Chlorophenoxy Acid Herbicides Research Articles

Application of phosphonium deep eutectic solvents as extractants in ultrasound-assisted dispersive liquid-liquid microextraction for preconcentration of trace amounts of herbicides in drainage ditches waters.

In this study, an efficient preconcentration method was presented that is based on dispersive liquid-liquid microextraction taking the advantage of newly synthesized phosphonium deep eutectic solvents used as extractants and ultrasound probe as a dispersing agent. The extracts obtained were analyzed by high-performance liquid chromatography. To optimize the five most important factors for the microextraction procedure a central composite design plan was used. Under optimal conditions (140μl of extractant, 60mg of NaCl, pH=2.0, 120 s of extraction time with ultrasound probe as the dispersing agent, 16min of centrifugation for phase separation), the proposed method allowed to achieve good precision with RSD between 3.2% and 9.7% at 1.0, 5.0 and 40.0ng ml levels. The preconcentration factors were equal to 42, 39, and 41, and the limits of detection 0.128, 0.103, and 0.135ng/ml for dicamba, 2-methyl-4-chlorophenoxyacetic acid, and 2-methyl-4-chlorophenoxypropionic acid, respectively. The proposed method was successfully applied for the determination of chlorophenoxy acid herbicides in water samples from drainage ditches with a good recovery in the range of 70%-93%.

Development of a green deep eutectic solvent-based thin film solid phase microextraction technique for the preconcentration of chlorophenoxy acid herbicides in drainage ditches and river waters using a central composite design

Herbicides are chemicals commonly used for the control of the environment’s biodiversity. Many of them are soluble in water, thus they end up as water contamination. It is necessary to establish an analytical technique that can accurately measure the level of concentration of pollutants in water samples, while being time efficient, inexpensive and easy. Moreover, it is important for that technique to be green and sustainable.In this paper, the thin film solid phase microextraction (TF-SPME) technique is proposed with the use of a deep eutectic solvent (DES) as a novel sorbent. DES was a mixture of trihexyl(tetradecyl)phosphonium chloride: octadecanoic acid in a 1:2 M ratio. Stainless steel mesh was used as a support for DES sorbent. Concentrations of chlorophenoxy acid herbicides 3,6-dichloro-2-methoxybenzoic acid (DC), 2-methyl-4-chlorophenoxyacetic acid (MCPA), and 2-methyl-4-chlorophenoxypropionic acid (MCPP) were measured. To select the optimal extraction conditions, five factors such as volume of samples, amount of salt, extraction time, desorption time, and pH of samples were tested in the central composite design. According to the analysis of statistical data (Statistica), the volume and the pH of the sample were significant factors. By using DES sorbent on a mesh support, the determined herbicides were preconcentrated in samples DC 69 times, MCPA 65 times, and MCPP 71 times, respectively. Samples were taken from drainage ditches and rivers located close to farmland. The analysis was performed with the use of the HPLC-UV technique. The presence of DC and MCPA was found in two out of five samples, in amounts of 22.4 ng mL−1 and 40.3 ng mL−1. The presence of MCPP was not detected in any of the analyzed samples. Due to the high recovery (72–94 %) and precision (as RSD, 3.2–11.1 %), the developed method can be successfully used for the preconcentration and determination of chlorophenoxy acid herbicides.

Nitrogen doped Graphene Nano sheets (N−Gns) as Electrocatalyst for Electro‐Fenton Process for the Degradation of Highly Toxic Chlorophenoxy acid Herbicides from Water

