Determination of di‐(2‐ethylhexyl)phthalate in environmental samples by liquid chromatography coupled with mass spectrometry

Di‐(2‐ethylhexyl)phthalate (DEHP) was determined in environmental samples such as water and soil. DEHP was extracted from water samples using SPE, whereas for soils pressurized liquid extraction was applied as extraction method, using hexane/acetone (1:1, v/v) as extractant solvent. The use of HPLC coupled to MS provides the basis of the selective determination of DEHP in the analyzed samples. The extraction procedures were validated and good results were found. Recoveries were ranged from 86.0 to 99.8% with RSD lower than 18% and LODs were 0.02 mg/kg and 0.03 μg/L for soils and water, respectively. Finally, the optimized methods were applied to the analysis of real samples and DEHP was not found above the LOQ (0.05 mg/kg) in soil samples whereas it was detected in water samples at concentrations ranging between 0.19 to 0.88 μg/L.     

pH‐assisted homogeneous liquid–liquid microextraction using dialkylphosphoric acid as an extraction solvent for the determination of chlorophenols in water samples

In this study, a new pH‐assisted homogeneous liquid–liquid microextraction combined with HPLC with UV detection was developed for the determination of chlorophenols in water samples. In this approach, bis(2‐ethylhexyl) phosphate was used for the first time as the low‐density extraction solvent. In particular, 60 μL of bis(2‐ethylhexyl) phosphate was injected into the sample solution (5 mL) and dissolved completely in the sample solution while the pH was increased to 9. Afterwards, the pH of the sample solution was lowered to 1, and a cloudy solution was formed. At this stage, hydrophobic interactions between the analytes and the long double hydrocarbon chains of extraction solvent were expected to be the main forces driving extraction. A series of parameters that influence extraction were investigated systematically. Under the optimized conditions, the LODs and LOQs for the chlorophenols were 1.4–2.7 and 4.7–9.1 ng/mL, respectively. RSDs based on five replicate extraction of 100 ng/mL of each chlorophenols were <4.7% for intraday and 7.4% for interday precision. This method has been also successfully applied to analyze real water samples at two different spiked concentrations, and satisfactory recoveries were achieved.     

Preparation of magnetic molecularly imprinted polymer nanoparticles by surface imprinting by a sol–gel process for the selective and rapid removal of di‐(2‐ethylhexyl) phthalate from aqueous solution

Magnetic molecularly imprinted polymer nanoparticles for di‐(2‐ethylhexyl) phthalate were synthesized by surface imprinting technology with a sol–gel process and used for the selective and rapid adsorption and removal of di‐(2‐ethylhexyl) phthalate from aqueous solution. The prepared magnetic molecularly imprinted polymer nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and vibrating sample magnetometry. The adsorption of di‐(2‐ethylhexyl) phthalate onto the magnetic molecularly imprinted polymer was spontaneous and endothermic. The adsorption equilibrium was achieved within 1 h, the maximum adsorption capacity was 30.7 mg/g, and the adsorption process could be well described by Langmuir isotherm model and pseudo‐second‐order kinetic model. The magnetic molecularly imprinted polymer displayed a good adsorption selectivity for di‐(2‐ethylhexyl) phthalate with respect to dibutyl phthalate and di‐n‐octyl phthalate. The reusability of magnetic molecularly imprinted polymer was demonstrated for at least eight repeated cycles without significant loss in adsorption capacity. The adsorption efficiencies of the magnetic molecularly imprinted polymer toward di‐(2‐ethylhexyl) phthalate in real water samples were in the range of 98–100%. These results indicated that the prepared adsorbent could be used as an efficient and cost‐effective material for the removal of di‐(2‐ethylhexyl) phthalate from environmental water samples.     

Dispersive liquid–liquid microextraction using extraction solvent lighter than water

For the first time a dispersive liquid–liquid microextraction method on the basis of an extraction solvent lighter than water was presented in this study. Three organophosphorus pesticides (OPPs) were selected as model compounds and the proposed method was carried out for their preconcentration from water samples. In this extraction method, a mixture of cyclohexane (extraction solvent) and acetone (disperser) is rapidly injected into the aqueous sample in a special vessel (see experimental section) by syringe. Thereby, a cloudy solution is formed. In this step, the OPPs are extracted into the fine droplets of cyclohexane dispersed into aqueous phase. After centrifuging the fine droplets of cyclohexane are collected on the upper of the extraction vessel. The upper phase (0.40 μL) is injected into the gas chromatograph (GC) for separation. Analytes were detected by a flame ionization detector (FID) (for high concentrations) or MS (for low concentrations). Some important parameters, such as the kind of extraction and dispersive solvents and volume of them, extraction time, temperature, and salt amount were investigated. Under the optimum conditions, the enrichment factors (EFs) ranged from 100 to 150 and extraction recoveries varied between 68 and 105%, both of which are relatively high over those of published methods. The linear ranges were wide (10–100 000 μg/L for GC‐FID and 0.01–1 μg/L for GC‐MS) and LODs were low (3–4 μg/L for GC‐FID and 0.003 μg/L for GC‐MS). The RSDs for 100.0 μg/L of each OPP in water were in the range of 5.3–7.8% (n = 5).     

