Study of the degradation of diphenyl-ether herbicides aclonifen and bifenox in different environmental waters.

The degradation of the diphenyl-ether herbicides aclonifen (ACL) and bifenox (BF) in water samples has been studied under different laboratory conditions, using in-tube solid-phase microextraction (IT-SPME) coupled to capillary liquid chromatography (capLC). The working conditions were selected in order to detect also bifenox acid (BFA), a compound formed as a result of the hydroxylation of BF. Samples (4 mL) were processed without any previous treatment, which allowed the detection of the herbicides at low ppt levels. The effects of temperature, light and pH on the degradation of ACL and BF have been tested using standard solutions prepared in nanopure water. The effect of the sample matrix has been evaluated by analysing different environmental waters spiked with the herbicides, namely ditch water, river water and seawater. The kinetics of the degradation have been studied and the half-life times (t1/2) have been calculated. The results obtained have demonstrated that the sample matrix is the most important parameter affecting the degradation of the tested herbicides. The degradation of both ACL and BF was much faster in ditch and river water samples, where t1/2 values of only a few days were observed. However, both compounds showed a better stability in seawater samples, where they can persist for several months. In all matrices ACL was found to be more stable than BF. In samples where BF had been substantially degraded, BFA was also detected, although the stability of this compound was also limited. Other degradation products have been detected along the study.

Magnetic ZIF-8-Based Mimic Multi-enzyme System as a Colorimetric Biosensor for Detection of Aryloxyphenoxypropionate Herbicides.

In the present study, a magnetic mimic multi-enzyme system was developed by encapsulating the aryloxyphenoxypropionate (AOPP) herbicide hydrolase QpeH and alcohol oxidase (AOx) in zeolitic imidazolate framework (ZIF-8) nanocrystals with magnetic Fe3O4 nanoparticles (MNPs) to detect AOPP herbicides. The structural, protein loading capacity and loading ratio, porosity, and magnetic properties of QpeH/AOx@mZIF-8 were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen sorption, and vibrating sample magnetometry. An AOPP herbicide colorimetric biosensor made with QpeH/AOx@mZIF-8 had the highest sensitivity toward quizalofop-P-ethyl (QpE) with a limit of detection of 8.2 µM. This system was suitable to detect two other AOPP herbicides, including fenoxaprop-P-ethyl (FpE) and haloxyfop-P-methyl (HpE). The practical application of the biosensor was verified through quantitative analysis of QpE residues in industrial wastewater and field soils. Furthermore, QpeH/AOx@mZIF-8 exhibited excellent long-term storage stability (at least 50 days), easy separation by magnet, and reusability (at least 10 cycles), supporting its promising role in simple and low-cost detection of AOPP herbicides in real environmental samples.

[Determination of three diphenyl ether herbicides in rice by magnetic solid phase extraction using Fe3O4@MOF-808 coupled with high performance liquid chromatography].

