Retention Modelling of Phenoxy Acid Herbicides in Reversed-Phase HPLC under Gradient Elution.

Phenoxy acid herbicides are used worldwide and are potential contaminants of drinking water. Reversed phase high-performance liquid chromatography (RP-HPLC) is commonly used to monitor phenoxy acid herbicides in water samples. RP-HPLC retention of phenoxy acids is affected by both mobile phase composition and pH, but the synergic effect of these two factors, which is also dependent on the structure and pKa of solutes, cannot be easily predicted. In this paper, to support the setup of RP-HPLC analysis of phenoxy acids under application of linear mobile phase gradients we modelled the simultaneous effect of the molecular structure and the elution conditions (pH, initial acetonitrile content in the eluent and gradient slope) on the retention of the solutes. In particular, the chromatographic conditions and the molecular descriptors collected on the analyzed compounds were used to estimate the retention factor k by Partial Least Squares (PLS) regression. Eventually, a variable selection approach, Genetic Algorithms, was used to reduce the model complexity and allow an easier interpretation. The PLS model calibrated on the retention data of 15 solutes and successively tested on three external analytes provided satisfying and reliable results.

2,4-dichlorophenoxyacetic acid (2,4-D) micropollutant herbicide removing from water using granular and powdered activated carbons: a comparison applied for water treatment and health safety.

Activated carbons are well-known porous materials as an effective adsorbent used for the removal of emerging contaminants, such as herbicides, which are increasingly present in water bodies. Most water treatment plants, specially in Brazil, are unable to completely remove such contaminants by the conventional process and advanced treatment using activated carbons is required. The aim of this paper was to verify the influence of the activated carbons granulometry and specific surface area on the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide removal efficiency using distilled-deionized water and filtered water collected from a conventional Water Treatment Plant. Commercial activated carbons samples used in this work were obtained from two different manufacturers. Activated carbons were analyzed by the specific surface area, pore size and volume distribution, nuclear magnetic resonance, infrared and x-ray spectroscopy, moisture, volatile matter and ash contents. Batch adsorption isotherms experiments were used and performed by Langmuir and Freundlich models. Granular and powdered activated carbons removed over 99% of 2,4-D in distilled water and near to 99% using filtered water. The activated carbons evaluated in this work presented high performance and played a key role in water treatment by removing 2,4-D herbicide, ensuring the protection of human health and the ecosystem.

High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments.

Activated biocarbons were prepared using biomass wastes: sugarcane bagasse, coconut shell and endocarp of babassu coconut; as a renewable source of low-cost raw materials and without prior treatments. These activated biocarbons were characterized by textural analysis, solid-state 13C nuclear magnetic resonance spectroscopy, X-ray diffraction and scanning electronic microscopy. Textural analysis results revealed that those activated biocarbons were microporous, with specific surface area values of 547, 991 and 1,068 m2 g-1 from sugarcane bagasse, coconut shell and endocarp of babassu coconut, respectively. The innovation of this work was to evaluate which biomass residue was able to offer the best performance in removing 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from water by adsorption. Adsorption process of 2,4-D was investigated and the Langmuir and Redlich-Peterson models described best the adsorption process, with R2 values within 0.96-0.99. The 2,4-D removal performance were 97% and 99% for the coconut and babassu biocarbons, respectively. qM parameter values obtained from Langmuir model were 153.9, 233.0 and 235.5 mg g-1 using sugarcane bagasse, coconut shell and endocarp of babassu, respectively. In addition, the adsorption kinetics were described nicely by the second-order model and the Gibbs free energy parameter values were negative, pointing to a spontaneous adsorption, as well.

Monodisperse cobalt(II) based metal-organic coordination polymer beads as a sorbent for solid-phase extraction of chlorophenoxy acid herbicides prior to their quantitation by HPLC.

