Nano‐structured gemini‐based supramolecular solvent for the microextraction of cyhalothrin and fenvalerate

A novel supramolecular solvent‐based microextraction followed by high‐performance liquid chromatography with ultraviolet detection method has been developed for the extraction and determination of two pyrethroid analytes, cyhalothrin and fenvalerate, in water and soil samples. The liquid–liquid‐phase separation of surfactants has been used in analytical extraction. The surfactant‐rich phase is a nano‐structured liquid, recently named as a supramolecular solvent, generated from the amphiphiles. The alkyl carboxylic acid based supramolecular solvents were introduced before. Coacervates made up of gemini surfactant, consisting of two amphiphilic moieties, were first used as solvent. The effective parameters on extraction (i.e., type of organic solvent, the amount of surfactant and volume of tetrahydrofuran, sample solution pH, salt addition, ultrasonic and centrifugation time) were investigated and optimized. Under the optimum conditions, preconcentration factors of 110 and 145 were obtained for the analytes. The linearity was 0.5–200.0 μg/L with the correlation of determination of (R²) ≥ 0.9984. The limit of detection of the method was (S/N = 3) 0.2 μg/L, and precisions in the range of 6.3–10.3% (RSDs, n = 5) were obtained. This method has been successfully applied to analyze real samples, and good recoveries in the range of 101.2–108.8% were obtained.     

Miniaturized matrix solid‐phase dispersion coupled with supramolecular solvent‐based microextraction for the determination of paraben preservatives in cream samples

An analytical method is presented for the determination of paraben preservatives in semisolid cream samples by matrix solid‐phase dispersion combined with supramolecular solvent‐based microextraction. Due to the oily and sticky nature of the sample matrix, parabens were first extracted from the samples by matrix solid‐phase dispersion using silica as sorbent material with a clean‐up performed with tetrahydrofuran in the elution step. The eluate (500 μL), 1‐decanol (120 μL), and water (4.4 mL) were then mixed in a polyethylene pipette to form supramolecular solvent. Finally, the analytes in the supramolecular solvent were separated and determined by liquid chromatography with ultraviolet detection. Under optimal extraction conditions, the extraction recoveries of the studied compounds were obtained in the range of 63–83%. The limits of detection for the analytes were between 0.03 and 0.04 μg/g. The precision of the method varied between 4.0–6.7 (intraday) and 6.2–7.9% (interday). Finally, the optimized procedure was applied to the determination of the target preservatives in a variety of cream samples (diaper rash, skin allergy, face and hand moisturizing) with satisfactory recoveries (86–102%).     

A microwave-assisted extraction method combined with magnetic ionic liquid-based dispersive liquid–liquid microextraction for the extraction of chloramine–T from fish samples prior to its determination by high-performance liquid chromatography

In the present work, a combination of microwave-assisted extraction with magnetic ionic liquid–based dispersive liquid–liquid microextraction was developed for the extraction of chloramine–T from fish samples. In this method, the sample was mixed with a hydrochloric acid solution and exposed to microwave irradiations. By doing so, chloramine–T was converted to p–toluenesulfonamide and extracted from the sample into an aqueous phase. Then, a mixture of acetonitrile (as a dispersive solvent) and magnetic ionic liquid (as an extraction solvent) was rapidly injected into the obtained solution. In the following, the magnetic solvent droplets including the extracted analytes were isolated from the aqueous solution in the presence of an external magnetic field and after diluting with acetonitrile injected into high-performance liquid chromatography equipped with a diode array detector. Under the optimum extraction conditions, high extraction recovery (78%), low limits of detection (7.2 ng/g) and quantification (23.9 ng/g), good repeatability (relative standard deviations ≤5.8 and 6.8% for intra– and inter-day precisions, respectively), and wide linear range (23.9–1000 ng/g) were obtained. Finally, various fish samples marketed in Tabriz city (East Azarbaijan, Iran) were analyzed with the suggested method.     

