Determination Of Phenoxy Acid Herbicides Research Articles

Deep eutectic solvent-based emulsification liquid-liquid microextraction for the analysis of phenoxy acid herbicides in paddy field water samples.

An emulsification liquid–liquid microextraction (ELLME) method was successfully developed using phenolic-based deep eutectic solvent (DES) as an extraction solvent for the determination of phenoxy acid herbicides, 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in environmental water samples. Five different phenolics-based DESs were successfully synthesized by using phenol (DES 1), 2-chlorophenol (DES 2), 3-chlorophenol (DES 3), 4-chlorophenol (DES 4) and 3,4-dichlorophenol (DES 6) as the hydrogen-bond donor (HBD) and choline chloride as the hydrogen-bond acceptor (HBA). The DESs were mixed at 1 : 2 ratio. A homogeneous solution (clear solution) was observed upon the completion of successful synthesis. The synthesized DESs were characterized by using Fourier transform infrared and nuclear magnetic resonance (NMR). Under optimum ELLME conditions (50 µl of DES 2 as extraction solvent; 100 µl of THF as emulsifier solvent; pH 2; extraction time 5 min), enrichment factor obtained for dicamba and MCPA were 43.1 and 59.7, respectively. The limit of detection and limit of quantification obtained for dicamba were 1.66 and 5.03 µg l−1, respectively, meanwhile for MCPA were 1.69 and 5.12 µg l−1, respectively. The developed ELLME-DES method was applied on paddy field water samples, with extraction recoveries in the range of 79–91% for dicamba and 82–96% for MCPA.

Development of dispersive solid phase extraction based on dissolvable Fe3O4-layered double hydroxide for high-performance liquid chromatographic determination of phenoxy acid herbicides in water samples

Herein, magnetic nanoparticle coated with zinc-aluminum layered double hydroxide was successfully synthesized and characterized. The nanocomposite was used as an effective adsorbent to extract three phenoxy acid herbicides in water samples prior to high performance liquid chromatography-ultraviolet detection. An interesting characteristic of this sorbent is that it dissolves under acidic solution (pH < 4). As a result, the elution step was unnecessary, and no organic solvent was used in whole extraction process. Influential extraction factors such as pH of solution, amount of sorbent, type and volume of acidic solution and vortex time were optimized. The method displays low limits of detection (0.1−0.2 ng mL−1), good linearity (0.5−200 ng mL−1), acceptable precision (relative standard deviations were less than 9.3%) and accuracy (98.9–106.1%). Therefore, the method is sensitive, fast, eco-friendly, and suitable for determination of phenoxy acid herbicides in water samples.

Determination of Phenoxy Acid Herbicides in Cereals Using High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Phenoxy acid herbicide residues were found in cereals. A QuEChERS HPLC-MS/MS method was used for analysis of these herbicide residues. This technique could be used effectively for monitoring the safety of cereals.

Synchronous extraction and determination of phenoxy acid herbicides in water by on-line monolithic solid phase microextraction-high performance liquid chromatography

A C18 monolithic capillary column was utilized as the solid phase microextraction column to construct an in-tube SPME-HPLC system which was used to simultaneously extract and detect five phenoxy acid herbicides, including 2,4-dichlorophenoxyacetic acid (2,4-D), 2- (2-chloro)-phenoxy propionic acid (2,2-CPPA), 2-(3-chloro)-phenoxy propionic acid (2,3- CPPA), phenoxy propionic acid (PPA) and 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP). The operating parameters of the in-tube SPME-HPLC system, including the length of the monolithic column, the sampling flow rate, the sampling time, the elution flow rate and the elution time, had been investigated in detail. The optimized operating parameters of the in-tube SPME-HPLC system were as follow: the length of the monolithic column was 20 cm, the sampling flow rate was 0. 04 mL/min, sampling time was 13 min; the elution flow rate was 0.02 mL/min, elution time was 5 min. Under the optimized conditions, the detection limits of the five phenoxy acid herbicides were as follows: 9 µg/L for PPA, 4 µg/L for 2,2-CPPA, 4 µg/L for 2,3-CPPA, 5 µg/L for 2,4-D, 5 µg/L for 2,4-DP. Compared with the HPLC method with direct injection, the combined system showed a good enrichment factors to the analytes. The recoveries of the five phenoxy acid herbicides were between 79.0% and 98.0% (RSD ≤ 3.9%). This method was successfully used to detect the five phenoxy acid herbicides in water samples with satisfactory results.

