Development of multiple monolithic fiber solid‐phase microextraction and liquid chromatography–tandem mass spectrometry method for the sensitive monitoring of aminoglycosides in honey and milk samples

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples was developed using multiple monolithic fiber solid‐phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly(methacrylic acid‐co‐ethylenedimethacrylate) monolith as the extraction medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation‐exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10–0.30 and 0.23–0.59 μg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2–11%.     

Poly[(2‐(acryloyloxy) ethyl]trimethylammonium chloride‐co‐ethylene dimethacrylate monolith on‐line solid‐phase extraction coupled with liquid chromatography and tandem mass spectrometry for the fast determination of salicylic acid in foodstuffs

We report the fabrication of an anion‐exchange monolithic column in a stainless‐steel chromatographic column (10 mm × 2.1 mm i.d.) using [2‐(acryloyloxy) ethyl]trimethylammonium chloride as the monomer and ethylene dimethacrylate as the crosslinker. The prepared monolith was developed as the adsorbent for the on‐line solid‐phase extraction of salicylic acid in various animal‐origin foodstuffs combined with liquid chromatography and tandem mass spectrometry. The monolith was characterized by using Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption analysis, and elemental analysis. Potential factors affecting the on‐line solid‐phase extraction and liquid chromatography with tandem mass spectrometry analysis were studied in detail. Under the optimized conditions, the total analysis time including cleanup and liquid chromatography with tandem mass spectrometry separation was 17 min. The developed method gave the linear range of 15–750 μg/kg, detection limits (S/N = 3) of 5 μg/kg, and quantification limits (S/N = 10) of 15 μg/kg. The recoveries obtained by spiking 10, 20, and 100 μg/kg of salicylic acid in the animal‐origin food samples were in the range of 85.2–98.4%. In addition, the monolith was stable enough for 550 extraction cycles with the precision of peak area ≤11.6%.     

Loading controlled magnetic carbon dots for microwave‐assisted solid‐phase extraction: Preparation,extraction evaluation and applications in environmental aqueous samples

An adsorbent of carbon dot@poly(glycidyl methacrylate)@Fe₃O₄ nanoparticles has been developed for the microwave‐assisted magnetic solid‐phase extraction of polycyclic aromatic hydrocarbons in environmental aqueous samples prior to high‐performance liquid chromatography with UV/visible spectroscopy detection. Poly(glycidyl methacrylate) was synthesized by atom transfer radical polymerization. The chain length and amount of carbon dots attached on them can be easily controlled through changing polymerization conditions, which contributes to tunable extraction performance. The successful fabrication of the nano‐adsorbent was confirmed by transmission electronic microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and vibrating sample magnetometry. The extraction performance of the adsorbent was evaluated by using polycyclic aromatic hydrocarbons as model analytes. The key factors influencing the extraction, such as microwave power, adsorption time, desorption time and desorption solvents were investigated in detail. Under the optimal conditions, the microwave‐assisted method afforded magnetic solid‐phase extraction with short extraction time, wide dynamic linear range (0.02–200 μg/L), good linearity (R² ≥ 98.57%) and low detection limits (20–90 ng/L) for model analytes. The adsorbent was successfully applied for analyzing polycyclic aromatic hydrocarbons in environmental aqueous samples and the recoveries were in the range of 86.0–124.2%. Thus, the proposed method is a promising candidate for fast and reliable preconcentration of trace polycyclic aromatic hydrocarbons in real water samples.     

