Application of modified magnetic nanoparticles with amine groups as an efficient solid sorbent for simultaneous removal of 2,4-Dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid from aqueous solution: optimization and modeling

In the present work, functionalized magnetic nano-adsorbent with amine groups (Fe₃O₄@SiO₂@NH₂) was prepared for the simultaneous removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solution. Characterization such as Fourier transform infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscope confirmed that the magnetic nanoparticles structure of Fe₃O₄@SiO₂ nano-adsorbent was successfully functionalized by amine groups. The impact of some influencing parameters such as contact time, pH, adsorbent dosage, 2,4-D and MCPA initials concentration and solution temperature were studied. The equilibrium data were analyzed by Langmuir and Freundlich adsorption isotherms and also two models kinetically of pseudo-first-order and pseudo-second-order. Findings of the present study showed that the synthesized amino-functionalized MNPs will be helpful in use as an effective recyclable adsorbent for the removal of phenoxy acid herbicides from aqueous solution due to its advantages such as facile and rapid separation of target molecules from solution.     

Solid-phase extraction preconcentration of 2,4-dichlorophenoxyacetic acid on silica with immobilized polyethoxylated isooctylphenol groups

Silica with immobilized polyethoxylated isooctylphenol groups (SiO ₂ -TX) is studied as an adsorbent for the solid-phase extraction preconcentration of pesticides based on chlorophenoxyalkanecarboxylic acids from aqueous solutions. It is demonstrated that 2,4-dichlorophenoxyacetic acid (2,4-D) is efficiently (up to 96%) extracted as an ion associate with cetyltrimethylammonium bromide (CTMAB) with SiO₂-TX in the pH range 8–10. The optimum CTMAB-to-2,4-D molar ratio is 200: 1. The capacity of SiO₂-TX to 2,4-D in the Henry region is 0.42 mg/g of adsorbent, and the distribution coefficients reach 9 × 10² mL/g. It is shown that 2,4-D is quantitatively eluted with 1–2 mL of acetonitrile, which allowed us to use the adsorbent in a preconcentration cartridge before determining pesticides by HPLC. The procedure allowed pesticides to be recovered from aqueous solutions in concentrations beginning from 0.025 mg/L.     

Synthesis and crystal structures of lanthanide complexes with foliage growth regulator: phenoxyalkanoic acid

Reactions of Ln(ClO₄)₃?·?6H₂O (Ln=La(III), Eu(III), Nd(III)), 1,10-phenanthroline (phen) and phenoxyacetic acid (PA) or 2,4-dichlorophenoxyacetic acid (2,4-D) yield [La(PA)₂ (phen)₂]₂(ClO₄)₂ (1), [Eu(2,4-D)₂(phen)₂]₂(ClO₄)₂ (2) and [Nd(2,4-D)₃(C₂H₅OH)] _n (3). Compounds 1–3 are characterized by elemental analyses, IR, UV–Vis, ESI-MS spectra and TGA. 1 is also characterized by ¹H and ¹³C NMR. Single crystal X-ray diffraction analyses reveal that 1 and 2 are binuclear, and 3 has a one-dimensional polymeric structure. The La(III), Eu(III) and Nd(III) are nine-coordinate with a distorted tricapped trigonal-prism geometry.     

1-D Chain lanthanide coordination polymers based on mixed 2,4-dichlorophenoxyacetate and 1,10-phenanthroline ligands: crystal structures and luminescent properties

Two new isostructural 1-D lanthanide coordination polymers, {[Ln(2,4-dcp)₃(phen)] _n [(Ln?=?Eu (1); Tb (2)], [2,4-dcp?=?2,4-dichlorophenoxyacetate, phen?=?1,10-phenanthroline], were obtained under hydrothermal conditions and characterized by IR spectroscopy, elemental analyses, thermogravimetry analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. Both structures exhibit similar 1-D infinite chains with a {Ln₂(2,4-dcp)₆(phen)₂} dimeric repeat unit, with lanthanides in an eight-coordinate environment. The results of thermal analysis indicate that 1 and 2 are quite stable to heat. 3-D fluorescence spectra of 1 and 2 were detected at room temperature under excitation and the emission wavelengths of 250–460?nm and 420–750?nm with the same interval of 5?nm, respectively. Interestingly, 1 and 2 possess longer fluorescence lifetimes than other complexes (τ?=?1.61?ms for 1 at 611?nm; 1.79?ms for 2 at 543?nm).     

