TiO2 nanotubes： A novel solid phase extraction adsorbent for the sensitive determination of nickel in environmental water samples

A novel method was developed for the sensitive determination of nickel in environmental water samples by using TiO2 nanotubes, a new nanomaterial, as solid phase extraction absorbent. In general, TiO2 nanomaterials were often used for catalytic degradation of pollutants in environmental field, and only a very few application in environmental analytic chemistry. In present work, TiO2 nanotubes was firstly used for the enrichment of nickel and the factors would influence the preconcentration performance were optimized. Under the optimal conditions, TiO2 nanotubes exhibited its good enrichment capacity for nickel and the detection limit of the proposed method was 1 ng· mL^-1. The proposed method was validated with real water samples, and excellent results were obtained with the spiked recoveries in the range of 94.4-99.2%, respectively.     

Utilization of homogeneous liquid–liquid extraction followed by HPLC-UV as a sensitive method for the extraction and determination of phthalate esters in environmental water samples

A simple and sensitive method for the extraction of four phthalate esters including dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP) and di-n-butyl phthalate (DBP) as well as their determination in water samples was developed using homogeneous liquid–liquid extraction (HLLE) and HPLC-UV. The extraction method is based on the phase separation phenomenon by the salt addition to the ternary solvent system. The extraction parameters such as type and volume of extracting and consolute solvent, concentration of salt, pH of sample and extraction time were optimized. Under the optimal conditions (extraction solvent: 100?µL CHCl₃; consolute solvent: 2.0?mL methanol; NaCl 15% (w/v) and pH of sample: 6.5) extraction recovery was in the range of 92–102%. Linearity was observed in the range of 0.5–300?µg?L^?1 for DEP and 0.6–300?µg?L^?1 for DMP, BBP and DBP. Correlation coefficients (r ²), limits of detection (LODs) and relative standard deviations (RSDs) were in the ranges of 0.9976–0.9993, 0.18–0.25 and 1.5–4.8%, respectively. The method was successfully applied for the preconcentration and determination of these phthalate esters in the several environmental water samples.     

Biocoacervation extraction combined with dispersive solid phase extraction using a reversed-phase core–shell magnetic molecularly imprinted sorbent for 2,4-dichlorophenoxyacetic acid prior to its determination by HPLC

In this study, efficient preconcentration method has been developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) using biosorption based on microassemblies combined with core–shell magnetic molecularly imprinted polymers (mag-MIP) nanoparticles followed by high-performance liquid chromatography. The method involves three steps: (1) The bioaggregates is added to the sample. The analyte is extracted into the colloidal phase formed by aggregation of the rhamnolipid. (2) Mag-MIPs are added in order to selectively extract 2,4-D from the bioaggregate. (3) The mag-MIPs are then collected from the solution by a strong magnet placed underneath the test tube, and 2,4-D is desorbed from the surface of the mag-MIP with an acetonitrile: methanol mixture. This material has a high adsorption capacity and yields high upconcentrations, which is reusable and chemically stable. Under optimum conditions, the enrichment factor was 265. The linear dynamic range and limit of detection are 0.16–40 and 0.053 µg L^?1, respectively. The relative standard deviations for six replicate measurements are 5.2 %.     

Polyaniline/graphene oxide nanocomposite as a sorbent for extraction and determination of nicotine using headspace solid-phase microextraction and gas chromatography–flame ionization detector

A solid-phase microextraction fiber was prepared by polyaniline/graphene oxide nanocomposite as sorbent on the surface of a platinized stainless steel wire using electrospinning technique. The nanocomposite structure was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The polyaniline/graphene oxide nanocomposite fiber was used for the determination of nicotine from tobacco samples using headspace solid-phase microextraction method and gas chromatography–flame ionization detection. Influential experimental variables on the extraction efficiency of nicotine, such as extraction time and temperature, humidity and desorption conditions, were evaluated and optimized. Under the optimal experimental conditions? the limit of detection, linear dynamic range, intraday and inter-days precisions were found to be 0.01 μg g^?1, 0.05–700 µg g^?1 (R²?=?0.996), 6.9 and 8.1%, respectively. Comparison of the polyaniline/graphene oxide nanocomposite sorbent with polyaniline and commercial fibers shows longer durability, larger capacity and higher extraction efficiency. The polyaniline/graphene oxide nanocomposite fiber was successfully applied for the determination of nicotine in tobacco samples.     

