Bamboo charcoal as a novel solid-phase microextraction coating material for enrichment and determination of eleven phthalate esters in environmental water samples

This study demonstrates the potential of bamboo charcoal as a novel and inexpensive solid-phase microextraction (SPME) coating material for enrichment and determination of organic pollutants in water samples. Bamboo charcoal was prepared and used as a SPME coating material. Eleven phthalate esters (PAEs) were used as model analytes, and gas chromatography–mass spectrometry was used for separation and detection. Important extraction conditions (ionic strength, stirring rate, and extraction time) and desorption conditions (desorption temperature and time) were systematically investigated and optimized. Linearity of 0.1–100 μg?L^?1 and correlation coefficients of 0.9992–0.9998 were obtained under optimum conditions. Inter-day and intra-day repeatability were 2.15–9.93 % and 1.89–9.85 %, respectively, and fiber-to-fiber reproducibility was 5.42–9.66 %. On the basis of a chromatographic signal-to-baseline noise ratio of three, the limits of detection reached 0.004–0.023 μg?L^?1. Satisfactory results were achieved when the bamboo coating was used for determination of 11 PAEs in real water samples. The experimental results indicate that bamboo charcoal has significant potential as a SPME coating material for rapid enrichment and sensitive determination of organic pollutants in environmental samples.     

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.     

Highly sensitive determination of tetrabromobisphenol A and bisphenol A in environmental water samples by solid‐phase extraction and liquid chromatography‐tandem mass spectrometry

Using bamboo‐activated charcoal as SPE adsorbent, a novel SPE method was developed for the sensitive determination of tetrabromobisphenol A and bisphenol A in environmental water samples by rapid‐resolution LC‐ESI‐MS/MS. Important parameters influencing extraction efficiency, including type of eluent, eluent volume, sample pH, volume and flow rate, were investigated and optimized. Under the optimal extraction conditions (eluent: 8 mL methanol, pH: 7; flow rate: 4 mL/min; sample volume: 100 mL), low LODs (0.01–0.02 ng/mL), good repeatability (6.2–8.3%) and wide linearity range (0.10–10 ng/mL) were obtained. Satisfied results were achieved when the proposed method was applied to determine the two target compounds in real‐world environmental water samples with spiked recoveries over the range of 80.5–119.8%. All these facts indicate that trace determination of tetrabromobisphenol A and bisphenol A in real‐world environmental water samples can be realized by bamboo‐activated charcoal SPE‐rapid resolution‐LC‐ESI‐MS/MS.     

Simultaneous Analysis of Organophosphorus Pesticides in Water by Magnetic Solid-Phase Extraction Coupled with GC–MS

Magnetic solid-phase extraction (MSPE) coupled with gas chromatography–mass spectrometry was applied for the analysis of organophosphorus pesticides (OPPs) in water samples. We chose C18-functionalized Fe₃O₄@mSiO₂ microspheres as the magnetic sorbents to extract and enrich OPPs from water samples with the advantages of good solubility in water, large surface area and fast separation ability. In this study, six kinds of OPPs were analyzed and various parameters of MSPE procedure, including eluting solvent, the amount of magnetic absorbents and extraction time were optimized. Validation experiments showed that the optimized method had good linearity with correlation coefficients r ² > 0.98 and satisfactory precision with the relative standard deviation ≤10.7 %. The limits of detection were 1.8–5.0 μg L^?1 and the limits of quantification ranged from 6.1 to 16.7 μg L^?1. We concluded that the proposed method was successfully applied to analyze OPPs in real water samples and the results indicated that it had the advantages of simplicity, convenience and efficiency.     