AbstractFor the development of a highly active and energy‐effective electro‐Fenton process, highly efficient 2e−pathway oxygen reduction reaction electrocatalytic materials forin situelectrochemical synthesis of H2O2are extremely important. A novel nitrogen‐doped graphene nanosheets (N‐Gns) is prepared, characterized, investigated for the oxygen reduction reaction, and employed for highly toxic chlorophenoxy acid herbicides degradation in water. Herein, we report novel nitrogen‐doped graphene nano sheets (N‐Gns), which exhibit superior electrocatalytic activity and stability for oxygen reduction reaction (ORR) in acidic medium, which is utilized for Electro Fenton's reaction. The effects of operating parameters such as applied current, pH of the solution, inter‐electrode distance, ferrous ion concentration, oxygen flow rate and initial concentration of herbicides were investigated. The herbicides such as 2,4‐dichlorophenoxyacetic acid (2,4‐D), 2‐(2,4‐ dichlorophenoxy) propanoic acid (2,4‐DP), 4‐chloro‐2‐methylphenoxyacetic acid (MCPA), 2,4,5‐Trichlorophenoxyacetic acid (2,4,5‐T), 2‐(2‐methyl‐4‐chlorophenoxy) propionic acid (MCPP) were degraded by electro‐Fenton process. All the herbicides exhibited the total organic carbon removal efficiency greater than 95 % within 240 minutes. The four various places of Madurai district, Tamil Nadu, India, real water samples were collected and spiked with standard 2,4‐D solution and its degradation was studied by as‐prepared electrodes. The degradation efficiency was greater than 95 % with 300 min. It is comparatively less high than synthetic waste water (herbicides). It is due to the presence of natural organic matter in the real water samples. Hence the herbicides 2,4‐D, 2,4‐DP, 2,4,5‐T, MCPA and MCPP were successfully removed by the as‐synthesizedN doped graphene nano sheets (N‐Gns). The as‐prepared (N‐Gns) exhibits high activity and desirable stabilityand represents a potential candidate material as electro‐Fenton cathode for energy‐effective water treatment.

Solvent-loaded metal-organic framework of type MIL-101(Cr)-NH2 for the dispersive solid-phase extraction and UHPLC-MS/MS analysis of herbicides from paddy field waters.

A novel solvent-loaded dispersive solid-phase extraction (SL-DSPE) method integrated with liquid-phase microextraction (LPME) has beendeveloped by the direct loading of solvent into the pores of a metal-organic framework (MOF), MIL-101(Cr)-NH2. Despite numerous advantages of MOFs, they are usually highly hydrophobic which limits their dispersibility and therefore effective contact with the analytes in aqueous samples. To overcome this and promote its interactions with polar compounds, MIL-101(Cr) was functionalized with -NH2 and loaded with a comparatively polar organic solvent, dichloromethane. The purpose of dichloromethane was to condition the MIL-101(Cr)-NH2, promote LPME of the analytes and facilitate the re-collection of the materials after the extraction. Five chlorophenoxy acid herbicides, including 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid, were studied and determinedby ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). MIL-101(Cr)-NH2 was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and surface area measurement. Several extraction parameters were optimized, and under the most favorable conditions, the SL-DSPE-UHPLC-MS/MS method achieved enrichment factors between 25 and 66. Low limits of detection (2.66-19.7ng·L-1) and wide dynamic working ranges with good linearity (r2 ≥ 0.991) were attained for all analytes. The method was repeatable, with intra- and inter-day relative standard deviations (RSDs) below4.5 and 7.6%, respectively, for three replicate determinations. The application of SL-DSPE-UHPLC-MS/MS to paddy field waters gave satisfactory relative recoveries ranging between 80.2 and 108%, with RSDs better8.4%. Several of the CPAs were detected in these samples. Graphical abstract Schematic of the solvent-loaded dispersive solid-phase extraction procedure. By directly loading dichloromethane into the pores of MIL-101(Cr)-NH2, this method improves the extraction capability of the sorbent through the combination of solvent- and sorbent-based microextraction.

Nitrogen Doped Carbon Nanomaterial as Electrocatalyst for Oxygen Reduction Reaction in Acidic Media: To use in Electro‐Fenton

AbstractThe doped heteroatom in carbon matrices plays a crucial role in the electro‐Fenton process. Here, we investigated the electrocatalytic activities of the acetonitrile –derived (by flame synthesis) nitrogen‐doped carbon nanomaterials for the two‐electron oxygen reduction reaction (ORR) in the electro‐Fenton process, focusing on the peroxide generation and degradation of chlorophenoxy acid herbicides from contaminated water. Besides, we studied the anodic oxidation of chlorophenoxy acid herbicides from the water, and comparatively electrochemically generated OH radicals yield the higher degradation efficiency. To study the fundamental property, the linear sweep voltammetry studies of nitrogen‐doped carbon cathode material exhibits the excellent electrocatalytic activity towards 2 electron transfer oxygen reduction reaction in acidic conditions and successfully applied for the degradation of herbicides This work provides a feasible synthetic approach for scalable production of acetonitrile derived high‐performance carbon‐based ORR catalyst. The degradation results point out that, nitrogen‐doped carbon nanomaterial is one of the promising cathode materials for the degradation of organic pollutants by electro‐Fenton process