Development of deep eutectic solvent–based microwave-assisted extraction combined with temperature controlled ionic liquid–based liquid phase microextraction for extraction of aflatoxins from cheese samples

In this study, for the first time, a deep eutectic solvent-based microwave-assisted extraction was combined with ionic liquid–based temperature controlled liquid phase microextraction for the extraction of several aflatoxins from cheese samples. Briefly, the analytes are extracted from cheese sample (3 g) into a mixture of 1.5 mL choline chloride:ethylene glycol deep eutectic solvent and 3.5 mL deionized water by exposing to microwave irradiations for 60 s at 180 W. The liquid phase was taken and mixed with 55 μL 1-hexyl-3-methylimidazolium hexafluorophosphate. By cooling the solution in the refrigerator centrifuge, a turbid state was obtained and the analytes were extracted into the ionic liquid droplets. The analytes were determined by high-performance liquid chromatography equipped with fluorescence detector. Low limits of detection (9–23 ng kg^–1) and quantification (30–77 ng kg^–1), high extraction recovery (66%–83%), acceptable enrichment factor (40–50), and good precision (relative standard deviations ≤ 5.2%) were obtained using the offered approach. These results reveal the high extraction capability of the method for determination of aflatoxins in the cheese samples. In this method, there was no need for organic solvents and it can be considered as green extraction method.     

Sodium dodecyl sulfate sensitized switchable solvent liquid‐phase microextraction for the preconcentration of protoberberine alkaloids in Rhizoma coptidis

A sodium dodecyl sulfate sensitized switchable solvent liquid‐phase microextraction method was developed and applied to the preconcentration of active alkaloids in Rhizoma coptidis followed by high performance liquid chromatography determination. Before extraction, nonionic triethylamine was converted to its cationic form in the presence of carbon dioxide. Then, the ionic solvent carrying target analytes was once more reverted to its nonionic form by adding sodium hydroxide, as well as phase separation and analytes enrichment were realized simultaneously. Several parameters affecting the approach, such as concentration of sodium dodecyl sulfate, extraction solvent volume, sodium hydroxide concentration, sample phase pH, injection solvent type, and extraction time, were investigated and optimized. The possible microextraction mechanism of double micelle supramolecular inclusion was explored. Under the optimum conditions, the enrichment factors of four protoberberine alkaloids were from 101.8 to 152.0. The linear ranges (with r² ≥ 0.990) were 0.032–4.23, 0.031–4.33, 0.0026–10.04, and 0.0013–4.13 μg/mL for epiberberine, coptisine, palmatine, and berberine, respectively. The detection limits were in the range of 0.16–0.32 ng/mL. Satisfactory accuracies (recoveries 98.8–104.6%) and precisions (RSDs 1.9–10.9%) were also obtained. The results showed that the approach is rapid, effective, eco‐friendly, and easy‐to‐handle for the enrichment and detection of active alkaloids in Rhizoma coptidis.     

Application of in-situ formed polymer-based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid–liquid microextraction for the extraction of neonicotinoid pesticides from milk samples

An in-situ formed polymer–based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid–liquid microextraction was developed for the extraction of neonicotinoid pesticides from milk samples. The extracted analytes were determined using high-performance liquid chromatography–diode array detector. In this approach, after precipitating the proteins of milk using a zinc sulfate solution, the supernatant phase (containing sodium chloride) was transferred into another glass test tube, and a homogenous solution of polyvinylpyrrolidone and a suitable water-miscible organic solvent was rapidly injected into it. By this step, the polymer particles were re-produced and the analytes were extracted onto the sorbent surface. In the following step, the analytes were eluted with an appropriate organic solvent to use in the following solidification of floating organic droplet-based dispersive liquid–liquid microextraction step that was done to acquire the low limits of detection. Under the optimized conditions, satisfactory results consisting of low limits of detection (0.13–0.21 ng/ml) and quantification (0.43–0.70 ng/ml), high extraction recoveries (73%–85%), and enrichment factors (365–425), and good repeatability (relative standard deviations equal or less than 5.1% and 5.9% for intra- and inter-day precisions, respectively) were obtained.     