An ionic liquid-based sorbent for solid phase extraction of trace iron(Ш) from biological and natural water samples

A new ionic liquid modified silica gel sorbent was prepared from the reaction of active silica gel with N-3-(-3-triethoxysilylepropyl)-3-methylimidazolium chloride ([(TESP)MIm]Cl). This sorbent was exploited as solid phase extractant for separation and preconcentration of metal ions prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). It was found that it can selectively adsorb Fe(Ш). Identification of the surface modification was performed on the basis of FT-IR. Experimental conditions for effective adsorption of trace Fe(Ш) were optimised using both batch and column procedures. At pH 3, Fe(Ш) could be quantitatively adsorbed and completely eluted by using 2?mL of 0.1?mol?L^?1 of HCl. 150?mL of sample solution was adopted as the maximum sample volume and a high enrichment factor of 75 was obtained. Most common coexisting ions did not interfere with the separation and preconcentration of Fe(Ш) at optimal conditions. The maximum static adsorption capacity of the sorbent was 37.0?mg?g^?1. The detection limit of the present method was 0.48?µg?L^?1, and the relative standard deviation (R. S. D.) was lower than 1.7%. The method was successfully applied to the preconcentration of trace Fe(Ш) in biological and natural water samples with satisfactory results.     

Carbon nanotubes as the sorbent for integrating μ-solid phase extraction within the needle of a syringe

In this research we report the implementation of micro-solid-phase extraction (μ-SPE) in the needle of a syringe for integrating sampling, analyte enrichment and sample introduction into a single device. Both single- and multi-walled carbon nanotubes (CNTs) were explored as high performance sorbents for μ-SPE in packed and self assembled formats. The need for such a sorbent was critical because the needle probe could hold only a small amount of material (around 300 μg). Conventional C-18 and self-assembled CNTs were found to be ineffective with enrichment factors less than one. However, packed beds of CNTs were found to be excellent sorbent phases, where high extraction efficiencies (as high as 27%) as well as enrichment factors (close to 7) could be achieved. The overall method showed excellent linearity, reproducibility, and low method detection limit (0.1–3 ng/mL for MWNTs). The sorption on CNTs followed Freundlich isotherms, and the functionalized CNTs were more effective for enriching the polar compounds.     

Application of Nylon6/Polypyrrole core–shell nanofibres mat as solid-phase extraction adsorbent for the determination of atrazine in environmental water samples

A novel solid-phase extraction (SPE) system, based on a new sorbent of Nylon6/Polypyrrole (PA6/PPy) core–shell nanofibres mat and a new packing format of SPE disks, is presented in this paper. A series of related parameters that may affect the efficiency, such as the kind of eluent and its volume, the amount of nanofibres mat, ionic strength, pH of the sample, flow rate of the sample and volume of the sample, have been investigated systematically. Under the optimised conditions, the target analyte in 10 mL water samples can be completely extracted by a 3.0 mg PA6/PPy nanofibres mat and easily eluted by 400 µL acetonitrile. Around 20 µL elution was injected directly to HPLC-UV for determination, without further concentration. Besides, the nanofibres mat could be repeatedly used up to six cycles. Satisfactory linearity was achieved in the range of 0.1–40.0 ng/mL with a correlation coefficient of 0.9999. The limit of detection (LOD) (3 S/N) was 0.03 ng/mL, which could meet the determination requirements of atrazine as per the European Union legislation, US. Safe Drinking Water Act and the State Environmental Protection Administration of China. The simple, effective and economic method was proposed for the determination of atrazine in environmental water at trace level. The recoveries ranged from 94.73 to 114.92%, with relative standard deviations (RSDs) of 2.5–4.2%, and were obtained from tap water and lake water samples with atrazine at 2.0 ng/mL, suggesting the actual feasibility of the proposed method in environmental water samples.     