The complex matrix of rice samples and the small amount of the target analytes in the sample necessitate an effective pretreatment process to enrich the target analytes and minimize matrix interference before instrumental analysis. Magnetic solid phase extraction (MSPE) is a dispersive solid phase extraction technique which allows for the rapid separation of sorbents from the sample solution under an external magnetic field. Compared with other traditional solid phase extraction methods, MSPE has the advantages of convenient operation, minimal interference and absence of column pressure. In this work, a metal organic framework composite (Fe3O4@MOF-808) was synthesized by a facile solvothermal method for using as an effective adsorbent to concentrate nitrofen (NIT), oxyfluorfen (OXY) and bifenox (BIF) in rice samples. Based on the pretreatment, a method was developed by coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared material was characterized by Fourier-transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy and vibrating sample magnetometry measurements for determining its functional groups, morphology and magnetic strength. The results showed that MOF-808 has a regular octahedral morphology and well-dispersed, and the particle size of the material ranged from 400 to 500 nm with a smooth surface. The spherical Fe3O4 particles were uniformly attached to the surface of the octahedral MOF-808 crystals. The maximum saturation magnetization of this composite was 40.35 emu/g which is lower than the saturation magnetization Fe3O4 (78.26 emu/g) but still sufficient for the requirements of MSPE. The prepared Fe3O4@MOF-808 was used in the MSPE of three diphenyl ether herbicides (Des) in rice. As is well known, the key factors influencing MSPE are the adsorption and elution processes. In order to establish the optimal extraction conditions, the adsorption parameters (adsorbent amount, extraction time, elution solvent and elution volume) were investigated in detail. A 15 mL mixed standard solution was used in the experiment, and the concentrations of the three Des were 65 ng/mL. All the experiments were performed in parallel three times. The effects of the dosages of Fe3O4@MOF-808 (10, 15, 20, 25 and 30 mg), adsorption time (2, 4, 6, 8 and 10 min), elution solvents (acetone, acetonitrile and methanol) and elution volume (0.5 mL, 0.5 mL×2, 0.5 mL×3, 0.5 mL×4) were investigated. The Des could be adsorbed completely by using 25 mg of Fe3O4@MOF-808 for no more than 6 min. Elution was performed with 0.5 mL×2 of methanol. Various parameters such as limits of detection (LODs), limits of quantification (LOQs), accuracy and precision of the method were evaluated. The method showed good linearity in the range of 2-300 µg/L (r > 0.998). The LODs and LOQs were 0.6, 0.6, 0.4 µg/kg and 2.0, 2.0,1.5 µg/kg for NIT, OXY, BIF respectively. At spiked levels of 5, 10 and 20 µg/kg, the recoveries ranged from 87.3% to 96.7% with relative standard deviations (RSDs) less than 10.8%. The enrichment factors (EFs) of the method for the three Des were between 25 and 29. The method was applied to the pretreatment of the three Des in real samples, and none of the Des could be detected at any of the samples. This method had a lower LOD than that of the national standard method, but its LOD and recovery were similar to those of other reference methods. In summary, the developed method has the advantages of operational simplicity, rapidity and accuracy, and it is suitable for the analysis of herbicide residues in rice samples.

Proline-Modified UIO-66 as Nanocarriers to Enhance Candida rugosa Lipase Catalytic Activity and Stability for Electrochemical Detection of Nitrofen.

Immobilization can be used to improve the stability of lipases and enhances lipase recovery and reusability, which increases its commercial value and industrial applications. Nevertheless, immobilization frequently causes conformational changes of the lipases, which decrease lipase catalytic activity. in the present work, we synthesized UIO-66 and grafted UIO-66 crystals with proline for immobilization of Candida rugosa lipase (CRL). As indicated by steady-state fluorescence microscopy, grafting of proline onto UIO-66 crystals induced beneficial conformational change in CRL. CRL immobilized on UIO-66/Pro (CRL@UIO-66/Pro) demonstrated higher enzyme activity and better recyclability than that immobilized on UIO-66 (CRL@UIO-66) in both hydrolysis (CRL@UIO-66/Pro: 0.34 U; CRL@UIO-66: 0.15 U) and transesterification (CRL@UIO-66/Pro: 0.93 U; CRL@UIO-66: 0.25 U) reactions. The higher values of kcat and kcat/Km of CRL@UIO-66/Pro also showed that it had better catalytic efficiency as compared to CRL@UIO-66. It is also worth noting that CRL@UIO-66/Pro (0.93 U) demonstrated a much higher transesterification activity as compared to free CRL (0.11 U), indicating that UIO-66/Pro has increased the solvent stability of CRL. Both CRL@UIO-66 and CRL@UIO-66/Pro were also used for the fabrication of biosensors for nitrofen with a wide linear range (0-100 µM), lower limit of detection, and good recovery rate.

LC-MS/MS analysis of BADGE, NOGEs, and their derivatives migrated from food and beverage metal cans.

A simple and novel method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated to determine the levels of 10 compounds (bisphenol A diglycidyl ether (BADGE), novolac-glycidyl ethers (NOGEs), and their related compounds) migrated from food and beverage cans into food simulants. Method validation showed acceptable linearity, precision, and accuracy. The detection limits ranged from 0.28 to 14.8 µg L-1, and the quantification limits ranged from 0.94 to 49.3 µg L-1. Water, 4% acetic acid, 50% ethanol, and n-heptane were employed as food simulants for the migration tests, and the developed LC-MS/MS method was applied to 104 epoxy-coated beverage and food metal cans. Only BADGE∙2H2O and BADGE were detected; the levels were below the specific migration limit. Based on the obtained migration results, the estimated daily intakes (EDIs) of BADGE∙2H2O and BADGE were calculated. Exposure assessments were conducted to compare the EDI with the tolerable daily intake (TDI), with a relatively low percentage of the TDI being reported. NOGE and its related compounds were not detected in the monitored cans. Long-term storage tests were also conducted at 60°C over 30 days. Only BADGE∙2H2O was detected in all food simulants, except for n-heptane, and the maximum amount detected was 114.6 µg L-1 in 50% ethanol.