Air-assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets-liquid-liquid microextraction method for extraction of azole antifungal drugs in biological samples prior to high-performance liquid chromatography

A free dispersive method, air-assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets liquid-liquid microextraction was indicated in this study. This technique was utilized to simultaneously ascertain some azole antifungal drugs prior to high-performance liquid chromatography. In this research, a quasi-hydrophobic deep eutectic solvent was formed from tetrabutylammonium bromide and 1-dodecanol as an organic solvent at a 1:2 molar ratio. The synthesized deep decomposition in the sample solution caused in situ dispersion of extraction solvent and analytes. Air-assisted enhanced a dispersion condition in the sample solution. 1-Dodecanol as a green option was replaced with typical extraction solvents providing the advantages of a suitable freezing point near room temperature and low density. The effect of important analytical parameters on the extraction recovery of analytes was assessed. Under these optimal conditions, the limits of detection and the limits of quantitation determined were in the range of 0.5–2.8 and 1.5–9 μg/L, for water, urine and plasma samples, respectively. The intra-day and inter-day relative standard deviations (n = 5) were calculated to be 2.9–4.6 and 4.2–8.9%, respectively. The results represented the effectiveness of the developed method for the extraction and determination of analytes in biological samples.     

Nanostructured gemini‐based supramolecular solvent coupled with ultrasound‐assisted back extraction as a preconcentration step before GC–MS

Liquid‐phase microextraction based on gemini‐based supramolecular solvent was successfully applied as a preconcentration step before gas chromatography with mass spectrometry. To eliminate the interferences of gemini surfactant, the analytes were back‐extracted into an immiscible organic solvent in the presence of ultrasonic sound waves. Three phthalate esters (di‐n‐butyl‐, butylbenzyl‐, bis(2‐ethylhexyl)‐, and di‐n‐octyl phthalatic esters) were used as target analytes. The effective parameters on extraction efficiency of the target analytes (i.e., the amount of surfactant and volume of propanol as major components making up the supramolecular solvent, ionic strength, hexane volume, and ultrasound time) were investigated and optimized by a one‐variable‐at‐a‐time method. Under the optimum conditions, the preconcentration factors of the analytes were in the range of 95–182. The linear dynamic range of 0.05–200.00 μg/L with a correlation of determination of (R ²) ≥ 0.9935 was obtained. The proposed method had an excellent limit of detection (S/N = 3) of 0.01 for di‐n‐octyl and 0.02 μg/L for butylbenzyl‐ and di‐n‐butyl‐phthalatic ester. Good relative recoveries in the range of 85.7–105.2% guaranteed the accuracy of the amount of phthalates distinguished in the nonspiked samples.     

A sensitive UHPLC–MS/MS method for the simultaneous quantification of three lignans in human plasma and its application to a pharmacokinetic study

The aim of this study was to develop an analytical method to simultaneously analyze schizandrin, schizandrol B, and gomisin N lignans in human plasma using ultra high performance liquid chromatography with tandem mass spectrometry. The three lignans were separated using a mobile phase of water and acetonitrile containing 0.02% acetic acid equipped with a Kinetex C₁₈ column (2.1 mm × 50 mm, 1.7 μm). This analysis was achieved by multiple reaction monitoring mode in an electrospray interface. The mass transitions were m /z 433.1→384.0 for schizandrin, 398.8→367.8 for schizandrol B, and 400.6→299.8 for gomisin N. Liquid–liquid extraction with methyl tert‐butyl ether was used to obtain the three lignans. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma constituents. The calibration curves for the three lignans in human plasma were 0.05–50 ng/mL and displayed excellent linearity with correlation coefficients greater than 0.99. Precision for all three lignans was within 11.23%. The accuracy was 88.3–99.0% for schizandrin, 90.6–103.4% for schizandrol B, and 90.2–103.5% for gomisin N. The developed simultaneous analytical method satisfied the criteria of international guidance and could be successfully applied to the pharmacokinetic study of three lignans after oral administration of Schisandrae Fructus extract powder to humans.     