Polydimethylsiloxane/graphene oxide/β-cyclodextrin sponge as a solid-phase extraction sorbent coupled with gas chromatography-mass spectrometry for rapid adsorption and sensitive determination of lavender essential oil

An adsorbent polydimethylsiloxane/graphene oxide/β-cyclodextrin sponge, which possessed the merits of high surface area, chemical stability, environment friendly, and excellent extraction capacity, was successfully fabricated. Based on the advantages, a novel microwave-assisted headspace solid-phase extraction method for lavender essential oil using polydimethylsiloxane/graphene oxide/β-cyclodextrin sponge as adsorbents was developed in this study. Various experimental parameters were studied. The optimal extraction conditions were as follows: 1 mg/mL as dopamine solution concentration, graphene oxide dosages of 30 mg, microwave power of 700 W, microwave irradiation time of 10 min, and desorption solvent of n-hexane. Under the optimal extraction condition, linearities ranging from 10 to 800 ng were achieved for six representative compounds with a correlation coefficients value of >0.99. The intra-day and inter-day precisions were in the ranges of 0.40–1.56 and 0.67–2.56%, respectively. Finally, the proposed technique was applied to analyze essential oil constituents in 14 samples of three lavender varieties, and 48 compounds were identified. Lavender varieties were distinguished using principal component analysis and partial least squares discriminant analysis. The results showed that the method developed in this study is a novel, simple, and sensitive method for the determination of essential oil in complex plant samples.     

β-Cyclodextrin-grafted magnetic graphene oxide nanocomposites in ultrasound-assisted dispersive magnetic solid-phase extraction for simultaneous preconcentration of lead and cadmium ions

Research on Chemical Intermediates - This article presents an ultrasound-assisted dispersive magnetic solid-phase extraction method (USA-DMSPE) to preconcentration Cd(II) and Pb(II) simultaneously....     

On-line solid phase extraction-liquid chromatography–mass spectrometry for trace determination of nerve agent degradation products in water samples

Three primary nerve agent degradation products (ethyl-, isopropyl- and pinacolyl methylphosphonic acid) have been determined in water samples using on-line solid phase extraction-liquid chromatography and mass spectrometry (SPE-LC–MS) with electrospray ionisation. Porous graphitic carbon was employed for analyte enrichment followed by hydrophilic interaction chromatography. Diethylphosphate was applied as internal standard for quantitative determination of the alkyl methylphosphonic acids (AMPAs). By treating the samples with strong cation-exhange columns on Ba, Ag and H form, the major inorganic anions in water were removed by precipitation prior to the SPE-LC–MS determination. The AMPAs could be determined in tap water with limits of detection of 0.01–0.07 μg L⁻¹ with the [M−H]⁻ ions extracted at an accuracy of ±5 mDa. The within and between assay precisions at analyte concentrations of 5 μg L⁻¹ were 2–3%, and 5–9% relative standard deviation, respectively. The developed method was employed for determination of the AMPAs in three natural waters and a simulated waste water sample, spiked at 5 μg L⁻¹. Recoveries of ethyl-, isopropyl- and pinacolyl methylphosphonic acid were 80–91%, 92–103% and 99–106%, respectively, proving the applicability of the technique for natural waters of various origins.     

Separation and extraction of Co(II) using magnetic chitosan nanoparticles grafted with β-cyclodextrin and determination by FAAS

A novel and selective method for the fast determination of trace amounts of Co(II) ions in water samples has been developed. The procedure is based on the selective sorption of Co(II) ions using magnetic chitosan nanoparticles grafted with β-cyclodextrin at different pH followed by elution with organic eluents and determination by atomic absorption spectrometry The preconcentration factor was 100 (1 mL elution volume) for a 100 mL sample volume. The limit of detection of the proposed method is 1.0 ng mL^?1. The maximum sorption capacity of sorbent under optimum conditions has been found to be 5 mg of Co per gram of sorbent. The relative standard deviation under optimum conditions was 3.0% (n = 10). Accuracy and applicability of the method was estimated using test samples of natural and model water with different amounts of Co(II).     

Hybrid organic–inorganic silica monolith with hydrophobic/strong cation-exchange functional groups as a sorbent for micro-solid phase extraction

A hybrid organic–inorganic silica monolith with hydrophobic and strong cation-exchange functional groups was prepared and used as a sorbent for micro-solid phase extraction (micro-SPE). The hybrid silica monolith functionalized with octyl and thiol groups was conveniently synthesized by hydrolysis and polycondensation of a mixture of tetraethoxysilane (TEOS), n-octyltriethoxysilane (C8-TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) via a two-step catalytic sol–gel process. Due to the favorable chemical reactivity of mercapto pendant moieties, the obtained hybrid monolith was oxidized using hydrogen peroxide (30%, w/w) to yield sulfonic acid groups, which provided strong cation-exchange sites. The obtained hybrid monolith was characterized by diffused infrared spectroscopy, elemental analysis, scanning electron microscopy and mercury intrusion porosimetry. The results show that the resulting monolith contains much higher carbon (31.6%) and sulfur (4.8%) contents than traditionally bonded silica materials. The extraction performance of the hybrid monolith was evaluated using sulfonamides as testing analytes by micro-SPE on-line coupled to HPLC. The results show that the hybrid monolith with hydrophobic and strong cation-exchange functional groups exhibits high extraction efficiency towards the testing analytes. The column-to-column RSD values were 1.3–9.8% for the extraction of SAs investigated. The extraction performance of the hybrid silica monolith remained practically unchanged after treated with acid (pH 1.0) and basic solutions (pH 10.5). Finally, the application of the hybrid monolith was demonstrated by micro-SPE of sulfonamide residues from milk followed by HPLC–UV analysis. The limits of detection (S/N = 3) for eight SAs were found to be 1.0–3.0 ng/mL in milk. The recoveries of eight SAs spiked in milk sample ranged from 80.2% to 115.6%, with relative standard deviations less than 11.8%.     