Debromination of polybrominated diphenyl ethers (PBDEs) by palladized zerovalent zinc particles: Influence factors, pathways and mechanism.

We synthesized a novel material, namely palladized zero-valent zinc (Pd/ZVZ), and investigated its efficiency for the degradation of polybrominated diphenyl ethers (PBDEs). The plated Pd significantly enhances the degradation rate of PBDEs by ZVZ at the optimum loading of 1% by weight. In the Pd/ZVZ system, very few lower BDEs were accumulated during the degradation of 2,2',4,4'- tetrabromodiphenyl ether (BDE-47) and the final product is diphenyl ether, whereas the ZVZ system only debrominates BDE-47 to di-BDE and further debromination becomes very difficult. The degradation rates of BDEs by ZVZ greatly decreased with decreased bromination level, while in Pd/ZVZ system, the degradation rates of PBDEs did not show a significant difference. These indicate different mechanisms. This was confirmed by investigating the debromination pathways of the PBDEs in both systems. We determined that a H-transfer was the dominant mechanism in the Pd/ZVZ system. In addition, the reactivity of Pd/ZVZ to BDE-47 is pH-independent, which has a great advantage for various applications over ZVZ alone. Our study provides a new approach for the remediation of the PBDEs pollution.

Persistence behaviour and safety risk evaluation of pyridalyl in tomato and cabbage.

A field experiment was set up to evaluate persistence behaviour of pyridalyl in tomato, cabbage and cultivated field soil over two consecutive seasons. An analytical method was developed to analyze pyridalyl residues in different matrices and duly validated, based on single laboratory method validation criteria. Pyridalyl residues were detected and quantified using a gas chromatograph equipped with an electron capture detector. The compound exhibited low persistence in tomato, cabbage and soil. A safe waiting period of 17-18 d after final insecticide application needs to be maintained before harvesting the crop. Both dietary and soil ecological risk were assessed and it was found that the harvested vegetables were toxicologically safe for consumption. However, there was concern about insecticidal toxicity against the algal population of soil which needs to be reconfirmed by further studies.

Differential pulse voltammetric determination of the carcinogenic diamine 4,4'-oxydianiline by electrochemical preconcentration on a MoS2 based sensor.

An electrochemical sensor for the carcinogen 4,4'-oxydianiline (Oxy) is described. The method is based on the ability of MoS2 nanosheets to preconcentrate Oxy. A glassy carbon electrode (GCE) was covered, by drop-casting, with MoS2 nanosheets that were obtained by exfoliation. X-Ray photoemission spectroscopy indicates that Oxy accumulates on the MoS2 nanosheets through an electropolymerization process similar to that reported for aniline. Both electrochemical impedance spectroscopy and atomic force microscopy were used to characterize the electrode surface at the different stages of device fabrication. Employing the current measured at +0.27 V vs. Ag/AgCl after Oxy adsorption, the modified GCE enables the voltammetric detection of Oxy at 80 nM levels with relative errors and relative standard deviations of <8.3 and <5.6%, respectively, at all the concentrations studied. The method was applied to the selective determination of Oxy in spiked river water samples. Very good selectivity and recoveries of around 95% in average are found. Graphical abstractSchematic representation of 4,4-oxydianiline electrochemical polymerization and preconcentration onto molybdenum disulfide nanosheets for the diamine determination in river waters.

Determination of the in vitro metabolic stability and metabolites of the anticancer derivative riccardin D-N in human and mouse hepatic S9 fractions using HPLC-Q-LIT-MS.