Metal-organic coordination polymer beads (MOCBs) are described for use as a sorbent for solid-phase extraction of chlorophenoxy herbides. By applying regulation of Co(II) ions, micro-sized monodisperse MOCBs were obtained through the microwave heating. The MOCBs-based method displays excellent extraction efficiency towards chlorophenoxy herbicides, specifically of 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 4-chloromethylphenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid and 2-(2,4-dichlorophenoxy)propionic acid. Following extraction, the herbicides were eluted with 8% formic acid in methanol and quantified by HPLC. The method, when applied to analyze spiked cereals, exhibits a wide linear range (from 0.6 to 1000 ng g-1) and low limits of quantification (ranging from 0.10 to 0.25 ng g-1). For a single column, the inter-day and intra-day precisions, expressed as the relative standard deviation are in the range of 2.5-6.8%. The batch-to-batch reproducibility (for n = 3) is <4.6%. For spiked cereal samples, relative recoveries are very good (90.3-102.3%, for n = 4). The extraction efficiency of MOCBs remains unchanged after reusing for 40 times. Graphical abstractSchematic presentation of Co(II)-doped metal-organic coordination polymer beads (Co(II)@MOCB) using for solid-phase extraction (SPE).

A 3D-Printed, Portable, Optical-Sensing Platform for Smartphones Capable of Detecting the Herbicide 2,4-Dichlorophenoxyacetic Acid.

Onsite rapid detection of herbicides and herbicide residuals in environmental and biological specimens are important for agriculture, environmental concerns, food safety, and health care. The traditional method for herbicide detection requires expensive laboratory equipment and a long turnaround time. In this work, we developed a single-stripe microliter plate smartphone-based colorimetric device for rapid and low-cost in-field tests. This portable smartphone platform is capable of screening eight samples in a single-stripe microplate. The device combined the advantages of small size (50 × 100 × 160 mm3) and low cost ($10). The platform was calibrated by using two different dye solutions, i.e. methyl blue (MB) and rhodamine B, for the red and green channels. The results showed good correlation with results attained from a traditional laboratory reader. We demonstrated the application of this platform for detection of the herbicide 2,4-dichlorophenoxyacetic acid in the range of 1 to 80 ppb. Spiked samples of tap water, rat serum, plasma, and human serum were tested by our device. Recoveries obtained varied from 95.6% to 105.2% for all of the spiked samples using the microplate reader and from 93.7% to 106.9% for all of the samples using the smartphone device. This work validated that the smartphone optical-sensing platform is comparable to the commercial microplate reader; it is eligible for onsite, rapid, and low-cost detection of herbicides for environmental evaluation and biological monitoring.

Adsorption of 2,4-Dichlorophenoxyacetic Acid from an Aqueous Solution on Fly Ash.

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on fly ash was studied. The effects of adsorbent dose, contact time, pH, ionic strength, and temperature on the adsorption were investigated. Adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models, and results showed that adsorption kinetics were better represented by the pseudo-second order model. Adsorption isotherms of 2,4-D on fly ash were analyzed using the Freundlich and Langmuir models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was spontaneous and endothermic. The negative values of ΔG° and the positive value of ΔH° indicate the spontaneous nature of 2,4-D adsorption on fly ash, and that the adsorption process was endothermic. Results showed that fly ash is an efficient, low-cost adsorbent for removal of 2,4-D from water.

Small (13)C/(12)C fractionation contrasts with large enantiomer fractionation in aerobic biodegradation of phenoxy acids.