Fabrication of boronate‐decorated polyhedral oligomeric silsesquioxanes grafted cotton fiber for the selective enrichment of nucleosides in urine

Various cotton fiber based boronate‐affinity adsorbents are recently developed for the sample pretreatment of cis‐diol‐containing biomolecules, but most do not have efficient capacity due to limited binding sites on the surface of cotton fibers. To increase the density of boronate groups on the surface of cotton fiber, polyhedral oligomeric silsesquioxanes were used to modify cotton fiber to provide plentiful reactive sites for subsequent functionalization with 4‐formylphenylboronic acid. The new adsorbent showed special recognition ability towards cis‐diols and high adsorption capacity (175 μg/g for catechol, 250 μg/g for dopamine, 400 μg/g for adenosine). The in‐pipette‐tip solid‐phase extraction was investigated under different conditions, including pH and ionic strength of solution, adsorbent amount, pipette times, washing solvent, and elution solvent. The in‐pipette‐tip solid‐phase extraction coupled with high‐performance liquid chromatography was used to analyze four nucleosides in urine samples. Under the optimal extraction conditions, the detection limits were determined to be between 5.1 and 6.1 ng/mL (S/N  =  3), and the linearity ranged from 20 to 500 ng/mL for these analytes. The accuracy of the analytical method was examined by studying the relative recoveries of analytes in real urine samples with recoveries varying from 83 to 104% (RSD = 3.9–10.2%, n = 3).     

Development of a novel hollow‐fiber liquid‐phase microextraction based on oil‐in‐salt and its comparison with conventional one

A novel hollow‐fiber liquid‐phase microextraction based on oil‐in‐salt was proposed and introduced for the simultaneous extraction and enrichment of the main active compounds of hesperidin, honokiol, shikonin, magnolol, emodin, and β,β′‐dimethylacrylshikonin in a formula of Zi‐Cao‐Cheng‐Qi decoction and the single herb, Fructus Aurantii Immaturus , Cortex Magnoliae Officinalis , Radix et Rhizoma , and Lithospermum erythrorhizon , composing the formula prior to their analysis by high‐performance liquid chromatography. The results obtained by the proposed procedure were compared with those obtained by conventional hollow‐fiber liquid‐phase microextraction, and the proposed procedure mechanism was described. In the procedure, a hollow‐fiber segment was first immersed in organic solvent to fill the solvent in the fiber lumen and wall pore, and then the fiber was again immersed into sodium chloride solution to cover a thin salt membrane on the fiber wall pore filling organic solvent. Under the optimum conditions, the enrichment factors of the analytes were 0.6–109.4, linearities were 0.002–12 μg/mL with r ² ≥ 0.9950, detection limits were 0.6–12 ng/mL, respectively. The results showed that oil‐in‐salt hollow‐fiber liquid‐phase microextraction is a simple and effective sample pretreatment procedure and suitable for the simultaneous extraction and concentration of trace‐level active compounds in traditional Chinese medicine.     

Salt‐assisted dispersive liquid–liquid microextraction for enhancing the concentration of matrine alkaloids in traditional Chinese medicine and its preparations

A fast, simple, and efficient salt‐assisted dispersive liquid–liquid microextraction coupled with high‐performance liquid chromatography was developed and introduced for the simultaneous enrichment, extraction, and determination of the trace levels of matrine alkaloids (sophoridine, matrine, and sophocarpine) in Sophorae Flavescentis Radix and Composite Kushen injection. Compared with conventional dispersive liquid–liquid microextraction, the proposed method, with added salt but without dispersant and centrifuging, makes the operation simpler, greener, and leads to a higher enrichment factor. The crucial parameters affecting the enrichment factors of target analytes, such as type and volume of extraction solvent, pH of sample phase, salt concentration, volume of sample phase, and extraction time, were investigated and optimized, meanwhile, the extraction mechanism of the method was analyzed and described. Under the optimized conditions, the enrichment factors of the three matrine alkaloids were 150, 178, and 227, respectively. Good linearities (r² ≥ 0.9992) for all analytes, low limits of detection (less than 0.08 ng/mL), satisfactory precisions (2.1–12.3%), and accuracies (recoveries, 99.3–103.9%) were achieved. The experimental results showed that the approach is a simple, fast, green, eco‐friendly, and sensitive method and can be used for the preconcentration and determination of matrine alkaloids in traditional Chinese medicines and their preparations.     