A chitosan–polypyrrole magnetic nanocomposite as μ-sorbent for isolation of naproxen

An extracting medium based on chitosan–polypyrrole (CS–PPy) magnetic nanocomposite was synthesized by chemical polymerization of pyrrole at the presence of chitosan magnetic nanoparticles (CS-MNPs) for micro-solid phase extraction. In this work, magnetic nanoparticles, the modified CS-MNPs and different types of CS–PPy magnetic nanocomposites were synthesized. Extraction efficiency of the CS–PPy magnetic nanocomposite was compared with the CS-MNPs and Fe₃O₄ nanoparticles for the determination of naproxen in aqueous samples, via quantification by spectrofluorimetry. The scanning electron microscopy images obtained from all the prepared nanocomposites revealed that the CS–PPy magnetic nanocomposite possess more porous structure. Among different synthesized magnetic nanocomposites, CS–PPy magnetic nanocomposite showed a prominent efficiency. Influencing parameters on the morphology of CS–PPy magnetic nanocomposite such as weight ratio of components was also assayed. In addition, effects of different parameters influencing the extraction efficiency of naproxen including desorption solvent, desorption time, amount of sorbent, ionic strength, sample pH and extraction time were investigated and optimized. Under the optimum condition, a linear calibration curve in the range of 0.04–10 μg mL⁻¹ (R² = 0.9996) was obtained. The limits of detection (3S_b) and limits of quantification (10S_b) of the method were 0.015 and 0.04 μg mL⁻¹ (n = 3), respectively. The relative standard deviation for water sample spiked with 0.1 μg mL⁻¹ of naproxen was 3% (n = 5) and the absolute recovery was 92%. The applicability of method was extended to the determination of naproxen in tap water, human urine and plasma samples. The relative recovery percentages for these samples were in the range of 56–99%.     

Membrane-assisted solvent extraction coupled to large volume injection–gas chromatography–mass spectrometry for the determination of a variety of endocrine disrupting compounds in environmental water samples

Membrane-assisted solvent extraction coupled to large volume injection in a programmable temperature vaporisation injector using gas chromatography–mass spectrometry analysis was optimised for the simultaneous determination of a variety of endocrine disrupting compounds in environmental water samples (estuarine, river and wastewater). Among the analytes studied, certain hormones, alkylphenols and bisphenol A were included. The nature of membranes, extraction solvent, extraction temperature, solvent volume, extraction time, ionic strength and methanol addition were evaluated during the optimisation of the extraction. Matrix effects during the extraction step were studied in different environmental water samples: estuarine water, river water and wastewater (influent and effluent). Strong matrix effects were observed for most of the compounds in influent and effluent samples. Different approaches were studied in order to correct or minimise matrix effects, which included the use of deuterated analogues, matrix-matched calibration, standard addition calibration, dilution of the sample and clean-up of the extract using solid-phase extraction (SPE). The use of deuterated analogues corrected satisfactorily matrix effect for estuarine and effluent samples for most of the compounds. However, in the case of influent samples, standard addition calibration and dilution of the sample were the best approaches. The SPE clean-up provided similar recoveries to those obtained after correction with the corresponding deuterated analogue but better chromatographic signal was obtained in the case of effluent samples. Method detection limits in the 5–54 ng L⁻¹ range and precision, calculated as relative standard deviation, in the 2–25% range were obtained.     