Phenoxy acid herbicides are important groundwater contaminants. Stable isotope analysis and enantiomer analysis are well-recognized approaches for assessing in situ biodegradation in the field. In an aerobic degradation survey with six phenoxyacetic acid and three phenoxypropionic acid-degrading bacteria we measured (a) enantiomer-specific carbon isotope fractionation of MCPP ((R,S)-2-(4-chloro-2-methylphenoxy)-propionic acid), DCPP ((R,S)-2-(2,4-dichlorophenoxy)-propionic acid), and 4-CPP ((R,S)-2-(4-chlorophenoxy)-propionic acid); (b) compound-specific isotope fractionation of MCPA (4-chloro-2-methylphenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid); and (c) enantiomer fractionation of MCPP, DCPP, and 4-CPP. Insignificant or very slight (ε = -1.3‰ to -2.0‰) carbon isotope fractionation was observed. Equally small values in an RdpA enzyme assay (εea = -1.0 ± 0.1‰) and even smaller fractionation in whole cell experiments of the host organism Sphingobium herbicidovorans MH (εwc = -0.3 ± 0.1‰) suggest that (i) enzyme-associated isotope effects were already small, yet (ii) further masked by active transport through the cell membrane. In contrast, enantiomer fractionation in MCPP, DCPP, and 4-CPP was pronounced, with enantioselectivities (ES) of -0.65 to -0.98 with Sphingomonas sp. PM2, -0.63 to -0.89 with Sphingobium herbicidovorans MH, and 0.74 to 0.97 with Delftia acidovorans MC1. To detect aerobic biodegradation of phenoxypropionic acids in the field, enantiomer fractionation seems, therefore, a stronger indicator than carbon isotope fractionation.

Fabrication of In2S3 nanoparticle decorated TiO2 nanotube arrays by successive ionic layer adsorption and reaction technique and their photocatalytic application.

In2S3 nanoparticle (NP) decorated self-organized TiO2 nanotube array (In2S3/TiO2 NT) hybrids were fabricated via simple successive ionic layer adsorption and reaction (SILAR) technique. The In2S3 NPs in a size of about 15 nm were found to deposit on the top surface of the highly oriented TiO2 NT while without clogging the tube entrances. The loading amount of In2S3 NPs on the TiO2 NT was controlled by the cycle number of SILAR deposition. Compared with the bare TiO2 NT, the In2S3/TiO2 NT hybrids showed stronger absorption in the visible light region and significantly enhanced photocurrent density. The photocatalytic activity of the In2S3/TiO2 NT photocatalyst far exceeds that of bare TiO2 NT in the degradation of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light. After 160-min irradiation, almost 100% 2,4-D removal is obtained on the 7-In2S3/TiO2 NT prepared through seven SILAR deposition cycles, much higher than 26% on the bare TiO2 NT. After 10 successive cycles of photocatalytic process with total 1,600 min of irradiation, In2S3/TiO2 NT maintained as high 2,4-D removal efficiency as 95.1% with good stability and easy recovery, which justifies the potential of the photocatalytic system in application for the photocatalytic removal of organic pollutants such as herbicides or pesticides from water.

Photo-Fenton degradation of phenol, 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol mixture in saline solution using a falling-film solar reactor.

In this work, a saline aqueous solution of phenol, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) was treated by the photo-Fenton process in a falling-film solar reactor. The influence of the parameters such as initial pH (5-7), initial concentration of Fe2+ (1-2.5mM) and rate of H202 addition (1.87-3.74mmol min-1) was investigated. The efficiency of photodegradation was determined from the removal of dissolved organic carbon (DOC), described by the species degradation of phenol, 2,4-D and 2,4-DCP. Response surface methodology was employed to assess the effects of the variables investigated, i.e. [Fe2+], [H202] and pH, in the photo-Fenton process with solar irradiation. The results reveal that the variables' initial concentration of Fe2+ and H202 presents predominant effect on pollutants' degradation in terms of DOC removal, while pH showed no influence. Under the most adequate experimental conditions, about 85% DOC removal was obtained in 180 min by using a reaction system employed here, and total removal of phenol, 2,4- and 2,4-DCP mixture in about 30min.

Ultrasound-assisted emulsification microextraction combined with injection-port derivatization for the determination of some chlorophenoxyacetic acids in water samples.