Electrochemical determination of nitrite in water samples using a glassy carbon electrode modified with didodecyldimethylammonium bromide

Multiwalled carbon nanotubes were used as solid phase extraction (SPE) adsorbent for the determination of four chloroacetanilide herbicides (alachlor, acetochlor, metolachlor and butachlor) in water. The primary factors that influence the efficiency of the SPE performance, such as the amount of the adsorbent, the eluent solvent, the pH and the sample volume, were investigated and optimized. Under optimized conditions, the recoveries of the four herbicides at three spike levels were in the range 76.7–104.4%, and the RSDs ranged from 2.5–12.7%. Good linearity was obtained for the pesticides in the concentration range 0.0025–2.5 mg L^?1, and the detection limits were 0.01–0.03 μg L^?1 at signal-to-noise ratios of 3:1. The method was successfully applied to the determination of these analytes in tap water and river water.     

Application of bamboo charcoal as solid-phase extraction adsorbent for the determination of atrazine and simazine in environmental water samples by high-performance liquid chromatography-ultraviolet detector

In this article, a new method for the determination of triazine herbicides atrazine and simazine in environment aqueous samples was developed. It was based on solid-phase extraction (SPE) using bamboo charcoal as adsorbent and high-performance liquid chromatography-ultraviolet detector (HPLC-UV) for the enrichment and determination of atrazine and simazine at trace level. Related important factors influencing the extraction efficiency, such as the kind of eluent and its volume, flow rate of the sample, pH of the sample, and volume of the sample, were investigated and optimized in detail. Under the optimal conditions, the experimental results showed that excellent linearity was obtained over the range of 0.5–30 μg L⁻¹ with correlation coefficients 0.9991 and 0.9982, for atrazine and simazine, respectively; and the relative standard deviations of two analytes were 8.3, 8.7%, respectively. The proposed method was successfully applied to the analysis of tap water and well water samples. And satisfactory spiked recoveries were obtained in the range of 75.2–107.1%. The above results indicated that the developed method was an excellent alternative for the routine analysis in environmental field.     

Simultaneous determination of seven metal ions in water samples by solid-phase extraction on polyacrylonitrile activated carbon fibres

A new solid-phase extraction method utilising polyacrylonitrile activated carbon fibres (PAN-ACFs) as adsorbent was developed for the preconcentration of trace metal ions prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The PAN-ACFs oxidised with nitric acid were characterised by FT-IR, XRD, SEM and BET analysis. Then the resulting PAN-ACFs were used as solid-phase adsorbent for simultaneously determination of trace Al(III), Be(II), Bi(III), Cr(III), Cu(II), Fe(III) and Pb(II) ions in aqueous solutions. The influences of the analytical parameters on the recoveries of the studied ions were investigated. The optimum experimental conditions of the proposed method were pH: 6.0; eluent concentration and volume: 3.0 mL of 1.5 mol L^?1 nitric acid; flow rates of sample and eluent solution: 1.5 mL min^?1. The preconcentration factors were found to be 67 for Al(III), Bi(III); 83 for Cr(III), Cu(II), Fe(III) and 50 for Be(II), Pb(II). The precision of this method was in range of 1.5%~3.5% and the detection limit of this metal ions was between 0.06~1.50 μg L^?1. The developed method was validated by the analysis of a certified reference sample and successfully applied to the determination of trace metal ions in water samples with satisfactory results.     

Development of graphene-carbon nanotube-coated magnetic nanocomposite as an efficient sorbent for HPLC determination of organophosphorus pesticides in environmental water samples

A magnetic solid-phase extraction (MSPE) method coupled to high performance liquid chromatography with UV (HPLC-UV) was proposed for the determination of organophosphorus pesticides (OPPs) at trace levels in environmental water samples. The ternary nanocomposite of graphene-carbon nanotube-Fe₃O₄ (G-CNT-Fe₃O₄) has been synthesised via a simple solvothermal process and the resultant material was characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Significant factors that affect the extraction efficiency, such as amount of magnetic nanocomposite, extraction time, ionic strength, solution pH and desorption conditions were carefully investigated. The results demonstrated that the proposed method had a wide dynamic linear range (0.005–200 ng mL^?1), good linearity (R² = 0.9955–0.9996) and low detection limits (1.4–11 pg mL^?1). High enrichment factors were achieved ranging from 930 to 1510. The results show that the developed method is suitable for trace level monitoring of OPPs in environmental water samples.     