Dicationic polymeric ionic‐liquid‐based magnetic material as an adsorbent for the magnetic solid‐phase extraction of organophosphate pesticides and polycyclic aromatic hydrocarbons

Magnetic particles modified with a dicationic polymeric ionic liquid are described as a new adsorbent in magnetic solid‐phase extraction. They were obtained through the copolymerization of a 1,8‐di(3‐vinylimidazolium)octane‐based ionic liquid with vinyl‐modified SiO₂@Fe₃O₄, and were characterized by FTIR spectroscopy, X‐ray diffraction, and vibrating sample magnetometry. The modified magnetic particles are effective in the extraction of organophosphate pesticides and polycyclic aromatic hydrocarbons. Also, they can provide different extraction performance for the selected analytes including fenitrothion, parathion, fenthion, phoxim, phenanthrene, and fluoranthene, where the extraction efficiency is found to be in agreement with the hydrophobicity of analytes. Various factors influencing the extraction efficiency, such as, the amount of adsorbent, extraction, and desorption time, and type and volume of the desorption solvent, were optimized. Under the optimized conditions, a good linearity ranging from 1–100 μg/L is obtained for all analytes, except for parathion (2–200 μg/L), where the correlation coefficients varied from 0.9960 to 0.9998. The limits of detection are 0.2–0.8 μg/L, and intraday and interday relative standard deviations are 1.7–7.4% (n = 5) and 3.8–8.0% (n = 3), respectively. The magnetic solid‐phase extraction combined with high‐performance liquid chromatography can be applied for the detection of trace targets in real water samples with satisfactory relative recoveries and relative standard deviations.     

Graphene-modified TiO2 nanotube arrays as an adsorbent in micro-solid phase extraction for determination of carbamate pesticides in water samples

Graphene is a good adsorbent for organic pollutants, especially for compounds containing benzene rings. When used in TiO₂ nanotube arrays for micro-solid phase extraction (μ-SPE), the combination of graphene’s strong adsorptive properties with its good separation capabilities results in excellent sample preconcentration performance. In the present study, graphene-modified TiO₂ nanotube arrays were prepared by electrodeposition using a cyclic voltammetric reduction method. Four carbamate pesticides, including metolcarb, carbaryl, isoprocarb, and diethofencarb, were used as model analytes to validate the enrichment properties of the prepared adsorbent in μ-SPE. Factors affecting the enrichment efficiency of the μ-SPE procedure were optimized and included sample pH, elution solvents, salting-out effect, adsorption time and desorption time. Under optimal conditions, graphene-modified TiO₂ nanotube arrays exhibited excellent enrichment efficiency for carbamate pesticides. The detection limits of these carbamate pesticides ranged from 2.27 to 3.26 μg L⁻¹. The proposed method was validated using four environmental water samples, and yields of pesticides recovered from spiked test samples of the four analytes were in the range of 83.9–108.8%. These results indicate that graphene-modified TiO₂ nanotube arrays exhibit good adsorption to the target pollutants, and the method described in this work could be used as a faster and easier alternative procedure for routine analysis of carbamate pesticides in real water samples.     

Analysis of microcystins using high‐performance liquid chromatography and magnetic solid‐phase extraction with silica‐coated magnetite with cetylpyridinium chloride

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid‐phase extraction and high‐performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC‐LR was 0.001 μg/L, and the limit of quantification was 0.0028 μg/L. The limit of detection of MC‐RR was 0.001 μg/L, and the limit of quantification was 0.003 μg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid‐phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid–liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.     

Sensitive monitoring of benzoylurea insecticides in water and juice samples treated with multiple monolithic fiber solid-phase microextraction and liquid chromatographic analysis

In present study, a convenient, sensitive and environmentally friendly method for the determination of five benzoylurea insecticides (BUs) in water and juice samples was developed. To extract trace benzoylurea insecticides effectively, poly(methacrylic acid-co-ethylene dimethacrylate) monolith was prepared and used as the sorbent of multiple monolithic fiber solid-phase microextraction (MMF-SPME). The influences of preparation conditions of monolith and extraction parameters of MMF-SPME on BUs were studied thoroughly. Under the optimized conditions, the combination of MMF-SPME with high performance liquid chromatography-diode array detection (MMF-SPME-HPLC-DAD) showed expected analytical performance for target analytes. The limits of detection (S/N = 3) of the developed method were 0.026–0.075 μg L⁻¹ in water and 0.053–0.29 μg L⁻¹ in juice samples. Good linearity was obtained for analytes with the correlation coefficients (R²) above 0.99. Satisfactory repeatability and reproducibility was achieved, with relative standard deviations (RSD) of both less than 10%. Finally, the established MMF-SPME-HPLC-DAD method was successfully applied for the determination of BUs residues in juice and environmental water samples. Recoveries obtained for the determination of BUs in spiking samples ranged from 65.1% to 118%, with RSD below 10% in all cases.     