An efficient method based on ultrasound-assisted emulsification microextraction followed by injection-port derivatization GC analysis was developed to determine 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) in natural water samples. In this procedure, 12.5 µL of 1-undecanol was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample of the analytes located inside an ultrasonic water bath. The resulting emulsion was centrifuged, and 1 µL of the separated organic solvent together with 1 µL of the derivatization reagent were injected into a GC equipped with a flame ionization detector. Several factors that influence the derivatization and extraction were optimized. Under the optimal conditions, the LODs were 0.33 and 1.7 µg/L for MCPA and 2,4-D, respectively. Preconcentration factors of 670 and 836 were obtained for MCPA and 2,4-D, respectively. The precision of the proposed method was evaluated in terms of repeatability, which was <5.7% (n = 5). The applicability of the proposed method was evaluated by extraction and determination of chlorophenoxyacetic acids from some natural waters, which indicated that the matrices of natural waters have no significant effect on the extraction and derivatization efficiency of this method.

Plasmid-mediated bioaugmentation of sequencing batch reactors for enhancement of 2,4-dichlorophenoxyacetic acid removal in wastewater using plasmid pJP4.

Plasmid-mediated bioaugmentation was demonstrated using sequencing batch reactors (SBRs) for enhancing 2,4-dichlorophenoxyacetic acid (2,4-D) removal by introducing Cupriavidus necator JMP134 and Escherichia coli HB101 harboring 2,4-D-degrading plasmid pJP4. C. necator JMP134(pJP4) can mineralize and grow on 2,4-D, while E. coli HB101(pJP4) cannot assimilate 2,4-D because it lacks the chromosomal genes to degrade the intermediates. The SBR with C. necator JMP134(pJP4) showed 100 % removal against 200 mg/l of 2,4-D just after its introduction, after which 2,4-D removal dropped to 0 % on day 7 with the decline in viability of the introduced strain. The SBR with E. coli HB101(pJP4) showed low 2,4-D removal, i.e., below 10 %, until day 7. Transconjugant strains of Pseudomonas and Achromobacter isolated on day 7 could not grow on 2,4-D. Both SBRs started removing 2,4-D at 100 % after day 16 with the appearance of 2,4-D-degrading transconjugants belonging to Achromobacter, Burkholderia, Cupriavidus, and Pandoraea. After the influent 2,4-D concentration was increased to 500 mg/l on day 65, the SBR with E. coli HB101(pJP4) maintained stable 2,4-D removal of more than 95 %. Although the SBR with C. necator JMP134(pJP4) showed a temporal depression of 2,4-D removal of 65 % on day 76, almost 100 % removal was achieved thereafter. During this period, transconjugants isolated from both SBRs were mainly Achromobacter with high 2,4-D-degrading capability. In conclusion, plasmid-mediated bioaugmentation can enhance the degradation capability of activated sludge regardless of the survival of introduced strains and their 2,4-D degradation capacity.

Diamino moiety functionalized silica nanoparticles as pseudostationary phase in capillary electrochromatography separation of plant auxins.

A novel and simple method for the preparation of silica nanoparticles having surface-functionalized diamino moiety (dASNPs) was reported in our paper and characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, and thermogravimetry techniques. To test this method practically, in this contribution we describe the enhanced separation of four plant auxins - indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 2,4-dichlorophenoxyacetic acid (dCPAA), and 2-(1-naphthyl) acetic acid (NAA) - by capillary electrochromatography using diamino moiety functionalized silica nanoparticles as pseudostationary phase (PSP) in the running buffer. The effect of pH, buffer concentration, and diamino moiety functionalized silica nanoparticles concentration on the selectivity of separation was investigated. A combination of the nanoparticles and running buffer reversed the electroosmotic direction making possible the rapid and efficient separation of the auxins from the auxins migrated in the same direction with the EOF under optimum experimental conditions. A good resolution of four auxins was obtained within 5.5 min under optimum experimental conditions. The precision (RSD, n = 5) was in the range of 0.72-0.91% and 1.89-2.23% for migration time and peak area response, respectively. The detection limits were 0.48, 0.44, 0.46, and 0.42 µM for NAA, IBA, IAA, and dCPAA, respectively. Furthermore, the method was successfully tested for the determination of IAA in the grapes.