Determination of trace organophosphorus pesticides in water samples with TiO2 nanotubes cartridge prior to GC‐flame photometric detection

This article described a new method for the sensitive determination of organophosphorus pesticides in water samples using SPE in combination with GC‐flame photometric detection. In the procedure of method development, TiO₂ nanotubes were used as SPE adsorbents for the enrichment of organophosphorus pesticides from water samples. Several factors, such as eluent and its volume, sample pH, sample volume, sample flow rate, and concentration of humic acid, were optimized. Under the optimal conditions, the proposed method had good linear ranges as 0.1–40 μg/L for each of them, LOD of 0.11, 0.014, and 0.0025 μg/L, and LOQs of 0.37, 0.047, and 0.0083 μg/L for chlorpyrifos, phorate, and methyl parathion, respectively. The proposed method was validated with real environmental water samples and the spiked recoveries were over the range of 86.5–115.1%. All these results indicated that TiO₂ nanotubes, as a new SPE adsorbent, would be used widespread for the preconcentraiton and determination of environmental pollutants in the future.     

Simultaneous Analysis of Carbamate and Organophosphorus Pesticides in Water by Single-Drop Microextraction Coupled with GC–MS

Single-drop microextraction (SDME) has been coupled with gas chromatography–mass spectrometry to enable rapid and simple simultaneous analysis of carbamate and organophosphorus pesticides (OPP). The significant conditions affecting SDME performance (microextraction solvent, extraction time, solvent volume, sample pH, stirring speed, and ionic strength) were studied and optimized. Extraction was achieved by suspending a 1.5-μL drop of toluene from the tip of a microsyringe directly immersed in 5-mL aqueous donor solution at pH 5 stirred at 800 rpm. The dynamic linear range and detection limits of the method were evaluated by analysis of water samples spiked with carbamate pesticides and OPP. Under selected ion-storage mode, very low detection limits (0.02–0.50 ng mL^?1) and good linearity (0.5–200 ng mL^?1) were achieved. When SDME was applied to analysis of pesticides in natural water samples good recoveries (89.4–102.1%) were obtained. Inter-day and intra-day RSD of most results were below 5.4 and 6.1%, respectively. The method proved to be a rapid and simple tool for extraction and analysis of these pesticides in water samples.     

Application of modified multiwalled carbon nanotubes for palladium preconcentration and determination in water and soil samples by flame atomic absorption spectrometry

A new solid-phase extraction method for determination of palladium by atomic absorption spectrometry is described. Multiwalled carbon nanotube (MWCNT) modified with 1-butyl 3-methyl imidazolium hexafluorophosphate (MWCNT-[BMIM]PF₆) and supported on sawdust was used as an adsorbent for preconcentration of palladium. Palladium ions are retained on (MWCNT-[BMIM]PF₆) adsorbent as [PdI₄]^2? and eluted from the column with a thiosulfate–ammonia mixture. The optimum conditions for the adsorption were evaluated by changing various parameters such as pH, sample volume, concentration and volume of eluent, iodide concentration and interfering ions to achieve highest sensitivity and selectivity. The calibration graph was linear in the range of 2–120 ng mL^?1 of palladium in the initial solution and the limit of detection based on 3S_b was 0.41 ng mL^?1. The method was applied to the determination of palladium in water, wastewater and soil samples.     