Determination of phthalate esters in bottled water using dispersive liquid–liquid microextraction coupled with GC–MS

Dispersive liquid–liquid microextraction method was developed for the determination of the amount of phthalate esters in bottled drinking water samples and dispersive liquid–liquid microextraction samples were analyzed by GC–MS. Various experimental conditions influencing the extraction were optimized. Under the optimized conditions, very good linearity was observed for all analytes in a range between 0.05 and 150 μg/L with coefficient of determination (R²) between 0.995 and 0.999. The LODs based on S/N = 3 were 0.005–0.22 μg/L. The reproducibility of dispersive liquid–liquid microextraction was evaluated. The RSDs were 1.3–5.2% (n = 3). The concentrations of phthalates were determined in bottled samples available in half shell. To understand the leaching profile of these phthalates from bottled water, bottles were exposed to direct sunlight during summer (temperature from 34–57°C) and sampled at different intervals. Result showed that the proposed dispersive liquid–liquid microextraction is suitable for rapid determination of phthalates in bottled water and di‐n‐butyl, butyl benzyl, and bis‐2‐ethylhexyl phthalate compounds leaching from bottles up to 36 h. Thereafter, degradation of phthalates was observed.     

Liquid phase microextraction‐ion exchange‐high performance thin layer chromatography for the preconcentration,separation, and determination of plasticizers in aqueous samples

Liquid phase microextraction combined with ion‐exchange‐high performance thin layer chromatography has been developed for analysis of four plasticizers in aqueous samples. After their preconcentration by liquid phase microextraction, fast separation on thin layers of inorganic ion‐exchanger stannic silicate has been developed using a mixture of toluene + ethyl acetate (10:1, v/v) as mobile phase. Consequently, densitometric quantitative determination of the plasticizers has been made at λ = 280 nm in reflection–absorption mode by Camag TLC scanner‐3. The effects of type and volume of extraction solvent, stirring rate, extraction time, and ionic strength in the microextraction method have been also evaluated and optimized. The results show that the proposed method provides enhanced accuracy, linear range, LOD, and LOQ, and is very effective for analyzing the target compounds in water samples. Under the optimized conditions, preconcentration factor of 149–279 and extraction efficiency of 31–59% have been obtained. Repeatability (5.67–7.26%) and intermediate precision (6.21–8.17%) were in acceptable range. The relative recovery obtained for each analyte in different water samples was higher than 82.3% at three fortification levels with RSD <7.9%.     

A study on separation and extraction of four main alkaloids in Macleaya cordata (Willd) R. Br. with strip dispersion hybrid liquid membrane

A technique based on strip dispersion hybrid liquid membrane was developed for the separation and extraction of four main alkaloids from fruits of Macleaya cordata (Willd) R. Br. A microporous polypropylene membrane impregnated with an organic membrane solution comprised the heart of the strip dispersion hybrid liquid membrane system. The membrane solution was made by dissolving a cationic carrier, di‐(2‐ethylhexyl) phosphoric acid in an inexpensive, less toxic membrane solvent, kerosene. The transport of alkaloids from an aqueous feed solution through the membrane to a strip dispersion phase was driven by the concentration gradient of H⁺ and facilitated by di‐(2‐ethylhexyl) phosphoric acid. The effects of the extraction time and reuse times of the membrane, the strip solution composition, the carrier concentration, the volume ratio of the aqueous strip solution to the organic membrane solution, and the flow rates of the feed solution and the strip dispersion phase on the transport of alkaloids were investigated. Under the optimal conditions, the permeability coefficients obtained for the four main alkaloids allocryptopine, protopine, sanguinarine, and chelerythrine were 1.66, 1.99, 2.98, and 3.06×10^?4 cm/s, and the transport efficiencies were as high as 68, 77, 83, and 85%, respectively.     