One-pot fabrication of magnetic adsorbent based on polymeric ionic liquid/aminated carbon nanotubes composite for efficient capture of synthetic auxins in complex samples prior to chromatographic analysis

Efficient enrichment is a challenging and indispensable step in the quantification of polar synthetic auxins in complex samples. In the current study, a new magnetic adsorbent based on polymeric ionic liquid/aminated carbon nanotube composite was fabricated with a one-pot precipitation copolymerization strategy and employed as the extraction phase of magnetic solid phase extraction of synthetic auxins. Various characterization techniques were utilized to inspect the morphology, structure, magnetic property, and functional groups of the prepared adsorbent. Under the optimal conditions, the obtained adsorbent displayed satisfactory capture performance towards studied auxins through multiple interactions. Adsorption studies evidenced that the adsorption procedure of the developed method towards analytes was fit for the Freundlich adsorption model and pseudo-second-order kinetics. Combining with high-performance liquid chromatography, sensitive and reliable method for the identification and quantification of trace synthetic auxins in environmental water and fruit juice samples was developed. The obtained limits of detection for water and fruit juice samples located in the ranges of 0.0059–0.013 and 0.018–0.031 μg/L, respectively. Recoveries in actual samples with different fortified contents varied from 82.2% to 117%, with satisfactory reproducibility. The results will evidence that the introduced extraction technique is a useful alternative for the entrapment of trace synthetic auxins from complex samples.     

Facile preparation of a polydopamine‐based monolith for multiple monolithic fiber solid‐phase microextraction of triazine herbicides in environmental water samples

A new multiple monolithic fiber solid‐phase microextraction using a polydopamine‐based monolith as the extraction medium is proposed. The monolith was synthesized by facile in situ copolymerization of N‐methacryldopamine and dual cross‐linkers (divinylbenzene/ethylenedimethacrylate) in the presence of N ,N‐dimethylformamide. The effect of the contents of N‐methacryldopamine and porogen in the polymerization mixture on the extraction performance was investigated thoroughly. A series of characterization studies was performed to validate the structure and properties of the monolith. The prepared multiple monolithic fibers were used for the extraction of triazine herbicides in environmental water samples. After the optimization of the extraction parameters, a convenient, sensitive, cost‐effective, and environmentally friendly method for the determination of trace triazine herbicides in water samples was developed by coupling multiple monolithic fibers solid‐phase microextraction with high‐performance liquid chromatography and diode array detection. The results indicated that the limits of detection and quantification for the target compounds were 0.031–0.14 and 0.10–0.45 μg/L, respectively. Good precision and reproducibility were obtained with the relative standard deviations below 10%. The developed method was applied to the analysis of the triazine herbicides in different water samples (lake, river, and farmland waters). The recoveries of the method were in the range between 79.6 and 117%.     

Determination of fluoroquinolones in environmental water and milk samples treated with stir cake sorptive extraction based on a boron‐rich monolith

In this study, a new stir cake sorptive extraction using a boron‐rich monolith as the adsorbent was prepared by the in situ copolymerization of vinylboronic anhydride pyridine complex and divinylbenzene. The effect of preparation parameters, including the ratio of vinylboronic anhydride pyridine complex and divinylbenzene, monomer mixture, and porogen solvent, on extraction performance was investigated thoroughly. The physicochemical properties of the adsorbent were characterized by infrared spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. Several conditions affecting the extraction efficiency were investigated in detail. Under the optimized conditions, a convenient and sensitive method for the determination of trace fluoroquinolones residues in water and milk samples was established by coupling stir cake sorptive extraction with high‐performance liquid chromatography and diode array detection. The limits of detection for the target compounds were 0.10–0.26 and 0.11–0.22 μg/L for water and milk samples, respectively. In addition, the developed method showed good linearity, repeatability, and precision. Finally, the proposed method was successfully applied for the detection of trace fluoroquinolones residues in environmental water and milk samples. Satisfactory recoveries were obtained for the determination of fluoroquinolones in spiking samples that ranged from 68.8 to 120%, with relative standard deviations below 10% in all cases.     