Determination of Six Organophosphorus Pesticides in Water by Single-Drop Microextraction Coupled with GC-NPD

A single-drop microextraction (SDME) procedure with a modified microsyringe was developed for the analysis of six organophosphorus pesticides (OPPs) in water. Microsyringe was modified by attaching a 2-mm cone onto the needle tip end. The conditions affecting SDME performance including microextraction solvent, stirring speed, extraction time, ionic strength and sample pH were optimized. Under the optimized conditions, the linear ranges of the SDME with ethion as internal standard were 0.05–50 μg L^?1 (except for dimethoate 5–5,000 μg L^?1) and limits of detection (LOD) were 0.012–0.020 μg L^?1 (except for dimethoate 0.45 μg L^?1). Recoveries of six pesticides were in the range of 70.6–107.5 % with relative standard deviation lower than 6.0 %. The modified method is simple, rapid and sensitive, and acceptable in the analysis of OPPs pesticides in water samples.     

Determination of Organophosphorus Pesticides in Leeks (Allium porrum L.) by GC-FPD

A method was validated for the analysis of organophosphorus pesticides in leeks. The leek sample was cut into about 2 cm lengths and heated in a microwave oven for 50 s to inactivate enzymes. The sample was extracted with 50 mL acetonitrile using an Ultra-turrax T18 blender and cleaned up by solid phase extraction. The target analytes were determined by GC with a flame photometric detector. Average recoveries were 73–118% and limits of detection ranged from 1.1 to 10.0 μg kg^?1. The uncertainty of the analysis for each pesticide was evaluated as below 16%. The method was applied to determine organophosphorus pesticides in real samples. The GC–MS was used as confirmatory tool for positive samples.     

Facile synthesis of magnetic MWCNT functionalised 8-hydroxyquinoline: characterisation and application for selective enrichment of cadmium ions in food samples

A simple and efficient approach for preparing modified magnetic multi-walled carbon nanotubes (MMWCNT) with 8-hydroxyquinoline was developed. This short-cut method has reduced the contact time of modification from 2 days to 10 hours. The properties of MMWCNT modified 8-hydroxyquinoline were characterised by scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and Fourier transform infrared spectrophotometer (FT-IR). This adsorbent was found to be a new, selective, low-cost and high capacitance for enrichment of cadmium in solid-phase extraction (SPE). In addition, based on the easily separated modified MMWCNT from the aqueous solutions with the help of an external magnet, no filtration or centrifugation was needed. The variables of interest in the SPE, such as pH, ionic strength, extraction time, desorption time, type and volume and concentration of eluent, were optimised. The calibration graph was linear over the range of 0.42–127 μg l^?1. The limit of detection was 0.12 μg l^?1 and the relative standard deviation of 2.25% at 30 ng ml^?1 Cd(II) ions was obtained (n = 8). The preconcentration factor and adsorption capacity of the sorbent were 160 and 60.2 mg g^?1 respectively. Finally, practical applicability of the developed adsorbent was confirmed by preconcentration of Cd(II) ions from water, vegetable and food samples.     

A zinc(II) benzenetricarboxylate metal organic framework with unusual adsorption properties,and its application to the preconcentration of pesticides

The authors describe a zinc(II) benzenetricarboxylate (Zn-BTC) based metal-organic framework (MOF) with chrysanthemum-like structure, and its application to the adsorption of pesticides from real water samples. The Zn-BTC MOF was characterized by XRD, TGA, SEM, nitrogen adsorption-desorption analysis and FT-IR spectroscopy. The MOF was used in dispersive solid-phase extraction of six aromatic pesticides from various wastewater samples prior to their quantification by HPLC. Extraction times, extraction temperature, amount of adsorbent, and oscillation rate were optimized. Under the optimal conditions, the method has relative standard deviations (RSDs) of 6.1–10.1%, and good linearity (correlation coefficients higher than 0.9974). The LODs and LOQs for seven pesticides are found to be 0.20–1.60 μg·L^?1 and 0.66–5.28 μg·L^?1, respectively. The RSDs of within batch extraction are 1.6–9.5% and 3.9–12%.

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Graphical abstract Schematic of a zinc-benzenetricarboxylate (Zn-BTC) based metal-organic framework (MOF) for use as an adsorbent of dispersive solid phase extraction (DSPE) of pesticides prior to their determination by HPLC.