SBA-15/Metformin as a novel sorbent combined with surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) for highly sensitive determination of Pb,Cd and Ni in food and environmental samples

This paper established a new, rapid and sensitive method for the ultra-trace determination of lead, cadmium and nickel in food and environmental samples preconcentrated by dispersive solid-phase extraction (DSPE) combined with surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) prior to graphite furnace atomic absorption spectrometry. SBA-15/Met was synthesized and used as a new efficient sorbent for the extraction of metal ions in DSPE. It was characterized by TEM and TGA techniques. After DSPE step, stripped metal elements were complexed with dithizone, and then, the complexes were extracted into carbon tetrachloride by using SA-DLLME. A conventional nonionic surfactant, triton X-100 was used as a disperser agent. Under the optimized conditions, the limit of quantifications was found to be 2.5 ng L^?1 for Pb²⁺, Cd²⁺ and 5.0 ng L^?1 for Ni²⁺. The limits of detection were 1.5 ng L^?1 for Ni²⁺ and 0.75 ng L^?1 for Pb²⁺ and Cd²⁺, with enrichment factor of 1650. The optimized method exhibited a good precision level with relative standard deviations (RSDs%) values of 4.9, 5.2 and 5.0% for 1 μg L^?1 Pb²⁺, Cd²⁺ and Ni²⁺, respectively (n = 7). Application of the proposed method to the analysis of fish-certified reference material produced results that were in good agreement with the certified values.     

In-sample acetylation-non-porous membrane-assisted liquid–liquid extraction for the determination of parabens and triclosan in water samples

A procedure for the determination of seven parabens (esters of 4-hydroxybenzoic acid), including the distinction between branched and linear isomers of propyl- and butyl-parabens and triclosan in water samples, was developed and evaluated. The procedure includes in-sample acetylation-non-porous membrane-assisted liquid–liquid extraction and large volume injection–gas chromatography–ion trap–tandem mass spectrometry. Different derivatisation strategies were considered, i.e. post-extraction silylation with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide and in situ acylation with acetic anhydride (Ac₂O) and isobutylchloroformate. Moreover, acceptor solvent and the basic catalyser of the acylation reaction were investigated. Thus, in situ derivatisation with Ac₂O and potassium hydrogenphosphate (as basic catalyser) was selected. Potassium hydrogenphosphate overcomes some drawbacks of other basic catalysers, e.g. toxicity and bubble formation, while leads to higher responses. Subsequently, other experimental variables affecting derivatisation–extraction yield such as pre-stirring time, salt addition and volume of Ac₂O were optimised by an experimental design approach. Under optimised conditions, the proposed method achieved detection limits from 0.1 to 1.4 ng L⁻¹ for a sample volume of 18 mL and extraction efficiencies, estimated by comparison with liquid–liquid extraction, between 46% (for methyl- and ethyl-parabens) and 110% (for benzylparaben). The reported sample preparation approach is free of matrix effects for parabens but affected for triclosan with a reduction of ≈ 40% when wastewater samples are analysed; therefore, both internal and external calibration can be used as quantification techniques for parabens, but internal standard calibration is mandatory for triclosan. The application of the method to real samples revealed the presence of these compounds in raw wastewater at concentrations up to 26 ng mL⁻¹, the prevalence of the linear isomer of propylparaben (n-PrP), and the coexistence of the two isomers of butylparaben (i-BuP and n-BuP) at similar levels.     

Using bamboo charcoal as solid-phase extraction adsorbent for the ultratrace-level determination of perfluorooctanoic acid in water samples by high-performance liquid chromatography–mass spectrometry

In recent years, bamboo charcoal, a new kind of material with special microporous and biological characteristics, has attracted great attention in many application fields. In this paper, the potential of bamboo charcoal to act as a solid-phase extraction (SPE) adsorbent for the enrichment of the environmental pollutant perfluorooctanoic acid, which is one of the newest types of persistent organic pollutants in the environment, has been investigated. Important factors that may influence the enrichment efficiency—such as the eluent and its volume, the flow rate of the sample, the pH of the sample and the sample volume—were investigated and optimized in detail. Under the optimum conditions, the limit of detection for PFOA was 0.2 ng L⁻¹. The experimental results indicated that this approach gives good linearity (R ² = 0.9995) over the range 1–1000 ng L⁻¹ and good reproducibility, with a relative standard deviation of 4.0% (n = 5). The proposed method has been applied to the analysis of real water samples, and satisfactory results were obtained. The average spiked recoveries were in the range 79.5∼118.3 %. All of the results indicate that the proposed method could be used for the determination of PFOA at ultratrace levels in water samples.     

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.