Applicability of multisyringe chromatography coupled to on-line solid-phase extraction to the simultaneous determination of dicamba, 2,4-D, and atrazine.

Simultaneous determination of three herbicides (dicamba, 2,4-D, and atrazine) has been achieved by on-line solid-phase extraction (SPE) coupled to multisyringe chromatography (MSC) with UV detection. The preconcentration conditions were optimized; a preconcentration flow rate of 0.5 mL min(-1) and elution at 0.8 mL min(-1) were the optimum conditions. A C(18) (8 mm i.d.) membrane extraction disk conditioned with 0.3 mol L(-1) HCl in 0.5% MeOH was used. A 3-mL sample was preconcentrated, then eluted with 0.43 mL 40:60 water-MeOH. A C(18) monolithic column (25 mm × 4.6 mm) was used for chromatographic separation. Separation of the three compounds was achieved in 10 min by use of 0.01% aqueous acetic acid-MeOH (60:40) as mobile phase at a flow rate of 0.8 mL min(-1). The limits of detection (LOD) were 13, 57, and 22 µg L(-1) for dicamba, 2,4-D, and atrazine, respectively. The sampling frequency was three analyses per hour, and each analysis consumed only 7.3 mL solvent. The method was applied to spiked water samples, and recovery between 85 and 112% was obtained. Recovery was significantly better than in the conventional HPLC-UV method. These results indicated the reliability and accuracy of this flow-based method. This is the first time this family of herbicides has been simultaneously analyzed by on-line SPE-MSC using a monolithic column.

Application of NaClO-treated multiwalled carbon nanotubes as solid phase extraction sorbents for preconcentration of trace 2,4-dichlorophenoxyacetic acid in aqueous samples.

Multiwalled carbon nanotubes functionalized by oxidation of original multiwalled carbon nanotubes with NaClO were prepared and their application as solid phase extraction sorbent for 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated systemically, and a new method was developed for the determination of trace 2,4-D in water samples based on extraction and preconcentration of 2,4-D with solid phase extraction columns packed with NaClO-treated multiwalled carbon nanotubes prior to its determination by HPLC. The optimum experimental parameters for preconcentration of 2,4-D, including the column activating conditions, the amount of the sorbent, pH of the sample, elution composition, and elution volume, were investigated. The results indicated 2,4-D could be quantitatively retained by 100 mg NaClO-treated multiwalled carbon nanotubes at pH 5, and then eluted completely with 10 mL 3:1 (v/v) methanol-ammonium acetate solution (0.3 mol/L). The detection limit of this method for 2,4-D was 0.15 µg/L, and the relative standard deviation was 2.3% for fortified tap water samples and 2.5% for fortified riverine water sample at the 10 µg/L level. The method was validated using fortified tap water and riverine water samples with known amount of 2,4-D at the 0.4, 10, and 30 µg/L levels, respectively.

Degradation of 2,4-dichlorophenoxyacetic acid by a halotolerant strain of Penicillium chrysogenum: antibiotic production.