Neonicotinoids, fipronil, chlorpyrifos, carbendazim, chlorotriazines, chlorophenoxy herbicides, bentazon, and selected pesticide transformation products in surface water and drinking water from northern Vietnam

Studies on the occurrence of emerging pesticides in surface and drinking water in Vietnam are limited. In this study, lake water (n = 7), river water (n = 1), tap water (n = 46), and bottled water (n = 3) collected from Hanoi and other four provinces in northern Vietnam were analyzed for selected pesticides (including insecticides such as neonicotinoids, fipronil, and chlorpyrifos; fungicide carbendazim; herbicides such as atrazine, terbuthylazine, simazine, 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, and bentazon) and some of their degradates by liquid chromatography-tandem mass spectrometry. Carbendazim (median: 86.7 ng/L) and triazines (49.3 ng/L) were the major pesticides found in lake water samples, followed by neonicotinoids and their degradation products (15.1 ng/L), chlorpyrifos and its degradate (13.4 ng/L), fipronil and its degradates (3.76 ng/L), chlorophenoxy acid herbicides (2.10 ng/L), and bentazon (0.62 ng/L). Triazines (164 ng/L) were the major pesticides in river water. Higher concentrations (median: 39.3 ng/L; range: 1.20–127) of selected pesticides were found in tap water from Hanoi than those from four other provinces studied (5.49 ng/L; 4.73–66.8 ng/L). Bottled water samples collected from Hanoi contained lower concentrations of pesticide residues (median: 3.54 ng/L, range: 2.18–8.09) than those of tap water samples. The calculated risks from pesticide exposure through ingestion of tap water by the general populations were low. However, fipronil concentrations in lake water exceeded the benchmark value recommended for freshwater in the United States or the Netherlands. Degradation of acetamiprid into desmethyl-acetamiprid was found in lake water.

Emulsification-assisted micro-solid-phase extraction using a metal-organic framework as sorbent for the liquid chromatography-tandem mass spectrometric analysis of polar herbicides from aqueous samples

Two miniaturized sample preparation techniques, ultrasound-assisted emulsification microextraction (USAEME) and micro-solid-phase extraction (μ-SPE) have been integrated for the pre-concentration of four polar chlorophenoxy acid (CPA) herbicides from environmental aqueous samples. An metal-organic framework, MIL-101(Cr), characterized by its high porosity and large surface area, was explored as a sorbent. Despite the simplicity and convenience of μ-SPE, its use can potentially be limited by a long equilibration time, especially when applied to polar analytes. However, as demonstrated in this work, this drawback can be overcome by employing 1-octanol as a medium during the USAEME step to concentrate, and transport the polar herbicides through the polypropylene membrane of the μ-SPE device, onto the MIL-101(Cr). After μ-SPE, the herbicides were desorbed using 125 μL of organic solvent, and analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Under the most favorable conditions, wide calibration ranges with good linearity (r2 ≥ 0.995) are attained for all the herbicides. The limits of detection of the method range between 7.20 and 58.1 ng L−1 while the limits of quantification (LOQs) range between 24.0 and 194 ng L−1. The LOQs determined are lower than the guidelines set by the World Health Organization for the respective herbicides. USAEME-μ-SPE-UHPLC-MS/MS also shows good repeatability, with relative standard deviations ≤ 15.2%. Enrichment factors are between 21 and 70. The method was applied to the analysis of tap and reservoir waters, in which satisfactory relative recoveries ranging between 64.4% and 106% were obtained. The MIL-101(Cr) exhibited superior extraction capability in comparison to activated carbon and multi-walled carbon nanotubes.