Low-voltage electromembrane extraction combined with cyclodextrin modified capillary electrophoresis for the determination of phenoxy acid herbicides in environmental samples

In the present work, low-voltage electromembrane extraction (EME) combined with cyclodextrin (CD) modified capillary electrophoresis (CE) was applied for preconcentration and determination of some environmentally important pollutants, such as 2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-dichlorophenoxy) butanoic acid (2,4-DB), and 3,6-dichloro-2-methoxybenzoic acid (dicamba) in environmental samples. During the extraction, phenoxy acid herbicides migrated from a 4 mL aqueous sample solution through a thin layer of 1-octanol impregnated in the pores of a hollow fiber, into a 20 μL basic aqueous acceptor solution present in the lumen of the fiber. A Box–Behnken design (BBD) and response surface methodology (RSM) were used for optimization of different parameters related to extraction efficiency. The optimized extraction conditions were: 1-octanol as the supported liquid-membrane (SLM), 7 V potential difference, 24 min extraction time, donor phase pH 9.0 and acceptor phase pH 13.0. The method was reproducible so that intra and inter day RSD% were less than 4.8% by five replicate measurements for 70 ng mL−1 of each herbicide. The developed method provided linearity with correlation coefficient values higher than 0.997 over a concentration range of 30–500 ng mL−1 for 2,4-D and 2,4-DB, and 40–500 ng mL−1 for dicamba. The limits of quantitation and detection for herbicides were obtained in the range of 30–40 and 10–15 ng mL−1, respectively. Finally, the method was successfully applied for the extraction and determination of phenoxy acid herbicides from river water samples.

Determination of Phenoxy-acid Herbicides in Water with Solid Phase Microextraction Fiber Coated with Single-walled Carbon Nanotubes

By using solid phase microextraction( SPME) fiber coated with single-walled carbon nanotubes,an analytical method based on derivatization-SPME-GC-ECD method was established for the determination of 5 phenoxy-acid herbicides in water. The extraction parameters of the method were optimized,and the chemical stability of the SWCNTs fiber was investigated. The results showed that due to the inert nature of graphite,the SWCNTs fiber could be used at pH as low as 1 and the extraction efficiency of the fiber would not decline significantly after 160 extractions,showing excellent chemical stability. The linear range of the established method was 0. 5-50. 0 μg / L for Dicamba,( ±)-2-( 2,4,5-trichlorophenoxy) propionic acid( 2,4,5-TP)and trichlorophenoxy acetic acie( 2,4,5-T),1. 0-100. 0 μg / L for 2,4-dichloraphenoxy acetic acid( 2,4-D),and 5. 0-500. 0 μg / L for 4-( 2,4-dichlorophenoxy) bytyric acid( 2,4-DB). The LODs and LOQs were0. 03-0. 25 μg / L and 0. 08-0. 84 μg / L,respectively.

Fast determination of phenoxy acid herbicides in carrots and apples using liquid chromatography coupled triple quadrupole mass spectrometry