Metal–organic framework based in‐syringe solid‐phase extraction for the on‐site sampling of polycyclic aromatic hydrocarbons from environmental water samples

In‐syringe solid‐phase extraction is a promising sample pretreatment method for the on‐site sampling of water samples because of its outstanding advantages of portability, simple operation, short extraction time, and low cost. In this work, a novel in‐syringe solid‐phase extraction device using metal–organic frameworks as the adsorbent was fabricated for the on‐site sampling of polycyclic aromatic hydrocarbons from environmental waters. Trace polycyclic aromatic hydrocarbons were effectively extracted through the self‐made device followed by gas chromatography with mass spectrometry analysis. Owing to the excellent adsorption performance of metal–organic frameworks, the analytes could be completely adsorbed during one adsorption cycle, thus effectively shortening the extraction time. Moreover, the adsorbed analytes could remain stable on the device for at least 7 days, revealing the potential of the self‐made device for on‐site sampling of degradable compounds in remote regions. The limit of detection ranged from 0.20 to 1.9 ng/L under the optimum conditions. Satisfactory recoveries varying from 84.4 to 104.5% and relative standard deviations below 9.7% were obtained in real samples analysis. The results of this study promote the application of metal–organic frameworks in sample preparation and demonstrate the great potential of in‐syringe solid‐phase extraction for the on‐site sampling of trace contaminants in environmental waters.     

Development and validation of polymerized high internal phase emulsion monoliths coupled with HPLC and fluorescence detection for the determination of trace tetracycline antibiotics in environmental water samples

A polymerized high internal phase emulsion monolith was used as a novel sorbent for solid‐phase extraction coupled with high‐performance liquid chromatography and fluorescence detection for the determination of oxytetracycline, tetracycline, doxycycline, and chlorotetracycline in environmental water samples. The polymerized high internal phase emulsion monolithic column was prepared by the in situ polymerization of the continuous phase of a high internal phase emulsion containing glycidyl methacrylate, styrene, and divinylbenzene in pipette tips, and then functionalized with iminodiacetic acid. The resulting monolith exhibited highly interconnected porosity and large surface areas, making it an excellent candidate as an solid‐phase extraction sorbent for the enrichment of trace tetracycline antibiotics. Several factors affecting the extraction performance of polymerized high internal phase emulsion monoliths, including the pH of sample solution, the eluting solvents, the sample loading flow rate and volume, were investigated, respectively. Under the optimized conditions, the mean recoveries of oxytetracycline, tetracycline, doxycycline, and chlorotetracycline spiked in pond and farm wastewater samples ranged from 78.1 to 119.3% with relative standard deviation less than 15%. The detection limits (S/N = 3) of the proposed method were in the range of 51–137 pg/mL. This study demonstrated that the monolithic polymerized high internal phase emulsion would be promising solid‐phase extraction sorbents in the extraction and proconcentration of trace analytes from complex samples.     

Application of an optimized dispersive nanomaterial ultrasound‐assisted microextraction method for preconcentration of carbofuran and propoxur and their determination by high‐performance liquid chromatography with UV detection

An extraction method based on dispersive nanomaterial ultrasound‐assisted microextraction was used for the preconcentration of carbofuran and propoxur insecticides in water samples prior to high‐performance liquid chromatography with UV detection. ZnS:Ni nanoparticles were synthesized based on the reaction of the mixture of zinc acetate and nickel acetate with thioacetamide in aqueous media and then loaded on activated carbon (ZnS:Ni‐AC). Different methods were used for recognizing the properties of ZnS:Ni‐AC and then this nanomaterial was used for extraction of carbamate insecticide as new adsorbent. The influence of variables on the extraction method (such as amount of adsorbent (mg: NiZnS‐AC), pH and ionic strength of sample solution, vortex and ultrasonic time (min), ultrasound temperature and desorption volume (mL) was investigated by a screening 2^7–4 Plackett–Burman design. Then the significant variables were optimized by using a central composite design combined with a desirability function. At optimum conditions, this method had linear response >0.0060–10 μg/mL with detection limit 0.0015 μg/mL and relative standard deviations <5.0% (n = 3).     