Simultaneous characterization of multiple Psoraleae Fructus bioactive compounds in rat plasma by ultra‐high‐performance liquid chromatography coupled with triple quadrupole mass spectrometry for application in sex‐related differences in pharmacokinetics

A method for the simultaneous quantification of 13 bioactive compounds (psoralen, isopsoralen, isobavachin, bakuchalcone, neobabaisoflavone, bavachin, corylin, psoralidin, isobavachalcone, bavachinin, corylifol A, bavachalcone, and bakuchiol) by ultra‐high‐performance liquid chromatography coupled with triple quadrupole mass spectrometry has been developed and validated in rat plasma. Osthol was used as an internal standard and plasma samples were pretreated with one‐step liquid–liquid extraction. These analytes were separated using a gradient mobile phase system of water and acetonitrile at a flow rate of 0.2 mL/min on a reverse‐phase C18 column and analyzed in the selected multiple reactions monitoring mode. All calibration curves were linear (r > 0.9952) over the tested ranges. The intra‐ and interday accuracy and precisions of these analytes at three different concentration levels were within the acceptable limits of <15% at all concentrations. The mean recoveries of these analytes at three concentrations were more than 60.2% and the matrix effects were in the range of 85–115%. Stability studies proved that the analytes were stable under the tested conditions. The developed method was applied to evaluating the pharmacokinetic study of 13 bioactive compounds after oral administration of Psoraleae Fructus in rat of different genders. Some active compounds in Psoraleae Fructus had sex‐related pharmacokinetics.     

Determination of 19 sulfonamides residues in pork samples by combining QuEChERS with dispersive liquid–liquid microextraction followed by UHPLC–MS/MS

A new simple and rapid pretreatment method for simultaneous determination of 19 sulfonamides in pork samples was developed through combining the QuEChERS method with dispersive liquid–liquid microextraction followed by ultra‐high performance liquid chromatography with tandem mass spectrometry. The sample preparation involves extraction/partitioning with QuEChERS method followed by dispersive liquid–liquid microextraction using tetrachloroethane as extractive solvent and the acetonitrile extract as dispersive solvent that obtained by QuEChERS. The enriched tetrachloroethane organic phase by dispersive liquid–liquid microextraction was evaporated, reconstituted with 100 μL acetonitrile/water (1:9 v/v) and injected into an ultra‐high performance liquid chromatography with a mobile phase composed of acetonitrile and 0.1% v/v formic acid under gradient elution and separated using a BHE C₁₈ column. Various parameters affecting the extraction efficiency were investigated. Matrix‐matched calibration curves were established. Good linear relationships were obtained for all analytes in a range of 2.0–100 μg/kg and the limits of detection were 0.04–0.49 μg/kg. Average recoveries at three spiking levels were in the range of 78.3–106.1% with relative standard deviations less than 12.7% (n = 6). The developed method was successfully applied to determine sulfonamide residues in pork samples.     

Application of instantaneous nebulization dispersive liquid-phase microextraction combined with HPLC for the determination of chalcone and isoflavone in traditional Chinese medicines

A simple and rapid instantaneous nebulization dispersive liquid-phase microextraction method was developed, and combined with high-performance liquid chromatography for determination of the contents of seven analytes in traditional Chinese medicines. In this study, using the sprinkler device to achieve instantaneous synchronous dispersion and extraction, only one spray can rapidly achieve the concentration and enrichment of seven kinds of chalcone and isoflavones. The key factors affecting the extraction efficiency were optimized including the type and volume of extractant, the pH and salt concentration of the sample phase, and the number of dispersion. Under the optimal conditions, the enrichment factor of the target analytes ranged from 103.1 to 180.9, with good linearity and correlation coefficients above 0.9970. The limits of detection ranged from 0.02 to 0.15 ng/mL, with good accuracy (recoveries 91.1 to 108.9%) and precision (relative standard deviations 1.5–7.1%). This method has short extraction time (2 s), low organic solvent consumption and high enrichment effect, so it has a wide application prospects.     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.     