Detection of 2,4-Dichlorophenoxyacetic Acid by Microtiter Particle Agglutination Inhibition Test and Polarisation Fluoroimmunoassay

Abstract

A simple microtiter particle agglutination inhibition (MPAI) assay for detection of 2,4-dichlorphenoxyacetic acid (2,4-D) has been developed on the basis of coloured polyacrolein latex particles sensitized with monoclonal antibodies to 2,4-D. MPAI test has been applied to the quantification of 2,4-D in water and extracts from grain and compared with the polarisation fluoroimmunoassay. The detection limit of 2,4-dichlorphenoxyacetic acid in MPAI was 0.6 μg/1 which was about two orders higher than that of polarisation fluoroimmunoassay. The cross-reactivity of various structurally related substances was less than 10.%. Good correlation of MPAI and polarisation fluoroimmunoassay was shown when testing 2,4-D in the extracts from grain. MPAI assay is rapid, robust, easy to perform, doesn't need any instrumentation and specially trained personnel.     

Dechlorination of 2,4-dichlorophenoxyacetic acid using biochar-supported nano-palladium/iron: Preparation,characterization, and influencing factors

In the present study, peanut shell, a green waste raw material, was used to prepare biochar (BC) and to obtain BC-supported nano-palladium/iron (BC-nPd/Fe) composites for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from water. Characterization analysis demonstrated that nPd/Fe particles were well dispersed on the BC surface with weakened magnetic properties. The average particle diameter and specific surface area of nPd/Fe were 101.3 nm and 6.7 m² g⁻¹, whereas the corresponding values of the BC-nPd/Fe materials were 88.8 nm and 14.8 m² g⁻¹, respectively. Several factors were found to influence the dechlorination of 2,4-D, including the weight ratio of BC to Fe, Pd loading ratio, initial solution pH, 2,4-D concentration, and reaction temperature. Dechlorination results indicated that the 2,4-D removal and phenoxyacetic acid (PA) generation rates were 44.1% and 20.1%, respectively, in the nPd/Fe system, and 100.0% and 92.1%, respectively, in the BC-nPd/Fe system. The dechlorination of 2,4-D was well described by the pseudo-first-order kinetic model (R² > 0.97), and the observed rate constants k_obs were 0.0042 min (nPd/Fe) and 0.0578 min (BC-nPd/Fe), respectively. The reaction mechanism indicated that the dechlorination hydrogenation was the main process to remove 2,4-D from water in the BC-nPd/Fe system. In addition, BC inhibited the formation of a passivation layer on the particle surface during the reaction, thus maintaining the high reactivity of BC-nPd/Fe. The easy preparation technique, high 2,4-D dechlorination capacity, and mild reaction conditions suggest that BC-nPd/Fe may be a promising alternative composite to remove 2,4-D from water.     

Synthesis,structures, and properties of lead(II) and cobalt(II) metal-organic frameworks based on a flexible benzophenone-2,4′-dicarboxylic acid (H2bpdc)

Two new coordination polymers, [Pb(bpdc)] _n (1) and [Co(bpdc)(phen)] _n (2) [H₂bpdc?=?benzophenone-2,4′-dicarboxylic acid, phen?=?1,10-phenanthroline], have been synthesized and structurally characterized. Hydrogen bonding and π?···?π stacking extend 1 and 2 into 3-D supramolecular architectures, where 1 exhibits a 3-D framework with 1-D hairpin-like helicates based on Pb–O covalent bonds and 2 displays a 3-D network with 1-D zipper-like chains based on Co–O and Co–N covalent bonds. The FT-IR spectra, PXRD and TG analyses are discussed for 1 and 2. Fluorescence spectra and luminescent lifetime are studied for 1.     

A Fast,Simple Method for Analysis of Phenoxy Acid Salt and Ester Formulations by High Performance Liquid Chromatography

Abstract

Salt formulations of 2,4-D (2,4-dichlorophenoxyacetic acid), 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) and dichlorprop [2-(2,4-dichlorophenoxy)propanoic acid] have been analysed by reversed-phase HPLC using a C18-column with 50:50 (v/v) acetonitrile/2% acetic acid as eluant. Internal and external standard HPLC methods are compared.

Ester formulations of 2,4-D and 2,4,5–T are analysed, without hydrolysis, on the same column using 60:40 (v/v) acetonitrile/2% acetic acid as eluant. The method has been used in this laboratory to determine free phenoxy acid in ester formulations, and for the identification of esters in mixed ester formulations.

The methods are fast and accurate, and offer some advantages over previously-described methods.     