Pipette‐tip solid‐phase extraction using cetyltrimethylammonium bromide enhanced molybdenum disulfide nanosheets as an efficient adsorbent for the extraction of sulfonamides in environmental water samples

Surfactant cetyltrimethylammonium bromide enhanced molybdenum disulfide was used as an adsorbent in pipette‐tip solid‐phase extraction for the pretreatment of sulfonamides in environmental water samples. The factors affecting the extraction recoveries of the analytes, including the sample pH value, amount of sorbent, type and volume of eluent solution, and salt concentration were optimized. This pipette‐tip solid‐phase extraction method demonstrated good linearity (0.05–10.0 µg/L) with a coefficient of determination of 0.9984–0.9996, limit of detection (0.2–0.4 ng/L) and limit of quantitation (0.5–1.0 ng/L), good analyte recoveries (76–91), and acceptable limit of quantitation (<10%) under the optimized conditions. These results indicated that the proposed method was a good tool for monitoring sulfonamides in environmental water samples.     

Magnetic core micelles as a nanosorbent for the efficient removal and recovery of three organophosphorus pesticides from fruit juice and environmental water samples

Sodium dodecyl sulfate coated amino‐functionalized magnetic iron oxide nanoparticles were used as an efficient adsorbent for rapid removal and preconcentration of three important organophosphorus pesticides, chlorpyrifos, diazinon and phosalone, by ultrasound‐assisted dispersive magnetic solid‐phase microextraction. Fabrication of amino‐functionalized magnetic nanoparticles was certified by characteristic analyses, including Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Affecting parameters on the removal efficiency were investigated and optimized through half‐fractional factorial design and Doehlert design, respectively. The analysis of analytes was performed by high‐performance liquid chromatography with ultraviolet detection. Under the optimum conditions, extraction recoveries for 20 ng/mL of organophosphorus pesticides were in the range of 84–97% with preconcentration factors in the range of 134–155. Replicating the experiment in above condition for five times gave the relative standard deviations <6%. The calibration curves showed high linearity in the range of 0.2–700 ng/mL and the limits of detection were in the range of 0.08–0.13 ng/mL. The proposed method was successfully applied for both removal and trace determination of these three organophosphorus pesticides in environmental water and fruit juice samples.     

Determination of trace hydroxyl polycyclic aromatic hydrocarbons in urine using graphene oxide incorporated monolith solid‐phase extraction coupled with LC‐MS/MS

The biomonitoring of hydroxy polycyclic aromatic hydrocarbons in urine, as a direct way to access multiple exposures to polycyclic aromatic hydrocarbons, has raised great concerns due to their increasing hazardous health effects on humans. Solid‐phase extraction is an effective and useful technique to preconcentrate trace analytes from biological samples. Here, we report a novel solid‐phase extraction method using a graphene oxide incorporated monolithic syringe for the determination of six hydroxy polycyclic aromatic hydrocarbons in urine coupled with liquid chromatography‐tandem mass spectrometry. The effect of graphene oxide amount, washing solvent, eluting solvent, and its volume on the extraction performance were investigated. The fabricated monoliths gave higher adsorption efficiency and capacity than the neat polymer monolith and commercial C₁₈ sorbent. Under the optimum conditions, the developed method provided the detection limits (S/N = 3) of 0.02–0.1 ng/mL and the linear ranges of 0.1–1500 ng/mL for six analytes in urine sample. The recoveries at three spiked levels ranged from 77.5 to 97.1%. Besides, the intra column‐to‐column (n = 3) and inter batch‐to‐batch (n = 3) precisions were ≤ 9.8%. The developed method was successfully applied for the determination of hydroxy polycyclic aromatic hydrocarbons in urine samples of coke oven workers.     