Matrix solid‐phase dispersion coupled with homogeneous ionic liquid microextraction for the determination of sulfonamides in animal tissues using high‐performance liquid chromatography

Matrix solid‐phase dispersion coupled with homogeneous ionic liquid microextraction was developed and applied to the extraction of some sulfonamides, including sulfamerazine, sulfamethazine, sulfathiazole, sulfachloropyridazine, sulfadoxine, sulfisoxazole, and sulfaphenazole, in animal tissues. High‐performance liquid chromatography was applied to the separation and determination of the target analytes. The solid sample was directly treated by matrix solid‐phase dispersion and the eluate obtained was treated by homogeneous ionic liquid microextraction. The ionic liquid was used as the extraction solvent in this method, which may result in the improvement of the recoveries of the target analytes. To avoid using organic solvent and reduce environmental pollution, water was used as the elution solvent of matrix solid‐phase dispersion. The effects of the experimental parameters on recoveries, including the type and volume of ionic liquid, type of dispersant, ratio of sample to dispersant, pH value of elution solvent, volume of elution solvent, amount of salt in eluate, amount of ion‐pairing agent (NH₄PF₆), and centrifuging time, were evaluated. When the present method was applied to the analysis of animal tissues, the recoveries of the analytes ranged from 85.4 to 118.0%, and the relative standard deviations were lower than 9.30%. The detection limits for the analytes were 4.3–13.4 μg/kg.     

Purification of lignans from Fructus Arctii using off‐line two‐dimensional supercritical fluid chromatography/reversed‐phase liquid chromatography

As a common traditional Chinese medicine, Fructus Arctii has important clinical medical values. Its main components are lignans, which are difficult to separate and analyze because of the complex composition, similar chemical structures, and close properties. In this study, an off‐line two‐dimensional supercritical fluid chromatography/reversed‐phase liquid chromatography method, as well as an effective sample pretreatment method based on hydrophilic interaction chromatography material, was developed to enrich the minor lignan fractions and obtain high‐purity compounds. In total, 12 high‐purity compounds were isolated from Fructus Arctii . Their structures were identified by using high‐resolution mass spectrometry and nuclear magnetic resonance spectroscopy, which showed that all were lignans and that most of them were isomers. The results demonstrated the effective off‐line two‐dimensional supercritical fluid chromatography/reversed‐phase liquid chromatography method for the purification of lignans from Fructus Arctii . The separation protocol established here will be beneficial for the separation of complex samples from other kinds of natural products.     

Rapid Determination of DDT and Its Metabolites in Environmental Water Samples with Mixed Ionic Liquids Dispersive Liquid–Liquid Microextraction Prior to HPLC-UV

In this paper, a novel mixed ionic liquids-dispersive liquid–liquid microextraction method was developed for rapid enrichment and determination of environmental pollutants in water samples. In this method, two kinds of ionic liquids, hydrophobic ionic liquid and hydrophilic ionic liquid, were used as extraction solvent and disperser solvent, respectively. DDT and its metabolites were used as model analytes and high-performance liquid chromatography with ultraviolet detector for the analysis. Factors that may affect the extraction recoveries, such as type and volume of extraction solvent (hydrophobic ionic liquid) and disperser solvent (hydrophilic ionic liquid), extraction time, sample pH and ionic strength, were investigated and optimized. Under the optimum conditions, the linear range was 1–100 μg L⁻¹, limits of detection could reach 0.21–0.49 μg L⁻¹, and relative standard deviation was 6.01–8.48 % (n = 7) for the analytes. Satisfactory results were achieved when the method was applied to analyze the target pollutants in environmental water samples with spiked recoveries over the range of 85.7–106.8 %.

     

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid‐phase extraction combined with dispersive liquid–liquid microextraction and high‐performance liquid chromatography

Solid‐phase extraction coupled with dispersive liquid–liquid microextraction was developed as an ultra‐preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion‐methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid‐phase extraction coupled with dispersive liquid–liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid‐phase extraction coupled with dispersive liquid–liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9–6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.