The extensive use of pesticides in agriculture has prompted intensive research on chemical and biological methods in order to protect contamination of water and soil resources. In this paper the degradation of the pesticide 2,4-dichlorophenoxyacetic acid by a Penicillium chrysogenum strain previously isolated from a salt mine was studied in batch cultures. Co-degradation of 2,4-dichlorophenoxyacetic acid with additives such as sugar and intermediates of pesticide metabolism was also investigated. Penicillium chrysogenum in solid medium was able to grow at concentrations up to 1000 mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D) with sucrose. Meanwhile, supplementation of the solid medium with glucose and lactose led to fungal growth at concentrations up to 500 mg/L of herbicide. Batch cultures of 2,4-D at 100 mg/L were developed under aerobic conditions with the addition of glucose, lactose and sucrose, showing sucrose as the best additional carbon source. The 2,4-D removal was quantified by liquid chromatography. The fungus was able to use 2,4-D as the sole carbon and energy source under 0%, 2% and 5.9% NaCl. The greatest 2,4-D degradation efficiency was found using alpha-ketoglutarate and ascorbic acid as co-substrates under 2% NaCl at pH 7. Penicillin production was evaluated in submerged cultures by bioassay, and higher amounts of beta-lactam antibiotic were produced when the herbicide was alone. Taking into account the ability of P. chrysogenum CLONA2 to degrade aromatic compounds, this strain could be an interesting tool for 2,4-D herbicide remediation in saline environments.

2,4-D removal via denitrification using volatile fatty acids.

Many countries have waters contaminated with both herbicides and nitrates; however, information is limited with respect to removal rates for combined nitrate and herbicide elimination. This research investigates the removal of 2,4-D via denitrification, with a particular emphasis on the effect of adding naturally generated volatile fatty acids (VFAs). The acids were produced from an acid-phase anaerobic digester with a mean VFA concentration of 3153±801 mg/L (as acetic acid). Initially, 2,4-D degrading bacteria were developed in an SBR fed with both sewage and 2,4-D (30-100 mg/L). Subsequent denitrification batch tests demonstrated that the specific denitrification rate increased from 0.0119±0.0039 using 2,4-D alone to 0.0192±0.0079 g NO3-N/g VSS per day, when 2,4-D was combined with natural VFAs from the digester. Similarly, the specific 2,4-D consumption rate increased from 0.0016±0.0009 using 2,4-D alone to 0.0055±0.0021 g 2,4-D/g VSS per day, when using 2,4-D plus natural VFAs. Finally, a parallel increase in the percent 2,4-D removal was observed, rising from 28.33±11.88 using 2,4-D alone to 54.17±21.89 using 2,4-D plus natural VFAs.

Clinical study and observation on the effect of hemoperfusion therapy treatment on central nervous system injury in patients with 2,4-dichlorophenoxyacetic acid poisoning.

OBJECTIVE: To evaluate the curative effect of hemoperfusion therapy on central nervous system injury in patients with 2,4-dichlorophenoxyacetic acid poisoning. PATIENTS AND METHODS: A total of 60 patients with 2,4-dichlorophenoxyacetic acid poisoning were enrolled in this study. They were admitted to the Emergency Department of Qinghai Provincial People's Hospital from 2015 to 2018 and were randomly divided into two groups by random number table method. One group was control group (routine treatment group), and the other group was the treatment group (hemoperfusion therapy was added on the basis of routine treatment). Glasgow coma score (GCS), APACHE II score, and MMSE score were used to evaluate the effects before treatment and 7 days after treatment. The results were statistically analyzed. RESULTS: After treatment, GCS in the treatment group was higher than that in the control group, while APACHE II score was lower than that in the control group, and MMSE score was significantly higher than that in the control group, with statistically significant difference (p<0.05). The effective rate in the control group was only 26.67%, and that in the treatment group was 86.67%, with statistically significant difference (c2=19.62, p<0.001). CONCLUSIONS: Hemoperfusion therapy can promote the recovery of central nervous system in patients with 2,4-dichlorophenoxyacetic acid poisoning, reduce the injury of other organs, and significantly reduce the mortality of patients.

Evaluation of the genotoxic and cytotoxic effects of exposure to the herbicide 2,4-dichlorophenoxyacetic acid in Astyanax lacustris (Pisces, Characidae) and the potential for its removal from contaminated water using a biosorbent.