Riccardin D-N (RD-N) is an aminomethylated derivative of the macrocyclic bisbibenzyl compound riccardin D (RD), which has shown stronger activity against cancer cells than RD. However, there has been no research on the metabolism of RD-N. The present study aimed to characterize the in vitro metabolism and metabolic stability of RD-N after incubation with mouse and human hepatic S9 fractions using high performance liquid chromatography-hybrid triple quadrupole/linear ion trap mass spectrometry (HPLC-Q-LIT-MS). Multiple ion monitoring (MIM) and multiple reaction monitoring (MRM)-information dependent acquisition-enhanced product ion (MIM/MRM-IDA-EPI) scans were used to identify the metabolites formed. MRM scans were also used to quantify the changes in the amount of RD-N and to semi-quantify the main metabolites. Twenty-eight metabolic products were detected and 25 structures were predicted. Hydroxylation, dehydrogenation, glucuronidation, and methylation were proposed to be the principle metabolic pathways in the in vitro incubation with human and mouse hepatic S9 fractions. There were differences in the number and abundance of RD-N metabolites between the human and mouse hepatic S9 fractions. RD-N was shown to have good metabolic stability. After 2 h of incubation, 44% of the original RD-N remained in the human hepatic S9 fraction compared with 22% in the mouse. The major metabolites of RD-N, M4, M8, M20 and M21, were monitored semi-quantitatively using the typical transitions. Finally, HPLC-Q-LIT-MS was used for the identification and quantitation of the metabolites of R D-N, which is a simple and efficient method to rapidly screen potential drug candidates.

Phytochemical analysis of flower from Pandanus odorifer (Forssk.) Kuntze for industrial application.

Pandanus odorifer (Forssk.) Kuntze is an economically important aromatic plant. The essential oil from male flowers is widely used in aromatherapy, cosmetics and as food flavouring agent. Phenylethyl methyl ether (PEME), the major constituent of essential oil, gives the chief characteristic fragrance to the oil. In the present study, 180 samples from 12 different regions were collected and hydrodistilled for essential oil isolation. The oil was then subjected to GC and GC-MS analysis to find out the percentage of the constituents. The results revealed PEME as the major constituent ranging from 58.03 to 81.86% and terpinen-4-ol, the second major constituent ranging from 7.81 to 21.46%. Soil nitrogen was found to be the most influential factor for oil yield and PEME content. The flowers containing high essential oil yield and PEME content could be used as elite chemotypes with enough potential for large-scale commercial cultivation to meet the demand of kewda industries.

Potentiometric perchlorate determination at nanomolar concentrations in vegetables.

In this work, an expeditious method based on the multi-commutated flow-analysis concept with potentiometric detection is proposed to perform determinations of the emergent contaminant perchlorate in vegetable matrices down to nanomolar concentration. To accomplish the task, a tubular shaped potentiometric sensor selective to perchlorate ion was constructed with a PVC membrane containing 12mmol/kg of the polyamine bisnaphthalimidopropyl-4,4'-diaminodiphenylmethane and 2-nitrophenyl phenyl ether 68% (w/w) as plasticizer casted on a conductive epoxy resin. Under optimal flow conditions, the sensor responded linearly in the concentration range of 6.3×10-7-1.0×10-3mol/L perchlorate. In order to extend the determinations to lower concentrations (4.6(±1.3)×10-10mol/L perchlorate), a column packed with 70mg of sodium 2,5,8,11,14-pentaoxa-1-silacyclotetradecane-polymer was coupled to the flow-system thus enabling prior pre-concentration of the perchlorate. The proposed procedure provides a simpler alternative for the determination of perchlorate in foods, nowadays only allowed by sophisticated and expensive equipment and laborious methods.

Occurrence of bisphenols, bisphenol A diglycidyl ethers (BADGEs), and novolac glycidyl ethers (NOGEs) in indoor air from Albany, New York, USA, and its implications for inhalation exposure.