Extraction of lutetium(III) from aqueous solutions by employing a single fibre‐supported liquid membrane

Transport behaviour of Lu(III) across a polypropylene hollow fibre‐supported liquid membrane containing di(2‐ethylhexyl)phosphoric acid (DEHPA) in dihexyl ether as a carrier has been studied. The donor phase was LuCl₃ in the buffer solution consisting of 0.2 M sodium acetate at pH 2.5–5.0. A miniaturised system with a single hollow fibre has been operated in a batch mode. The concentration of Lu(III) was determined by indirect voltammetric method using Zn–EDTA complex. The effect of pH and volume of the donor phase, DEHPA concentration in the organic (liquid membrane) phase, the time of extraction and the content of the acceptor phase on the Lu(III) extraction and stripping behaviour was investigated. The results were discussed in terms of the pertraction and removal efficiency, the memory effect and the mean flux of Lu(III). The optimal conditions for the removal of ¹⁷⁷Lu(III) from labelled ¹⁷⁷Lu‐radiopharmaceuticals were discussed and identified. The removal efficiency of Lu(III) greater than 99% was achieved at pH of the donor phase between 3.5 and 5.0 using DEHPA concentration in the organic phase of 0.47 M and the ratio of the donor to the acceptor phase of 182.     

二（2-乙基己基）二硫代磷酸溶剂萃取铊的热动力学

在Tl₂SO₄＋Na₂SO₄＋二（2-乙基己基）二硫代磷酸＋n-C₈H₁₈＋水体系中， 测定了0.1－2.0 mol•kg^－1离子强度范围内Tl^＋ 的平衡摩尔浓度。水相中电解质Na₂SO₄ 控制溶液离子强度， 有机相中萃取剂取278.15 K至303.15 K范围内的恒定摩尔浓度。通过外推法和多项式近似得到了不同温度下的标准萃取常数K⁰，计算了萃取过程的热动力学量。     

Covalently Linked Plasticizers: Triazole Analogues of Phthalate Plasticizers Prepared by Mild Copper‐Free “Click” Reactions with Azide‐Functionalized PVC

Copper‐free azide‐alkyne click chemistry is utilized to covalently modify polyvinyl chloride (PVC). Phthalate plasticizer mimics di(2‐ethylhexyl)‐1H‐triazole‐4,5 dicarboxylate (DEHT), di(n‐butyl)‐1H‐1,2,3‐triazole‐4,5‐dicarboxylate (DBT), and dimethyl‐1H‐triazole‐4,5‐dicarboxylate (DMT) are covalently attached to PVC. DEHT, DBT, and DMT have similar chemical structures to traditional plasticizers di(2‐ethylhexyl) phthalate (DEHP), di(n‐butyl) phthalate (DBP), and dimethyl phthalate (DMP), but pose no danger of leaching from the polymer matrix and forming small endocrine disrupting chemicals. The synthesis of these covalent plasticizers is expected to be scalable, providing a viable alternative to the use of phthalates, thus mitigating dangers to human health and the environment.

     

Dispersion‐solidification liquid–liquid microextraction for volatile aromatic hydrocarbons determination: Comparison with liquid phase microextraction based on the solidification of a floating drop

Two microextraction techniques – liquid phase microextraction based on solidification of a floating organic drop (LPME‐SFO) and dispersive liquid–liquid microextraction combined with a solidification of a floating organic drop (DLLME‐SFO) – are explored for benzene, toluene, ethylbenzene and o‐xylene sampling and preconcentration. The investigation covers the effects of extraction solvent type, extraction and disperser solvents' volume, and the extraction time. For both techniques 1‐undecanol containing n‐heptane as internal standard was used as an extracting solvent. For DLLME‐SFO acetone was used as a disperser solvent. The calibration curves for both techniques and for all the analytes were linear up to 10 μg/mL, correlation coefficients were in the range 0.997–0.998, enrichment factors were from 87 for benzene to 290 for o‐xylene, detection limits were from 0.31 and 0.35 μg/L for benzene to 0.15 and 0.10 μg/L for o‐xylene for LPME‐SFO and DLLME‐SFO, respectively. Repeatabilities of the results were acceptable with RSDs up to 12%. Being comparable with LPME‐SFO in the analytical characteristics, DLLME‐SFO is superior to LPME‐SFO in the extraction time. A possibility to apply the proposed techniques for volatile aromatic hydrocarbons determination in tap water and snow was demonstrated.     