A fast, simple and inexpensive method has been developed for the analysis of phenoxy acid herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2-(4-chloro-o-tolyloxy)propionic acid (MCPP), 2-(4-aryloxyphenoxy)propionic acid (Fluazifop) and 2-(4-aryloxyphenoxy)propionic acid (Haloxyfop) in carrots and apples by liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS). The compounds were analyzed by QuEChERS (quick, easy, cheap, effective, rugged, safe) methodology without cleanup. The recoveries were performed at two spiked levels (0.05 and 0.5 mg/kg) for both matrices with six replicates for each level. The mean recoveries ranged from 70–92% for both apples and carrots. The precision of the method expressed as relative standard deviation (RSD%) was found to be in the range 3–15%. For all compounds, good linearity (r2 > 0.99) was obtained over the range of concentration from 0.05 μ g/mL to 0.5 μ g/mL, corresponding to the pesticide concentrations of 0.05 mg/kg and 0.5 mg/kg, respectively. The determination limits (LOQs) ranged from 0.01 ng/mL to 1.3 ng/mL in solvent, whereas, the LOQs calculated in matrix ranged from 0.05 ng/g to 21.0 ng/g for apples and from 0.06 ng/g to 10.2 ng/g for carrots. The developed methodology combines the advantages of both QuEChERS and LC/MS/MS producing a very rapid, sensitive and cheap method useful for the routine analytical laboratories.

SPE-LC-MS-MS Determination of Phenoxy Acid Herbicides in Surface and Ground Water

A novel method has been developed and validated for the analysis of six phenoxy acid herbicides (dicamba, 2,4-D, MCPA, dichlorprop, mecoprop and MCPB) in surface and ground waters. After solid-phase extraction on Isolute ENV+, analysis was by LC-MS-MS without using derivatization. The limits of quantitation are from 0.01 to 0.05 μg L−1. Average recoveries in method validation (spiking levels: limit of quantitation and 10 times limit of quantitation) ranged from 76.5 to 108.3%, with relative standard deviations of < 13.6%. The method was applied to real surface and ground water samples which gave average recoveries (spiking level: 0.1 μg L−1) ranging from 82.7 to 94.8%, with relative standard deviations of < 19.3%.

Automated dynamic liquid–liquid–liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection for the determination of phenoxy acid herbicides in environmental waters

Automated dynamic liquid–liquid–liquid microextraction (D-LLLME) controlled by a programmable syringe pump and combined with HPLC-UV was investigated for the extraction and determination of 5 phenoxy acid herbicides in aqueous samples. In the extraction procedure, the acceptor phase was repeatedly withdrawn into and discharged from the hollow fiber by the syringe pump. The repetitive movement of acceptor phase into and out of the hollow fiber channel facilitated the transfer of analytes into donor phase, from the organic phase held in the pore of the fiber. Parameters such as the organic solvent, concentrations of the donor and acceptor phases, plunger movement pattern, speed of agitation and ionic strength of donor phase were evaluated. Good linearity of analytes was achieved in the range of 0.5–500 ng/ml with coefficients of determination, r 2 > 0.9994. Good repeatabilities of extraction performance were obtained with relative standard deviations lower than 7.5%. The method provided up-to 490-fold enrichment within 13 min. In addition, the limits of detection (LODs) ranged from 0.1 to 0.4 ng/mL ( S/ N = 3). D-LLLME was successfully applied for the analysis of phenoxy acid herbicides from real environmental water samples.

Optimisation of a gas chromatographic–mass spectrometric method for the determination of phenoxy acid herbicides in water samples as silyl derivatives

A procedure for the determination of nine phenoxy acid herbicides in water samples using gas chromatography in combination with mass spectrometric detection is presented. Analytes were concentrated from water samples using a solid-phase extraction (SPE) polymeric sorbent, functionalised with N-vinylpyrrolidone. Compounds were eluted from the SPE cartridge using ethyl acetate and silylated with N-methyl- N-( tert-butyldimethylsilyl)trifluoracetamide (MTBSTFA). The influence of several factors on the yield of the silylation reaction and on the stability of the obtained compounds is described. Under optimal conditions derivatisation was performed at room temperature, for 5 min, using 100 μl of MTBSTFA. The obtained derivatives were stable for at least 5 days after preparation. Using a sample intake of 1000 ml, the quantification limits of the proposed method ranged from 1–4 to 4–12 ng l −1 for surface and sewage water, respectively. Recoveries between 80 and 120% were obtained depending on each particular compound and the kind of water sample considered.