Boronate affinity monolithic column incorporated with graphene oxide for the in‐tube solid‐phase microextraction of glycoproteins

A poly(vinylphenylboronic acid–ethylene glycol dimethacrylate) monolithic material incorporated with graphene oxide was synthesized inside a poly(ether ether ketone) tube. This tube with boronate affinity monolith was coupled with a high‐performance liquid chromatography system through a six‐port valve to construct an online solid‐phase microextraction with high‐performance liquid chromatography system. The performance of this solid‐phase microextraction with high‐performance liquid chromatography system was demonstrated by standard glycoprotein in aqueous samples, namely, horseradish peroxidase. Some parameters that affect the extraction performance were investigated, including sampling rate, pH of sample solution, and sampling volume. Under the optimized conditions, the developed method showed high extraction efficiency toward horseradish peroxidase. The addition of graphene oxide greatly increased the extraction efficiency of boronate affinity monolith for horseradish peroxidase. The limit of detection of the proposed method was as low as 0.01 μg/mL by using ultraviolet detection. The recognition specificity was also evaluated by analyzing the mixture of bovine serum albumin (nonglycoprotein) and horseradish peroxidase. The results showed that this material could selectively extract horseradish peroxidase from the mixture, indicating its good specificity toward glycoproteins. The proposed method was further applied for analyzing rat plasma samples spiked with horseradish peroxidase. Good recovery and repeatability were obtained.     

Use of graphene coated with ZnO nanocomposites for microextraction in packed syringe of carbamate pesticides from juice samples

In this work, nanocomposites of reduced graphene oxide coated with ZnO were synthesized using a hydrothermal reduction strategy. Nanocomposite was then used as a sorbent for microextraction in a packed syringe, and its application to the extraction of carbamate pesticides from juice samples prior to high‐performance liquid chromatography detection was demonstrated. Factors affecting the enrichment efficiency of the microextraction in a packed syringe procedure were optimized, which included desorption conditions, sample pH, salting‐out effect, washing solution, and sample cycles. Under optimal conditions, the prepared materials exhibited excellent enrichment efficiency for carbamate pesticides. Good linearity existed in the concentration range of 0.5–200 ng/mL, with correlation coefficients of 0.9991–0.9997. The limits of detection of these carbamate pesticides were in the range of 0.23–1.21 ng/mL, and the average recoveries of the analytes at two spiked levels for real‐sample analysis ranged from 90.5 to 104.2% with relative standard deviations of 3.6–5.9%.     

Porous carbon derived from a metal–organic framework as an efficient adsorbent for the solid‐phase extraction of phthalate esters

A porous carbon designated as MOF‐5‐C was prepared by directly carbonizing a metal–organic framework (MOF‐5). The morphology and microstructure of MOF‐5‐C were characterized by scanning electron microscopy, N₂ adsorption, and powder X‐ray diffraction. The MOF‐5‐C retained the original porous structures of MOF‐5, and showed a high Brunauer–Emmett–Teller surface area (1808 m² g^?1) and large pore volume (3.05 cm³ g^?1). To evaluate its adsorption performance, the MOF‐5‐C was used as an adsorbent for the solid‐phase extraction of four phthalate esters from bottled water, peach juice, and soft drink samples followed by high‐performance liquid chromatographic analysis. Several parameters that could affect the extraction efficiencies were investigated. Under the optimum conditions, a good linearity was achieved in the concentration range of 0.1–50.0 ng mL^?1 for bottled water sample and 0.2–50.0 ng mL^?1 for peach juice and soft drink samples. The limits of detection of the method (S/N = 3) were 0.02 ng mL^?1 for bottled water sample, and 0.04–0.05 ng mL^?1 for peach juice and soft drink samples. The results indicated that the MOF‐5‐C exhibited an excellent adsorption capability for trace levels of phthalate esters, and it could be a promising adsorbent for the preconcentration of other organic compounds.     

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.