Bisphenols, bisphenol A diglycidyl ethers (BADGEs), and novolac glycidyl ethers (NOGEs) are used in the production of epoxy resins and polycarbonate plastics. Despite the widespread application of these chemicals in household products, studies on their occurrence in indoor air are limited. In this study, 83 indoor air samples were collected in 2014 from various locations in Albany, New York, USA, to determine the concentrations of bisphenols, BADGEs (refer to BADGE and its derivatives), and NOGEs (refer to NOGE and its derivatives) and to calculate inhalation exposure to these compounds. Among eight bisphenols measured, BPA, BPF, and BPS were found in bulk air (i.e., vapor plus particulate phases), at geometric mean (GM) concentrations of 0.43, 0.69 and 0.09 ng m(-3), respectively. Among 11 BADGEs and NOGEs determined, BADGE·2H2O was the predominant compound found in indoor air (detection rate [DR]: 85.5%), at concentrations as high as 6.71 ng m(-3). Estimation of inhalation exposure to these chemicals for various age groups showed that teenagers had the highest exposure doses to BPA, BPF, BPS, and BADGE·2H2O at 5.91, 9.48, 1.24, and 3.84 ng day(-1), respectively. The body weight-normalized estimates of exposure were the highest for infants, with values at 0.24, 0.39, 0.05, and 0.16 ng kg bw(-1) day(-1) for BPA, BPF, BPS, and BADGE·2H2O, respectively. This is the first survey to report inhalation exposure to bisphenols, BADGEs, and NOGEs.

Bioefficacy evaluation and dissipation pattern of nanoformulation versus commercial formulation of pyridalyl in tomato (Solanum lycopersicum).

A study was undertaken to evaluate the decline of the residues of pyridalyl in tomatoes grown in two different cultivation systems: open field (conventional cultivation) and net house (pot experiment). Field experiment was conducted with commercial (10 EC) and nanoformulation of pyridalyl on tomato crop. Tomato plants were subjected to pesticide spray, when fruits were close to ripeness. Fruit samples were taken periodically and cleaned up using QuEChERS methodology, and the residue of pyridalyl was analyzed by ultrahigh-performance liquid chromatography (UHPLC). It dissipated in tomato fruit following the first-order kinetics. In field, average initial deposit of pyridalyl in tomato was observed to be 0.222 and 0.371 µg g(-1) at recommended and double the recommended application rate, respectively, using nanoformulation while it was 0.223 and 0.393 µg g(-1) on using commercial formulation, respectively. The half-life (t1/2) value of nanopyridalyl in tomato fruit was 2.8 and 3.2 days while for commercial formulation, it was 2.5 and 2.6 days for recommended and double the recommended dose, respectively. In India, maximum residue limit (MRL) on tomato has not been fixed for pyridalyl but its residues were always below European MRLs (5 µg g(-1)) on tomato at both application rates. The results of terminal residue showed that pyridalyl residues were below the available MRL. Low residues in tomatoes suggested that this pesticide is safe to use under the recommended dosage. No statistical differences were observed between the cultivation systems in relation to the residue levels of pyridalyl.

Occurrence of Bisphenol A Diglycidyl Ethers (BADGEs) and Novolac Glycidyl Ethers (NOGEs) in Archived Biosolids from the U.S. EPA's Targeted National Sewage Sludge Survey.

Epoxy resins incorporating bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) are used in a wide range of applications, including adhesives, structural and electrical laminates. However, little is known about the occurrence of BADGE, NOGE, and their derivatives in the environment. Using liquid chromatography-tandem mass spectrometry, BADGE, bisphenol F glycidyl ether (BFDGE), 3-ring NOGE, and eight of their derivatives (BADGE·2 H2O, BADGE·H2O, BADGE·HCl·H2O, BADGE·2 HCl, BADGE·HCl, BFDGE·2 H2O, and BFDGE·2 HCl) were determined in archived biosolid samples collected from 68 wastewater treatment plants (WWTPs) from the northeastern, midwestern, western, and southern regions of the USA. BADGE·2 H2O was the most frequently detected (DR = 99%) and the most abundant compound found (median: 93.6 ng/g dry weight [dw]) in this family. The highest total concentrations of target chemicals, ranging from 83.6 to 2490 ng/g dw, were found in biosolids collected from the northeastern United States. The sum of geometric mean (GM) concentration of BADGE, NOGE, and their derivatives in biosolids increased with the treatment capacity of WWTPs. Based on the measured concentrations in biosolids and predicted mass in wastewater, it was estimated that approximately 3.5% of the total production of BADGEs was emitted through WWTP discharges.

Residue, dissipation, and safety evaluation of pyridalyl nanoformulation in Okra (Abelmoschus esculentus [L] Moench).