Optimisation of a gas chromatographic?mass spectrometric method for the determination of phenoxy acid herbicides in water samples as silyl derivatives

A procedure for the determination of nine phenoxy acid herbicides in water samples using gas chromatography in combination with mass spectrometric detection is presented. Analytes were concentrated from water samples using a solid-phase extraction (SPE) polymeric sorbent, functionalised with N -vinylpyrrolidone. Compounds were eluted from the SPE cartridge using ethyl acetate and silylated with N -methyl- N -( tert -butyldimethylsilyl)trifluoracetamide (MTBSTFA). The influence of several factors on the yield of the silylation reaction and on the stability of the obtained compounds is described. Under optimal conditions derivatisation was performed at room temperature, for 5 min, using 100 μl of MTBSTFA. The obtained derivatives were stable for at least 5 days after preparation. Using a sample intake of 1000 ml, the quantification limits of the proposed method ranged from 1–4 to 4–12 ng l −1 for surface and sewage water, respectively. Recoveries between 80 and 120% were obtained depending on each particular compound and the kind of water sample considered.

Determination of phenoxyacid herbicides and their phenolic metabolites in surface and drinking water.

An evaluation was made of the feasibility of using reversed-phase liquid chromatography/tandem mass spectrometry with an electrospray interface (LC/ESI-MS/MS) to measure traces of phenoxyacid herbicides and their metabolites in surface and drinking water samples. The procedure involved passing 0.5 L of river and drinking water samples through a 0.5 g graphitized carbon black (GCB) extraction cartridge. Recovery was higher than 85% irrespective of the aqueous matrix in which the analytes were dissolved. A conventional 4.6-mm i.d. reversed-phase LC C-18 column operating with a mobile phase flow rate of 1 mL/min was used to chromatograph the analytes. A flow of 200 microL/min of the column effluent was diverted to the ESI source. The limits of detection (signal-to-noise ratio = 3) of the method for the pesticides considered in drinking and surface water samples are less than 0.1 ng/L for phenoxyacid herbicides, and about 5-10 ng/L for their metabolites (2,4-dichlorophenol and 4-chloro-2-methylphenol).

Determination of herbicides in soil samples by gas chromatography: optimization by the simplex method

An analytic method for the determination of phenoxy acid herbicides and 2,4-D esters in soil samples by GC-FID is described. The esterification reaction with MeOH and H 2SO 4 as catalyst has been used, optimizing experimental variables by the ‘Simplex method’. The recoveries in soil samples were between 76 and 97% with relative S.D.s between 4 and 7% ( n=4) at level of concentration of 5 and 10 μg ml −1 for phenoxy acids and 2,4-D esters, respectively.

Determination of Phenoxy Acid Herbicides in Drinking Waters by HPLC and Solid Phase Extraction

An HPLC procedure for determining phenoxy acid herbicides in waters is described. A LichroSpher RP select B octadecyl-silane analytical column and spectrophotometric detection at 230 nm were used. Adequate retention was achieved with a mobile phase containing MeOH/phosphate buffer 10−2 M pH 2.5/PnOH (50/42/8, v/v). The herbicides were isolated from water samples by using a single solid phase extraction procedure with C18 solid-phase columns. An enrichment factor of 500 is achieved. The coefficients of variation of the method were generally lower than 2.7% at 0.4 μg L−1 herbicide concentration levels. Recoveries ranged between 93 and 118%. The results obtained indicate that the proposed method is well suitable for monitoring phenoxy acid herbicides in compliance with the European Community standard for drinking water.