Temperature‐controlled ionic liquid dispersive liquid‐phase microextraction for the sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC‐ESI‐MS/MS

A novel dispersive liquid‐phase microextraction method without dispersive solvents has been developed for the enrichment and sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC‐ESI‐MS/MS. This method used only green solvent 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as extraction solvent and overcame the demerits of the use of toxic solvents and the instability of the suspending drop in single drop liquid‐phase microextraction. Important factors that may influence the enrichment efficiencies, such as volume of ionic liquid, pH of solutions, extraction time, centrifuging time and temperature, were systematically investigated and optimized. Under optimum conditions, linearity of the method was observed in the range of 0.1–20 μg/L for triclocarban and 0.5–100 μg/L for triclosan, respectively, with adequate correlation coefficients (R>0.9990). The proposed method has been found to have excellent detection sensitivity with LODs of 0.04 and 0.3 μg/L, and precisions of 4.7 and 6.0% (RSDs, n=5) for triclocarban and triclosan, respectively. This method has been successfully applied to analyze real water samples and satisfactory results were achieved.     

Trace Analysis of Methyl Tert‐butyl Ether in Water Samples Using New Ultrasound‐assisted Dispersive Liquid‐liquid Microextraction and Gas Chromatography‐flame Ionization Detection

In this study, simple and efficient ultrasound‐assisted dispersive liquid‐liquid microextraction combined with gas chromatography (GC) was developed for the preconcentration and determination of methyl‐tert‐butyl ether (MTBE) in water samples. One hundred microliters of benzyl alcohol was injected slowly into 10 mL home‐designed centrifuge glass vial containing an aqueous sample with 30% (w/v) of NaCl that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 μL of separated benzyl alcohol was injected into a gas chromatographic system equipped with a flame ionization detector (GC‐FID) for analysis. Several factors influencing the extraction efficiency such as the nature and volume of organic solvent, extraction temperature, ionic strength and centrifugation times were investigated and optimized. Using optimum extraction conditions a detection limit of 0.05 μg L^‐1 and a good linearity (r² = 0.998) in a calibration range of 0.1‐500 μg L^‐1 were achieved. This proposed method was successfully applied to the analysis of MTBE in tap, well and a ground water sam ple contaminated by leaking gasoline from an underground storage tank (LUST) in a gasoline service station.     

Temperature‐controlled ionic liquid‐dispersive liquid‐phase microextraction for preconcentration of chlorotoluron,diethofencarb and chlorbenzuron in water samples

This article describes a new, rapid and sensitive method for the determination of chlorotoluron, diethofencarb and chlorbenzuron from water samples with temperature‐controlled ionic liquid‐dispersive liquid‐phase microextraction. In the preconcentration procedure, ionic liquid 1‐hexyl‐3‐methylimidazolium hexafluorophosphate [C₆MIM] [PF₆] was employed as the extraction solvent. The parameters, such as volume of [C₆MIM] [PF₆], sample pH, extraction time, centrifuging time, temperature and salting‐out effect, were investigated in detail. Under the optimal extraction conditions, it has been found that three analytes had excellent LODs (S/N=3) in the range of 0.04–0.43 μg/L. The RSDs (n=6) were in the range of 1.3–4.7%. The proposed method was evaluated with lake water, tap water and melted snow water samples. The experimental results indicated that the proposed method had excellent prospect and would be widely used in the future.     

New application of chitosan‐grafted polyaniline in dispersive solid‐phase extraction for the separation and determination of phthalate esters in milk using high‐performance liquid chromatography

Chitosan‐grafted polyaniline was synthesized and applied as a sorbent for the preconcentration of phthalate esters in dispersive solid‐phase extraction. By coupling dispersive solid‐phase extraction with high‐performance liquid chromatography and response surface methodology (central composite design), a reliable, sensitive, and cost‐effective method for simultaneous determination of phthalate esters including dimethyl phthalate, di‐n‐butyl phthalate, and di(2‐ethylhexyl)phthalate was developed. The morphology of sorbent had been studied by scanning electron microscopy and its chemical structure confirmed by Fourier transform infrared spectroscopy. Under optimum condition, good linearity was observed in the range of 5.0–5000.0 ng/mL. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were 0.1–0.3 and 0.3–1 ng/mL, respectively. The relative standard deviations were less than 8.8%. Finally, this procedure was employed for extraction of trace amounts of phthalic acid esters in milk samples, the relative recoveries ranged from 82 to 103%.     