A comparative study on residues and rate of dissipation of a new nanoformulation of pyridalyl and commercial pyridalyl was carried out on okra under net house and field conditions. Okra crop was sprayed with commercial and nanoformulation of pyridalyl at recommended (75 g a. i./ha) and double the recommended dose (150 g a. i./ha) at the time of fruiting. Quantitation of residues of pyridalyl in okra was done by ultra high performance liquid chromatography over a period of 15 days, and recovery of the method ranged from 79 to 87 %. The half life calculated from the dissipation pattern of pyridalyl on okra for commercial and developed nanoformulation proved that residues of nanopyridalyl did not persist much longer than that of conventional formulation in net house as well as in field trials. The risk quotient value of pyridalyl in okra was significantly lower than 1, implying its negligible risk to the humans.

Methodology and determination of tetradecabromo-1, 4-diphenoxybenzene flame retardant and breakdown by-products in sediments from the Laurentian Great Lakes.

Tetradecabromo-1,4-diphenoxybenzene (TeDB-DiPhOBz) is a brominated polyphenyl ether flame retardant (FR) that is known to photolytically degrade to produce lower brominated polybrominated-diphenoxybenzenes (PB-DiPhOBzs), which may be precursors to MeO-PB-DiPhOBzs recently reported in the Great Lakes herring gulls eggs. To our knowledge, there are no reports on TeDB-DiPhOBz or other PB-DiPhOBz by-products in any environmental sample. The present study analyzed for the presence of PB-DiPhOBzs (including TeDB-DiPhOBz) and MeO-PB-DiPhOBzs in surficial sediment from sites in Saginaw Bay in western Lake Huron (n = 7), and in comparison to southern Lake Huron (open water) (n = 5) and Lake Erie (n = 3) sediment collected in the summers of 2012 or 2013. To analyze for possible PB-DiPhOBzs (Br14­Br0), the first known analytical method was developed for extraction and cleanup of sediment samples, and analysis by HPLC­atmospheric pressure photoionization (−)-quadrupole time-of-flight-mass spectrometry. The overall recovery efficiency was optimized to on average 33­104% progressing from Br14- to Br10-PB-DiPhOBzs. Br10- to Br14-PB-DiPhOBz detection and quantification limits ranged from 0.05 to 0.15 ng g(−1) dw and 0.17 to 0.49 ng g(−1) dw, respectively. Although this is the first report, PB-DiPhOBzs (Br14­Br10) and MeO-PB-DiPhOBzs were not detectable in any sediment sample. This included a site near the mouth of the highly FR-contaminated Saginaw River, near the confined disposal facility (CDF) located in Saginaw Bay at Channel-Shelter Island, which receives dredged sediment from the Saginaw River. Our findings suggest sediments from the presently studied sites in the Great Lakes ecosystem are not a sink for TeDB-DiPhOBz and PB-DiPhOBz by-product contaminants.

Enantioselective metabolism of the chiral herbicide diclofop-methyl and diclofop by HPLC in loach (Misgurnus anguillicaudatus) liver microsomes in vitro.

An efficient and reliable enantioseparation method by high-performance liquid chromatography (HPLC) for the chiral herbicide diclofop-methyl (DM) and its primary metabolite diclofop (DC) was developed and validated, and the biological process of the enantiomers in loach liver microsomes (LLM) in vitro was investigated. The enantiomers of DM and DC were first separated on an immobilized-type stationary phase of Chiralpak IC. The best resolutions were achieved under the chromatographic condition of n-hexane/IPA/TFA 96:4:0.1(v/v/v) at 20°C with each Rs>2 and the two pairs of enantiomers could be eluted in about 10min. The extraction recoveries of the analytes from LLM were 79.6-108.9% with RSD≤11.5%. The enzyme kinetics of DM enantiomers were different, with the Km value 320.7 for (S)-DM and 392.1 for (R)-DM. The metabolism experiment in vitro showed DM underwent a rapid phase-I metabolism with or without NADPH, indicating the esterases in liver played a dominant role. No interconversion between the two enantiomers was observed by single-enantiomer incubation. The preferential degradation of (S)-DM was confirmed with the half-time (t1/2) of (S)-DM 5.27min and 21.2min for (R)-DM. DC enantiomer was generated by its corresponding ester form and could not be further degraded during the incubation. It was the first study on biotransformation of DM and DC enantiomers in LLM in vitro. The results may help to evaluate the ecological risks of chiral pesticides.

[Rapid determination of six preservative residues in fruits and vegetables by high performance liquid chromatography using dispersive solid phase extraction].