Determination of Phenoxy Acid Herbicides From Aqueous Samples by Improved Clean-up on Polymeric Pre-columns at High pH

An improved procedure for the determination of phenoxy acid herbicides in environmental water samples is reported. The procedure consists in solid-phase extraction (SPE) of 60 ml water samples on a polymeric pre-column at pH 2.8, a clean-up step at high pH and subsequent desorption and ion-pair LC separation at pH 8.8. The main improvements are in the basic clean-up step and in the LC eluent composition. The release of compounds which are electrostatically bound to the precolumn is favoured by a washing step with 0.1 mol l - 1 sodium hydroxide solution. As regards LC, gradient elution is applied using solvents with low buffer and ion-pairing concentrations. The detection limits for the phenoxy acids (UV detection at 232 nm) are 5–20 ng l - 1 for tap water samples. At the 0.1 µg l - 1 spiking level, the RSD is 6% (n = 7) and the recoveries are better than 83% for all analytes. The long-term reproducibility typically has RSD values of 5% (n = 7). The method was successfully tested on water samples from various origins, and the results obtained with the present on-line SPE–LC–UV procedure were found to compare well with those obtained with procedures involving SPE combined off-line with GC–MS or flow injection MS–MS.

Determination of phenoxy acid herbicides in vegetation, utilising high-resolution gel permeation chromatographic clean-up and methylation with trimethylsilydiazomethane prior to gas chromatographic analysis with mass-selective detection

A method for the determination of phenoxy acid herbicides in vegetation samples is described. Macerated samples are extracted with acetone and following filtration and acidification, the herbicides are partitioned into dichloromethane. The herbicides are then cleaned-up using high-resolution gel permeation chromatography before undergoing rapid and efficient methylation using trimethylsilyldiazomethane. The resultant methyl esters are then selectively and sensitively analyzed by gas chromatography with mass selective detection. Silanized glassware was used throughout. The method has been applied to grass samples spiked with four phenoxy acid herbicides; 2,4-D, dichlorprop, MCPA and mecoprop. Recoveries around 100% and reproducibilities of 5% ( n=4) were achieved at two spiking levels, ∼700 and ∼140 μg/kg.

Determination of phenoxyacid herbicides in drinking water at the ppt-level by liquid chromatography and on-line selective preconcentration

On-line precolumn sample handling using an anion-exchanger is applied to preconcentrate phenoxyacid herbicides in aqueous samples prior to their LC separation. Since direct percolation of large sample volumes through the ion-exchanger has to be avoided owing to the high content of inorganic anions in natural waters, a two-step preconcentration is carried out: phenoxyacids are concentrated in their neutral (acidic) form by percolation of natural samples at pH 1 first through a precolumn packed with the copolymer-based PRP-1 sorbent. Then, the PRP-1 precolumn is coupled on-line with a second one packed with the anion-exchanger and 3 ml of deionised water with 35% of acetonitrile allows the phenoxyacids to be desorbed from the PRP-1 sorbent and reconcentrated on the anion-exchanger in their ionic form. The content of the anion-exchanger is analysed on-line by coupling with a C18 analytical column and elution is made with a water-acetonitrile gradient. Detection limits in drinking water from a 500-ml sample are between 15 and 35 ng/l (ppt) and identity of phenoxyacids is reinforced by the fact that analytes are preconcentrated by the anion-exchanger. This methodology can be fully automated.

Determination of phenoxy acid herbicides by high-performance liquid chromatography and on-line enrichment

Determination of phenoxy acid herbicides by high-performance liquid chromatography and on-line enrichment

Determination of phenoxy acid herbicides by high-performance liquid chromatography and on-line enrichment

Phenoxy acid herbicides have been determined by use of high-pressure liquid chromatography (HPLC). The separation efficiency of several stationary phases like octadecyl silica and nitril silica has been estimated using different mobile phases. Regarding the necessary experimental conditions for separating phenoxy acids, the enrichment phases for on-line operation have been tested by use of column switching. The method of sample enrichment is described and the enrichment factors have been calculated.

Determination of phenoxy acid herbicides in water samples

Two HPLC methods have been developed for trace analysis of phenoxy acid herbicides in the range of 1 ppm - 1 ppb resp. 1 ppb - 20 ppt using spiked water samples. The sample preparation consists in liquid-liquid extraction followed by on line enrichment respectively solid phase preconcentration and on line enrichment. The phenoxy acids have been eluted from the enrichment column to the analytical column by means of a switching valve system. The detection was carried out by UV at 280 and 230 nm.