with the aim of unifying and integrating the interpretation of isotopic and enantiomeric fractionation. The model is based on the definition of enantiomer-specific isotopologues and jointly predicts the evolution of concentration, enantiomer fractionation, as well as changes in stable isotope ratios of different elements. The method allows evaluating different transformation pathways and was applied to investigate enzymatic degradation of dichlorprop (DCPP), enzymatic degradation of mecoprop methyl ester (MCPPM), and microbial degradation of α-hexachlorocyclohexane (α-HCH) by different bacterial strains and under different redox conditions. The model accurately reproduces the isotopic and enantiomeric data observed in previous experimental studies and precisely captures the dual-dimensional trends characterizing different reaction pathways. Furthermore, the model allows testing possible combinations of enantiomer analysis (EA), compound specific isotope analysis (CSIA), and enantiomer specific isotope analysis (ESIA) to identify and assess isotope and enantiomer selective reaction mechanisms.

Degradation and enantiomeric fractionation of mecoprop in soil previously exposed to phenoxy acid herbicides - New insights for bioremediation

Phenoxy acid-contaminated subsoils are common as a result of irregular disposal of residues and production wastes in the past. For enhancing in situ biodegradation at reducing conditions, biostimulation may be an effective option. Some phenoxy acids were marketed in racemic mixtures, and biodegradation rates may differ between enantiomers. Therefore, enantio-preferred degradation of mecoprop (MCPP) in soil was measured to get in-depth information on whether amendment with glucose (BOD equivalents as substrate for microbial growth) and nitrate (redox equivalents for oxidation) can stimulate bioremediation. The degradation processes were studied in soil sampled at different depths (3, 4.5 and 6m) at a Danish urban site with a history of phenoxy acid contamination. We observed preferential degradation of the R-enantiomer only under aerobic conditions in the soil samples from 3- and 6-m depth at environmentally relevant (nM) MCPP concentrations: enantiomer fraction (EF)<0.5. On the other hand, we observed preferential degradation of the S-enantiomer in all samples and treatments at elevated (μM) MCPP concentrations: EF>0.5. Three different microbial communities were discriminated by enantioselective degradation of MCPP: 1) aerobic microorganisms with little enantioselectivity, 2) aerobic microorganisms with R-selectivity and 3) anaerobic denitrifying organisms with S-selectivity. Glucose-amendment did not enhance MCPP degradation, while nitrate amendment enhanced the degradation of high concentrations of the herbicide.

Developing a genetic manipulation system for the Antarctic archaeon, Halorubrum lacusprofundi: investigating acetamidase gene function

No systems have been reported for genetic manipulation of cold-adapted Archaea. Halorubrum lacusprofundi is an important member of Deep Lake, Antarctica (~10% of the population), and is amendable to laboratory cultivation. Here we report the development of a shuttle-vector and targeted gene-knockout system for this species. To investigate the function of acetamidase/formamidase genes, a class of genes not experimentally studied in Archaea, the acetamidase gene, amd3, was disrupted. The wild-type grew on acetamide as a sole source of carbon and nitrogen, but the mutant did not. Acetamidase/formamidase genes were found to form three distinct clades within a broad distribution of Archaea and Bacteria. Genes were present within lineages characterized by aerobic growth in low nutrient environments (e.g. haloarchaea, Starkeya) but absent from lineages containing anaerobes or facultative anaerobes (e.g. methanogens, Epsilonproteobacteria) or parasites of animals and plants (e.g. Chlamydiae). While acetamide is not a well characterized natural substrate, the build-up of plastic pollutants in the environment provides a potential source of introduced acetamide. In view of the extent and pattern of distribution of acetamidase/formamidase sequences within Archaea and Bacteria, we speculate that acetamide from plastics may promote the selection of amd/fmd genes in an increasing number of environmental microorganisms.

Enantioselective toxic effects of cyproconazole enantiomers against Chlorella pyrenoidosa

Enantioselectivity in ecotoxicity, digestion and uptake of chiral pesticide cyproconazole to Chlorella pyrenoidosa was studied. The 96h-EC50 values of rac- and the four enantiomers were 9.005, 6.616, 8.311, 4.290 and 9.410 mg/L, respectively. At the concentrations of 8 mg/L and 14 mg/L, the contents of pigments exposed in rac-, enantiomer-2 and 4 were higher than that exposed in enantiomer-1 and 3. The superoxide dismutase (SOD) and catalase (CAT) activity of algae exposed to enantiomer-1 and 3 was higher than that exposed to the rac-, enantiomer-2 and 4 at three levels. In addition, the malondialdehyde (MDA) concentrations in algae disposed with enantiomer-1 and 3 were increased remarkably at three levels. For the digestion experiment, the half-lives of four enantiomers in algae suspension were 28.06, 19.10, 21.13, 15.17 days, respectively. During the uptake experiment, the order of the concentrations of cyproconazole in algae cells was enantiomer-4, 2, 3 and 1. Based on these data, we concluded that ecotoxicity, digestion and uptake of chiral pesticide cyproconazole to C. pyrenoidosa were enantioselective, and such enantiomeric differences must be taken into consideration when assessing the risk of cyproconazole to environment.

Validation of a Chiral Liquid Chromatographic Method for the Degradation Behavior of Flumequine Enantiomers in Mariculture Pond Water

In this work, flumequine (FLU) enantiomers were separated using a Chiralpak OD-H column, with n-hexane-ethanol (20:80, v/v) as the mobile phase at a flow rate of 0.6 mL/min. Solid phase extraction (SPE) was used for cleanup and enrichment. The limit of detection, limit of quantitation, linearity, precision, and intra/interday variation of the chiral high-performance liquid chromatography (HPLC) method were determined. The developed method was then applied to investigate the degradation behavior of FLU enantiomers in mariculture pond water samples. The results showed that the degradation of FLU enantiomers under natural, sterile, or dark conditions was not enantioselective. Chirality 28:649-655, 2016. © 2016 Wiley Periodicals, Inc.