Automated Mixed Matrix Membrane Microextraction Prior to Liquid Chromatography for the Determination of Chlorophenoxy Acid Herbicides in Sewage Water Samples

A new automated flow-through adsorption/desorption procedure using a multiwalled carbon nanotube immobilised mixed matrix membrane is described. The membrane consisted of 25% (w/w) multiwall carbon nanotube loading in a cellulose triacetate polymer matrix as support and was cast and embedded in a flow-through cell with a channel of an approximate length of 20 mm, a width of 2 mm, and a depth of 1.5 mm. The membrane immobilised with nanoparticles was activated using 1-octanol as a conditioning solvent. For the analyte adsorption process, 6 mL of the sample was passed through the cell at a flow rate of 0.2 mL min−1. The entrapped target analytes were then desorbed dynamically with 60 µL of 2-propanal at a flow rate of 5 µL min−1 prior to HPLC/UV analysis. The performance of the system was demonstrated for the determination of chlorinated phenoxyacetic acid herbicides in sewage water samples. Under the optimum conditions, the linearity of this method ranged from 50 to 1000 ng mL−1, with a correlation coefficient (r) ≥ 0.993 and a detection limit varying from 15 to 20 ng mL−1. Enrichment factors of up to 55 were achieved with relative recoveries of 95–99% and precision values of 6.1–7.5%.

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 1000ngg-1) and low limits of quantification (ranging from 0.10 to 0.25ngg-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).

Covalent immobilization of ionic liquid-based porous polymer onto poly(ether ether ketone) for stir bar sorptive extraction and its application in analysis of chlorophenoxy acid herbicides in soil

The application of stir bar sorptive extraction (SBSE) for polar compounds has been restricted because of less choice of suitable sorbents. In this study, an ionic liquid-based organic polymer with desired anionic exchange ability and porous structure was used for extraction of polar analytes with high extraction efficiency and capacity. For improving the workability of stir bar, the polymer was immobilized onto chemically resistant poly(ether ether ketone) (PEEK) tube by covalent modification method which including a skillful functionalization process. Afterwards, a facile detachable dumbbell-shaped structure with modified PEEK tube as jacket was constructed. Due to the excellent chemical and physical strength of PEEK material and dumbbell-shaped structure, the stir bar performed remarkable stability in the SBSE process. In addition, the detachable structure allowed the elution can be accomplished directly in the insert tube of autosampler vial with small amounts of solution, which significantly enhanced the enrichment factor and simplified the operation. After coupling with HPLC-MS/MS, the prepared organic polymer modified stir bar was applied for the analysis of three chlorophenoxy acid herbicides and showed favorable extraction efficiency with enrichment factors between 198 and 206 folds. For quantitative analysis of three chlorophenoxy acid herbicides, the method has wide linear range (0.003–10 ng/mL), good linearity (R2 ≥ 0.9958) and good reproducibility (intra-day relative standard deviation ≤ 6.16%). Furthermore, the proposed method was applied to determine chlorophenoxy acid herbicides in soil samples, the recoveries ranged from 79.4% to 97.4%, with relative standard deviation ≤ 9.3%.

A hydrogel composite prepared from alginate, an amino-functionalized metal-organic framework of type MIL-101(Cr), and magnetite nanoparticles for magnetic solid-phase extraction and UHPLC-MS/MS analysis of polar chlorophenoxy acid herbicides.

A regenerable hydrogel composite isdescribed that iscomprised of alginate, amino-functionalized metal-organic framework (MIL-101(Cr)-NH2) and magnetite nanoparticles. The composite was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, vibrating-sample magnetometry and Brunauer-Emmett-Teller measurement. The material was applied to the magnetic solid-phase extraction of six polar chlorophenoxy acid (CPA) herbicides. Specifically, the herbicides clofibric acid, 4-chlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, 2,4,5-trichlorophenoxyacetic acid and 2-(2,4,5-trichlorophenoxy)propionic acid were extracted from environmental aqueous samples and analyzed by ultra-HPLC-tandem mass spectrometry. The abundance of hydroxyl and carboxyl groups on the natural polymer renders alginate a superior hydrophilic coating. It brings the polar acidic herbicides into closer proximity to the porous metal-organic framework. When integrated with MIL-101(Cr)-NH2, the composite material combines the favorable attributes of high hydrophilicity and large adsorption capacity. An orthogonal array design matrix was employed for the optimization of the extraction parameters. Under the most favorable conditions, the method displays a wide linear response and low limits of detection (0.43-16ng⋅L-1). Precision and reproducibility (with relative standard deviations of ≤13%) are satisfactory. Enrichment factors range between 27 and 107. The composite was applied to the extraction of CPA herbicides from lake and pond water samples. A markedly improved sorbent-based extraction procedure and performance (compared to previous methods) is found. Graphical abstract Schematic of the magnetic solid-phase extraction of polar herbicides using a hydrogel composite as sorbent. The amino-functionalized MIL-101(Cr) and hydrophilic alginate work in synergy resulting in a material which possess favorable attributes of both components that are beneficial for extraction.