The genotoxic and cytotoxic effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on specimens of Astyanax lacustris were evaluated using different biomarkers. Additionally, this study evaluated the efficiency of an activated carbon filter made from the husks green coconut, which was used as a biosorbent to remove 2,4-D dissolved in the water, and the potential effectiveness of this procedure for the reduction of the toxic effects of this compound on A. lacustris. Three sublethal concentrations of 2,4-D (10, 20, and 40 mg L-1) were tested over 24, 48, and 72 h, and their effects on Astyanax lacustris were evaluated using chromosomal aberration test, the mitotic index, the frequency of micronuclei and nuclear alterations, and the comet assay. Exposure to 2,4-D increased the frequency of chromosomal aberrations, reduced the mitotic index, and caused significant levels of nuclear modification in some of the treatments, in comparison with the negative control. The comet assay revealed DNA damage (classes 1-3) at all 2,4-D concentrations, reaching significant levels in the 20 mg L-1 (48 h) and 40 mg L-1 (72 h) treatments. The coconut husk biosorbent was highly effective for the removal of 2,4-D and the fish exposed to the water decontaminated by this filter had low levels of cellular alteration. The findings of the present study demonstrated, for the first time, the genotoxic and cytotoxic effects of 2,4-D in Astyanax lacustris, as well as suggests the potential application of a biosorbent for the effective decontamination of water contaminated with pesticides.

Efficient Degradation of Phenoxyalkanoic Acid Herbicides by the Alkali-Tolerant Cupriavidus oxalaticus Strain X32.

Phenoxyalkanoic acid (PAA) herbicides are mainly metabolized by microorganisms in soils, but the degraders that perform well under alkaline environments are rarely considered. Herein, we report Cupriavidus oxalaticus strain X32, which showed encouraging PAA-degradation abilities, PAA tolerance, and alkali tolerance. In liquid media, without the addition of exogenous carbon sources, X32 could completely remove 500 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) or 4-chloro-2-methylphenoxyacetic acid within 3 days, faster than that with the model degrader Cupriavidus necator JMP134. Particularly, X32 still functioned at pH 10.5. Of note, with X32 inoculation, we observed 2,4-D degradation in soils and diminished phytotoxicity to maize (Zea mays). Furthermore, potential mechanisms underlying PAA biodegradation and alkali tolerance were then analyzed by whole-genome sequencing. Three modules of tfd gene clusters involved in 2,4-D catabolism and genes encoding monovalent cation/proton antiporters involved in alkali tolerance were putatively identified. Thus, X32 could be a promising candidate for the bioremediation of PAA-contaminated sites, especially in alkaline surroundings.

Chirally functionalized anion-exchange type silica monolith for enantiomer separation of 2-aryloxypropionic acid herbicides by non-aqueous capillary electrochromatography.

A silica based monolithic capillary column derivatized with O-9-(tert-butylcarbamoyl)quinidine was prepared for CEC enantiomer separation of chiral 2-aryloxypropionic acid herbicides including inter alia dichlorprop, mecoprop and fenoprop. The silica monolith had a relatively low surface coverage with chiral cationic selector moieties. Due to the low selector density retention factors were low as well, yet still enabling enantiomer separations of the target solutes. Both electrophoretically and chromatographically dominated migration and separation modes, respectively, could be established depending on the employed conditions. In the former mode, enantiomers migrated in front of the EOF marker, and faster separations and higher plate numbers could be achieved. In the latter mode, stronger adsorption translated into a typical chromatographic separation in which the enantiomers eluted after the EOF marker whereby separation factors were slightly enhanced compared to the aforementioned separation mode. Reasonable baseline separations of enantiomers were accomplished for all analytes after optimization of relevant mobile phase parameters in the anion-exchange CEC system including sample loadability, and the separations were comparable to such obtained on an optimized high density quinidine-carbamate modified organic polymer monolith column. Overall, it is concluded that monoliths with a high surface density of chiral ion-exchange moieties are favorable because of their enhanced sample loadabilities and improved chromatographic performance with regard to separation factors, plate numbers and peak symmetries. The resultant accompanying longer analysis times may rather be reduced by adjusting effective column length than by reducing selector coverage of the monolith.