A dispersive solid phase extraction-high performance liquid chromatographic (HPLC) method was established for the simultaneous determination of 2,4-D, thiabendazole, 2-naphthol, o-phenyl phenol, diphenyl ether and biphenyl in the fruits and vegetables. The samples were vortexed for extraction with acetonitrile containing sodium chloride and anhydrous magnesium sulfate. The acetonitrile extraction was purified by acidic alumina dispersed solid phase extraction. The analysis was performed on an Agilent TC C18 column (250 mm x 4.6 mm, 5 microm) and an ultraviolet detector at 235 nm with a mobile phase of methanol-0.02 mol/L (pH 6) potassium dihydrogen phosphate solution, at a flow rate of 1.0 mL/min with gradient elution. Good linearities were observed in the range of 0.5-20 mg/L with correlation coefficients greater than 0.99. The average recoveries of the six preservatives in fruits and vegetables were in the range of 84.2% -99. 1% at three spiked levels of 1, 2 and 10 mg/kg (n = 6) and the relative standard deviations (RSDs) were in the range of 1.67%-10.3%. The limits of quantification were 1 mg/kg. This method is simple, accurate and suitable for the determination of the six preservatives in fruits and vegetables.

Combined isotope and enantiomer analysis to assess the fate of phenoxy acids in a heterogeneous geologic setting at an old landfill.

Phenoxy acid herbicides and their potential metabolites represent industrial or agricultural waste that impacts groundwater and surface waters through leaching from old landfills throughout the world. Fate assessment of dichlorprop and its putative metabolite 4-CPP (2-(4-chlorophenoxy)propionic acid) is frequently obstructed by inconclusive evidence from redox conditions, heterogeneous geologic settings (e.g. clay till) and ambiguous parent-daughter relationships (i.e. 4-CPP may be daughter product or impurity of dichlorprop). For the first time, a combination of four methods was tested to assess transformation of phenoxy acids at a contaminated landfill (Risby site): analysis of (i) parent and daughter compound concentrations, (ii) enantiomer ratios (iii) compound-specific isotope analysis and (iv) enantiomer-specific isotope analysis. Additionally, water isotopes and chloride were used as conservative tracers to delineate two distinct groundwater flow paths in the clay till. Metabolite concentrations and isotope ratios of chlorinated ethenes demonstrated dechlorination activity in the area with highest leachate concentrations (hotspot) indicating favorable conditions also for dechlorination of dichlorprop to 4-CPP and further to phenoxypropionic acid. Combined evidence from concentrations, enantiomer ratios and isotope ratios of dichlorprop and 4-CPP confirmed their dechlorination in the hotspot and gave evidence for further degradation of 4-CPP downgradient of the hotspot. A combination of 4-CPP enantiomer and isotope analysis indicated different enantioselectivity and isotope fractionation, i.e. different modes of 4-CPP degradation, at different locations. This combined information was beyond the reach of any of the methods applied alone demonstrating the power of the new combined approach.

Tribromophenoxy flame retardants in the Great Lakes atmosphere.

The 2,4,6-tribromophenoxy moiety is a common structural feature of several brominated flame retardants, and we have previously reported on the environmental concentrations of one such compound, 1,2-bis(2,4,6-tribromophenoxy) ethane (TBE). Here we report the atmospheric concentrations of TBE and three other tribromophenoxy compounds: allyl 2,4,6-tribromophenyl ether (ATE), 2-bromoallyl 2,4,6-tribromophenyl ether (BATE), and 2,3-dibromopropyl 2,4,6-tribromophenyl ether (DPTE). The samples were collected at five sites near the shores of the Great Lakes during the period 2008-2009, inclusive. Of these four compounds, TBE and ATE are currently used as flame retardants, and DPTE was formerly used as a flame retardant until its production ceased in the mid-1980s. The total concentrations of ATE, BATE, and DPTE were ∼2 pg/m³ in the cities of Chicago and Cleveland and 0.1-0.4 pg/m³ at the rural and remote sites. The concentrations of TBE were ∼1 pg/m³ in these cities and 0.2-0.8 pg/m³ at the rural and remote sites. In both cases, this was a very significant urban effect. The concentrations of ATE, BATE, and DPTE did not change significantly over the two-year study, but the concentrations of TBE decreased by about a factor of 2 during this time. This temporal change was statistically significant but not strong compared to the urban effect.