Immunodetection of Herbicide 2,4-Dichlorophenoxyacetic Acid by Field-Effect Transistor-Based Biosensors

Abstract

An immunosensor method for determination of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was developed. It is based on the use of the competition between 2,4-D in analyzed probes and 2,4-D-peroxidase conjugate for binding with antibodies being immobilized on porous photo-activated cellulose membranes. These membranes were attached to the gate region of pH-sensitive field transistor (FET) and electrochemical detection of enzyme activity was carried out. Mixture of ascorbic acid (0.1 mM), o-phenylenediamine (1.0 mM), hydrogen peroxide (1.0 mM) was used as substrate solution. The initial rate of pH-shift of the FETs gate region was recorded as measured parameter.

The developed system permits to determine 2,4-D in water solutions for concentrations down to 1 ng/ml. This portable and inexpensive immunosensor meets modern requirements as analytical system for ecological monitoring.     

Studies on the Physical Chemistry of (2,4-Dichlorophenoxy)acetic Acid in Two-phase Systems: Organic Solvent-Water

The dissociation constants (p _s K _a ) of 2,4-D acid were determined in methanol-water mixtures of 10.9 to 38.9 wt.% methanol content. The Yasuda-Shedlovsky procedure was used to obtain the pK _a value in zero-% methanol. The distribution of 2,4-D acid in twelve two-phase organic solvent + water systems and its dimerization in the organic phase were investigated. Values of the distribution coefficient (D _HR), distribution constant (K _D ), and dimerization constant (K _dim) of 2,4-D were obtained. The influence of the structure and polarity of the investigated organic solvents, as well as that of pH of the aqueous phase, on the physical chemistry of 2,4-D in the two-phase systems are described.     

Pyridazine Derivative and Related Compound,Part 18:1 Pyridazino [3′,4′:3,4]pyrazolo [5,1-c]-1,2,4-triazine-3-carboxylic Acid: Synthesis,Reactions, and Antimicrobial Activity

A series of 3-substituted pyridazino[3′,4′:3,4]pyrazolo[5,1-c]-1,2,4-triazens have been synthesized starting from the 3-carboxylic acid derivative 2. The reaction of the acid chloride 3 with amines gave the corresponding anilides 4. The reaction of 2 with ethyl chloroformate and sodium azide in the presence of triethyl amine gave the carbonyl azide 5, which underwent a Curtius rearrangement in boiling ethanol to afford the carbamate 6, which converted to the 3-amino derivative 7 upon alkaline hydrolysis, and the reaction with acid chloride resulted in N-substituted products 9. On other hand, the reaction of the carboxylic acid 2 with POCl₃ and thiosemicarbazide afforded 2-amino-1,3,4-thiadiazole derivative 13. The condensation of 13 with aldehydes furnished 14 in a good yield. The products were screened for their antimicrobial activity against six microorganisms.     

Syntheses and structural characterizations of three transition metal coordination complexes based on flexible 2,4-dichlorophenoxyacetate (2,4-DCP)

Three transition metal coordination complexes, {[Co(2,4-DCP)₂(μ ₂-H₂O)(H₂O)₂]?·?(H₂O)₂} _n (1), [Zn(2,4-DCP)(IN)] _n (2), and [Mn₂(2,4-DCP)₃(DMPY)₂(μ ₂-H₂O)(H₂O)]?·?(2,4-DCP)?·?0.2(H₂O) (3) (2,4-DCP?=?2,4-dichlorophenoxyacetate, IN?=?isonicotinate, DMPY?=?5,5′-dimethyl-2,2′-bipyridine), have been prepared under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Complex 1 displays a 1-D chain through cobalt and bridging water molecules with Co?···?Co distance of 4.028(2)?Å. Complex 2 shows a 2-D (4,4) net, which is extended into a 3-D supramolecular framework by weak hydrogen-bonding interactions. Complex 3 consists of discrete dinuclear cations, 2,4-DCP counter ions and free water molecules, which are assembled into a packing structure through π?···?π stacking of inversion-related DMPY ligands and hydrogen bonds. Magnetic susceptibility measurements show weak antiferromagnetic interactions in 1. The photoluminescence and lifetime of 2 in the solid state have also been studied.     