Poly (Octadecyl Methacrylate-Co-Trimethylolpropane Trimethacrylate) Monolithic Column for Hydrophobic in-Tube Solid-Phase Microextraction of Chlorophenoxy Acid Herbicides.

Chlorophenoxy acid herbicides (CAHs), which are widely used on cereal crops, have become an important pollution source in grains. In this work, a highly hydrophobic poly (octadecyl methacrylate-co-trimethylolpropane trimethacrylate) [poly (OMA-co-TRIM)] monolithic column has been specially prepared for hydrophobic in-tube solid-phase microextraction (SPME) of CAHs in rice grains. Due to the hydrophobicity of CAHs in acid conditions, trace CAHs could be efficiently extracted by the prepared monolith with strong hydrophobic interaction. Several factors for online hydrophobic in-tube SPME, including the length of the monolithic column, ACN and trifluoroacetic acid percentage in the sampling solution, elution volume, and elution flow rate, were investigated with respect to the extraction efficiencies of CAHs. Under the optimized conditions, the limits of detection of the four CAHs fell in the range of 0.9–2.1 μg/kg. The calibration curves provided a wide linear range of 5–600 μg/kg and showed good linearity. The recoveries of this method ranged from 87.3% to 111.6%, with relative standard deviations less than 7.3%. Using this novel, highly hydrophobic poly (OMA-co-TRIM) monolith as sorbent, a simple and sensitive online in-tube SPME-HPLC method was proposed for analysis of CAHs residue in practical samples of rice grains.

OPAC (orange peel activated carbon) derived from waste orange peel for the adsorption of chlorophenoxyacetic acid herbicides from water: Adsorption isotherm, kinetic modelling and thermodynamic studies

This study presents the orange peel activated carbon (OPAC), derived from biowaste precursor (orange peel) by single step pyrolysis method and its application for the adsorption of chlorophenoxyacetic acid herbicides from the water. The OPAC exhibited the surface area of 592.471 m2 g−1, pore volume and pore diameter of 0.242 cc g−1 and 1.301 nm respectively. The adsorption kinetics and thermodynamic equilibrium modelling for all chlorophenoxyacetic acid herbicides were investigated. The various parametric effects such as pH and temperature were evaluated. A pseudo-second-order kinetic model was well fitted for all the herbicides. The Langmuir isotherm was obeyed for all the herbicides and the maximum Langmuir capacity of 574.71 mg g−1 was achieved. The thermodynamic studies revealed that the adsorption increases with increase in temperature. The results shows that the orange peel derived carbon (OPAC) as effective and efficient adsorbent material for the removal of chlorophenoxyacid herbicides from the water.

Reliable analysis of chlorophenoxy herbicides in soil and water by magnetic solid phase extraction and liquid chromatography

There is no previous work on the determination of chlorophenoxy acid herbicides in soils. Here we analysed six chlorophenoxy acid herbicides using magnetic solid phase extraction for their preconcentration, then liquid chromatography and tandem mass spectrometry with a triple-quadrupole (LC-QqQ-MS/MS) in the multiple reaction monitoring mode. 40 mg of CoFe2O4@polypyrrole magnetic nanoparticles was added to a 30-mL sample, and vortex stirring was applied for 10 min. Analytes were desorbed using acidified methanol. The reliability of the results was validated through recovery assays, giving mean values in the 80–117 range. The intraday precision was in the 6.3–14% range, in terms of relative standard deviation.