Determination of three antidepressants in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction followed by gas chromatography–flame ionization detection

This paper presents a fast and simple method for the extraction, preconcentration and determination of fluvoxamine, nortriptyline and maprotiline in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction (TA‐DLLME) followed by gas chromatography–flame ionization detection (GC‐FID). An appropriate mixture of dimethylformamide (disperser solvent), 1,1,2,2‐tetrachloroethane (extraction solvent) and acetic anhydride (derivatization agent) was rapidly injected into the heated sample. Then the solution was cooled to room temperature and cloudy solution formed was centrifuged. Finally a portion of the sedimented phase was injected into the GC‐FID. The effect of several factors affecting the performance of the method, including the selection of suitable extraction and disperser solvents and their volumes, volume of derivatization agent, temperature, salt addition, pH and centrifugation time and speed were investigated and optimized. Figures of merit of the proposed method, such as linearity (r² > 0.993), enrichment factors (820–1070), limits of detection (2–4 ng mL^?1) and quantification (8–12 ng mL^?1), and relative standard deviations (3–6%) for both intraday and interday precisions (concentration = 50 ng mL^?1) were satisfactory for determination of the selected antidepressants. Finally the method was successfully applied to determine the target pharmaceuticals in urine. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of DEHP in blood products stored in plastic bags by HPLC

Summary High-performance liquid chromatography (HPLC) was used for the routine monitoring of the plasticizers di(2-ethylhexyl) phthalate (DEHP) and tri(2-ethylhexyl) trimellitate (TOTM), in blood products. It allows easy sample clean-up, solvent extraction using Celite 545 sorbent, good recoveries and opportunity to inject large number of samples without effect on column performance. The plasticizer levels were investigated in two types of poly(vinyl chloride) (PVC) bags containing whole blood plasma, platelet concentrates (PCs) during blood taking and storage.     

Ionic‐liquid‐mediated poly(dimethylsiloxane)‐ grafted carbon nanotube fiber prepared by the sol–gel technique for the head space solid‐phase microextraction of methyl tert‐butyl ether using GC

A headspace solid‐phase microextraction method was developed for the preconcentration and extraction of methyl tert‐butyl ether. An ionic‐liquid‐mediated multiwalled carbon nanotube–poly(dimethylsiloxane) hybrid coating, which was prepared by covalent functionalization of multiwalled carbon nanotubes with hydroxyl‐terminated poly(dimethylsiloxane) using the sol–gel technique, was used as solid‐phase microextraction adsorbent. This innovative fiber exhibited a highly porous surface structure, high thermal stability (at least 320°C) and long lifespan (over 210 uses). Potential factors affecting the extraction efficiency were optimized. Under the optimum conditions, the method LOD (S/N = 3) was 0.007 ng/mL and the LOQ (S/N = 10) was 0.03 ng/mL. The calibration curve was linear in the range of 0.03–200 ng/mL. The RSDs for one fiber (repeatability, n = 5) at three different concentrations (0.05, 1, and 150 ng/mL) were 5.1, 4.2, and 4.6% and for the fibers obtained from different batches (reproducibility, n = 3) were 6.5, 5.9, and 6.3%, respectively. The developed method was successfully applied to the determination of methyl tert‐butyl ether in different real water samples on three consecutive days. The relative recoveries for the spiked samples with 0.05, 1, and 150 ng/mL were between 94–104%.     

Determination of haloperidol in biological samples with the aid of ultrasound‐assisted emulsification microextraction followed by HPLC‐DAD

A rapid and simple quantitative method for preconcentration and determination of haloperidol in biological samples was developed using ultrasound‐assisted emulsification microextraction, based on the solidification of floating organic droplet combined with HPLC‐DAD. The effects of several factors were investigated. A total of 30 μL of 1‐undecanol as an extraction solvent was injected slowly into a glass‐centrifuge tube containing 4 mL alkaline sample solution that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and the fine droplets of solvent were floated at the top of the test tube, then it was cooled in an ice bath and the solidified solvent was transferred into a conical vial, after melt, the analysis of the extract was carried out by HPLC. Under the optimal conditions, the extraction efficiencies were more than 90% and the preconcentration factors were obtained between 119–122. The LOQs were obtained between 4–8 μg/L and the calibration curves were linear within the range of 4–1000 μg/L. Finally this method was applied to the determination of haloperidol in plasma and urine samples in the range of μg/L and satisfactory results were achieved (RSDs <7%).     

Emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate and methyl methacrylate

The emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4‐butylene glycol di(2‐bromoisobutyrate). The system was mediated by copper bromide/4,4′‐dinonyl‐2,2′‐bipyridyl and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low‐temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate–2‐ethylhexyl methacrylate–methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a nonlinear least‐square method were ～0.903 and ～0.930, respectively, at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1914–1925, 2006