Architectural diversity of six coordination compounds based on (S)-(+)-mandelic acid and different N-donor auxiliary ligands: syntheses,structures, and luminescent properties

Six transition metal coordination compounds with H₂mand and different N-donor ligands, [Co(Hmand)₂(2,2′-bipy)]·H₂O (1), [Ni(Hmand)₂(2,2′-bipy)]·H₂O (2), [Ni(Hmand)₂(bpe)] (3), [Zn(Hmand)₂(2,4′-bipy)(H₂O)]·2H₂O (4), [Zn(Hmand)(bpe)(H₂O)]_n[(ClO₄)]_n·nH₂O (5), and [Zn(Hmand)(4,4′-bipy)(H₂O)]_n[(ClO₄)]_n (6), were synthesized under different conditions (H₂mand = (S)-(+)-mandelic acid, bpe = 1,2-di(4-pyridyl)ethane, 4,4′-bipy = 4,4′-bipyridine, 2,4′-bipy = 2,4′-bipyridine, 2,2′-bipy = 2,2′-bipyridine). Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, infrared spectra, thermogravimetric analysis, powder X-ray diffraction, and circular dichroism. Compounds 1 and 2 are isostructural (0-D structures), which are extended to supramolecular 1-D chains by hydrogen bonding. Compound 3 exhibits 1-D straight chain structures, which are further linked via hydrogen bond interactions to generate a 3-D supramolecular architecture. Compound 4 displays a discrete molecular unit. Neighboring units are further linked by hydrogen bonds and π–π interactions to form a 3-D supramolecular architecture. Compound 5 displays a 2-D undulated network, further extended into a 3-D supramolecular architecture through hydrogen bond interactions. Compound 6 possesses a 2-D sheet structure. Auxiliary ligands and counteranions play an important role in the formation of final frameworks, and the hydrogen-bonding interactions and π–π stacking interactions contributed to the formation of the diverse supramolecular architectures. Compounds 1, 2, 4, 5, and 6 crystallize in chiral space groups, with the circular dichroism spectra exhibiting positive cotton effects. Furthermore, the luminescent properties of 4–6 have been examined in the solid state at room temperature, and the different crystal structures influence emission spectra significantly.     

Plain Thin-layer Chromatography of Some Herbicides and Related Compounds on Admixture of Barium Sulfate and Calcium Sulphate in Mixed Solvents

Abstract

Some carboxylic herbicides and plant growth regulators such as benzoic acid, 4-chlorophenoxyacetic acid, cinnamic acid, 2,4-D, indole-3-acetic acid, indolepropionic acid, α-naphthalleneacetic acid, β-naphthal eneacetic acid, β-naphthoxyacetic acid, phenoxyacetic acid, TCA and 2,4,5-T have been separated on BaSO₄-CaSO₄ (1:1) coatings in mixed solvent systems.

Quantitative separations of indole-3-acetic acid (100 μg) from 50–100 μg of benzoic acid, α-naphthaleneacetic acid and 2,4,5-T have been carried out successfully.     

Determination of Phenoxy Acid Pesticides in Frog and Fish Tissues by Gas Chromatography-Mass Spectrometry

A gas chromatography-mass spectrometric GC-MS method has been developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in frog and fish tissues. After homogenization and sonication of 5 g samples, purification was achieved by a liquid phase extraction procedure using methyl-tert-butyl ether. The extract was reacted for 30 min at 80 °C with 10 % H₂SO₄ in methanol to form the corresponding methyl esters, which were simultaneously extracted with petroleum ether, and analysed by GC-MS in selected ion monitoring mode. Detection limits were 1.0 and 0.5 μg. kg^?1 for 2,4-D and 2,4,5-T respectively in tissue samples and the calibration curves showed good linearity (r ≥ 0.999). Twenty-five frog samples and forty-six fish samples from various regions in Korea were analyzed. 2,4,5-T was detected up to a maximum concentration of 16.2 μg kg^?1 in frogs and fish. The developed method may be valuable for the national monitoring project of endocrine disruptors (EDs) in biota.     

Photochemical degradation of typical halogenated herbicide 2,4-D in drinking water with UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript>/micro-aeration

UV/H₂O₂/micro-aeration is a newly developed process based on UV/H₂O₂. Halogenated pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) photochemical degradation in aqueous solution was studied under various solution conditions. The UV intensity, initial 2,4-D concentrations and solution temperature varied from 183.6 to 1048.7 μW·cm⁻², from 59.2 to 300.0 μg·L⁻¹ and from 15 to 30°C, respectively. The concentration of hydrogen peroxide (H₂O₂) and pH ranged from 0 to 50 mg·L⁻¹ and 5 to 9, and different water quality solutions (tap water, distilled water and deionized water) were examined in this study. With initial concentration of about 100 μg·L⁻¹, more than 95.6% of 2,4-D can be removed in 90 min at intensity of UV radiation of 843.9 μW·cm⁻², H₂O₂ dosage of 20 mg·L⁻¹, pH 7 and room temperature. The removal efficiency of 2,4-D by UV/H₂O₂/micro-aeration process is better than UV/H₂O₂ process. The photodecomposition of 2,4-D in aqueous solution follows pseudo-first-order kinetics. 2,4-D is greatly affected by UV irradation intensity, H₂O₂ dosage, initial 2,4-D concentration and water quality solutions, but it appears to be slightly influenced by pH and temperature. There is a linear relationship between rate constant k and UV intensity and initial H₂O₂ concentration, which indicates that higher removal capacity can be achieved by the improvement of these factors. Finally, a preliminary cost analysis reveals that UV/H₂O₂/micro-aeration process is more cost-effective than the UV/H₂O₂ process in the removal of 2,4-D from drinking water.     