Comparison of questionnaire data and analyzed dioxin concentrations as a measure of exposure in soft-tissue sarcoma studies

Soft-tissue sarcoma is one of the few specific tumors thought to be caused by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and specifically TCDD. Evidence is, however, based on questionnaire-based case-control studies, and on very few cancer cases in cohort studies at high occupational exposures to chlorophenols or chlorophenoxy acid herbicides with dioxin impurities. Recall bias has been suspected to influence the reporting of exposure, but this possibility has never been adequately put to test. In the present study 87 cancer patients and 308 controls answered a questionnaire asking their exposure to wood preservatives, fungicides and herbicides, and insecticides, and their PCDD/F concentrations were also measured. After matching for age and area 67–69 sarcoma patients and 153–156 controls were available for the study depending on the chemical group, 1–3 controls for each sarcoma patient. Sarcoma patients reported exposure to these chemicals significantly more often than controls did, odds ratios were 6.7 for wood preservatives (p=0.02), 16 for fungicides and herbicides (p=0.01), and 4.9 for insecticides (p=0.06). There was no association, when the analysis was based on measured PCDD/F concentrations (odds ratios close to 1). Although it is not possible to exclude the role of the main chemical as the cause with certainty, the results indicate that recall bias is very likely in previous studies. Thus the causality between contaminant PCDD/Fs and soft tissue sarcoma cannot be considered proven.

Determination of chlorophenoxy acid herbicides by using a zirconium-based metal–organic framework as special sorbent for dispersive micro-solid-phase extraction and high-performance liquid chromatography

This study reports a Zr-based MOF with 2-amino-benzenedicarboxylic acid ligand as an adsorbent for chlorophenoxy acid herbicides from biosamples.

Extraction and Derivatization of Chlorophenoxy Acid Pesticides: Performing Two DLLME with One Extracting Phase

A novel, simple and convenient method based on dispersive liquid–liquid microextraction (DLLME) and derivatization was developed and applied for isolation of a couple of selected chlorophenoxy acid herbicides from aquatic media. In the first step, analytes were extracted from acidic media into carbon tetrachloride phase using a DLLME. In following, derivatization was carried out on extracted compounds by means of methylation with an acidic methanol solution to increase their volatility and detectability in gas chromatography analysis. Finally, the derivatized analytes were re-extracted in the carbon tetrachloride phase in the second DLLME. Some important extraction parameters such as the nature and volume of the extraction solvent, disperser solvent, pH and the ionic strength were optimized. Subsequently, the developed method was validated by gas chromatography–mass spectrometry (GC–MS). Under the optimum conditions, the linearity was studied at the concentration range of 1–100 µg L−1 with a satisfactory coefficient of determination (r 2 > 0.99) for all the studied analytes. Also, the relative standard deviations (RSD %) values were from 2.5 to 4.5 % at the concentration levels of 2 and 50 µg L−1. The detection limits were found to be in the range of 0.15–0.31 µg L−1 using time-scheduled selected ion monitoring (SIM) mode. The developed method was successfully applied to the extraction and determination of chlorophenoxy acid herbicides in the river and tap water samples.

A sensitive and efficient method for the determination of 8 chlorophenoxy acid herbicides in crops by dispersive liquid–liquid microextraction and HPLC with fluorescence detection and identification by MS

A simple sample pretreatment method of dispersive liquid–liquid microextraction (DLLME) was developed for fast and efficient extraction of 8 chlorophenoxy acid herbicides.

Development and validation of thin layer chromatography method for simultaneous determination of seven chlorophenoxy and benzoic acid herbicides in water

Thin layer chromatography (TLC) densitometric method for simultaneous determination of seven chlorophenoxy and benzoic acid herbicides (2,4-D; 2,4,5-T; MCPA; 2,4-DP; MCPP; Dicamba and MCPB) in water samples was developed and validated. A mobile phase consisted of benzene−dioxane−glacial acetic acid in ratio of 45: 10: 2 and TLC silica gel 60 F254 aluminium plate were used. Detection was carried out densitometrically at 280 nm. The linearity was obtained in the range 20–200 ng per band with the correlation coefficient between the peak area and concentration for each analyte higher than 0.9976. The limits of detection and quantification were 18 and 60 ng per band, respectively. The recoveries of analyzed herbicides varied from 84.5 to 92.7%. The method can be used for routine quality analysis of chlorophenoxy and benzoic acid herbicides in natural surface and ground water samples.

Development and Validation of Thin Layer Chromatography Method for Simultaneous Determination of Seven Chlorophenoxy and Benzoic Acid Herbicides in Water

Development and Validation of Thin Layer Chromatography Method for Simultaneous Determination of Seven Chlorophenoxy and Benzoic Acid Herbicides in Water