Synthesis and characterization of picolinato and nicotinato cobalt(II) complexes containing tris(2-benzimidazolylmethyl)amine

Two new mononuclear cobalt(II) complexes [Co(ntb)(pic)](ClO₄) · (CH₃OH)_2.35 (1) and [Co(ntb)(nic)](ClO₄) · CH₃OH (2) were synthesized and structurally characterized, where ntb is tris(2-benzimidazolylmethyl)amine, pic is the anion of picolinic acid, and nic is the anion of nicotinic acid. The X-ray analysis indicates that the Co(II) center is six-coordinate in distorted octahedral and five-coordinate in distorted trigonal bipyramidal geometry for 1 and 2, respectively. In 1, the picolinate anion coordinates to Co(II) in a bidentate μ₂-N,O chelating mode. In 2, the nicotinate anion coordinates with Co(II) through a monodentate carboxylate oxygen. 1-D chain structures were formed by intermolecular hydrogen bonds in the two complexes and π–π interactions are important for the stabilization of the structures.     

Chinazolincarbonsäuren, 10. Mitt. Synthese von 1-Methyl-2,4-dioxo-chinazolin-3-yl-essigsäure, 2,4-Dioxo-chinazolin-1-yl-essigsäuren, 2,4-Dioxo-1,3-chinazolindiessigsäuren und deren Estern

2,4-Dioxo-quinazolin-1-yl-acetic acid esters (2) were prepared by the reaction of either 3,1-benzoxazine-2,4-diones (1) with urea in the melt or in solution or of the substituted anthranilic acid ester4 with potassium cyanate in acid solution. The anthranilamides5 with trichloromethyl chloroformate (diphosgene) gave also2. Alkaline hydrolysis of2 affords the 2,4-dioxo-quinazolin-1-yl-acetic acids (3), which were independently obtained by the sequence5 6 7. 2,4-Dioxo-1,3-quinazolinediacetic acids (11) were synthesized from1 and glycine ester. Reaction of8 with ethyl chloroformate gave9 and treatment of the latter with KOH furnished the potassium salt10, which was converted to11 by acids.Quinazoline-2,4-dione (12) with ethyl bromoacetate yielded13 and with chloroacetonitrile14. 13 was hydrolyzed to11. 14 could not be converted into11.1-Methyl-3,1-benzoxazine-2,4-dione (15) was transformed under similar conditions into 1-methyl-2,4-dioxo-quinazolin-3-yl-acetic acid (16).

     

The triflic acid-mediated cyclisation of N-benzylcinnamanilides

N-Benzylcinnamanilides cyclise with triflic acid to form 1-benzyl-4-aryl-2,4-dihydro-1H-quinolin-2-ones and 2,5-diaryl-benzazepin-3-ones. The product ratio is determined by the preferred orientation of the amide and by the electronics of the substituents. With ortho-substituted anilides, N-debenzylation also occurs to give 4-aryl-2,4-dihydro-1H-quinoline-2-ones.     

Optimizing Separation Conditions for Chlorophenoxycarboxylic Acid Herbicides in Natural and Potable Water Using Capillary Zone Electrophoresis

Chlorophenoxycarboxylic acid herbicides were separated and determined by capillary electrophoresis. An analysis of a six-component mixture containing 2,4-dichlorophenoxybutyric (2,4-DB), 2,4-dichlorophenoxypropionic (2,4-DP), 2,4,5-trichlorophenoxyacetic (2,4,5-T), 2,4-dichlorophenoxyacetic (2,4-D), and phenoxyacetic (PA) acids and 2,4-dichlorophenol (2,4-DCP), the product of their degradation in aqueous media, took no longer than 15 min. Solid-phase extraction on Diapak C-16 cartridges was used for sample preparation. The detection limits for herbicides in water samples with account for preconcentration (K = 250) were found to be 0.0005 mg/L for 2,4-DB, 2,4-DP, 2,4,5-T, and 2,4-D and 0.001 mg/L for PA. It was shown that humic acids (< 50 mg/L) do not interfere with the determination of chlorophenoxycarboxylic acids.