     

Multiwalled Carbon Nanotubes as SPE Adsorbents for Simultaneous Determination of Seven Sulfonylurea Herbicides in Environmental Water by LC–MS–MS

An effective and rapid method was developed for simultaneous determination of seven sulfonylurea herbicides in environmental water using multiwalled carbon nanotubes as solid-phase extraction sorbent coupled with liquid chromatography–tandem mass spectrometry. Important parameters influencing the extraction efficiency such as pH of the sample solution, flow rate of sample loading, the eluent and its volume were optimized. Under optimum conditions, good linearity was obtained for all herbicides (r ² > 0.99) over the range of 0.05–5,000 ng L^?1, and precisions (RSD) for nine replicate measurements of a standard mixture of 200 ng L^?1 were 1.9–7.4%. The limits of detection and quantification were 0.01–0.20 and 0.05–1.00 ng L^?1, respectively. The proposed method was successfully applied to the analysis of tap water, spring water, ground water and well water, and mean recoveries for seven analytes at three spiked concentration levels were from 81.5 to 110.5% with RSDs between 0.3 and 7.0%. The results showed that the established method has wide application to analyze sulfonylurea herbicides at trace level in water.     

Investigation of feasibility of bamboo charcoal as solid-phase extraction adsorbent for the enrichment and determination of four phthalate esters in environmental water samples

This paper demonstrates, for the first time, that adsorptive potential of bamboo charcoal for solid-phase extraction of phthalate esters was investigated. The four phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl benzyl phthalate (BBP) and di-n-butyl phthalate (DBP), are quantitatively adsorbed on a bamboo charcoal packed cartridge, then the analytes retained on the cartridge are quantitatively desorbed with optimum amounts of acetone. Finally, the analytes in the eluant acetone are determined by high-performance liquid chromatography-ultraviolet detectior. Important parameters influencing the extraction efficiency, such as eluant and its volume, flow rate of sample, sample volume, pH, the amount of adsorbent and ionic strength were investigated and optimized in detail. Under the optimum conditions, the limits of detection were 0.35-0.43 microg/L for four phthalate esters. The proposed method has been applied to the analysis of rainwater and tap water samples. And satisfactory spiked recoveries were obtained in the range of 75.0-114.2%. All the results indicated that the bamboo charcoal has great potential as a novel adsorbent material for the enrichment and determination of phthalate esters in real environmental water samples.     

Magnetic solid-phase extraction to preconcentrate trace amounts of gold (III) using nickel ferrite magnetic nanoparticles

In this research, nickel ferrite (NiFe₂O₄) magnetic nanoparticles were synthesised by a simple method and applied as sorbent for magnetic solid-phase extraction of trace amounts of Au(III) from water samples. Detection in this technique was performed by flame atomic absorption spectrometry. The effects of sample pH, amount of sorbent, extraction time, desorption solvent and its volume on the extraction process were optimised. The effects of interfering ions on the recovery of the analyte were also evaluated in model solutions. The best results were obtained at pH 6.5 with 5 mL of eluent solution (0.1 mol L^?1 sodium thiosulphate) and an extraction time of 30 min. Under optimal conditions, the sorption capacity was 34.6 mg g^?1. Also, enhancement factor (for 100 mL of sample solution) was found to be 19.3. The calibration graph was linear in the range of 4.4–800.0 µg L^?1 gold concentration and the limit of detection was 1.32 µg L^?1. The relative standard deviation of the method (for n = 8) was 1.57%. The method was successfully applied to the extraction of Au(III) from water samples.     

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.     

Polythionine-decorated magnetic nanoparticles as a robust and highly effective sorbent for mercury determination in environmental water samples

Extraction, pre-concentration and determination of trace amounts of mercury ions from water samples were investigated by magnetic solid phase extraction (MSPE) method using Fe₃O₄ nanoparticles decorated with polythionine as an adsorbent. A simple chemical synthesis by catalytic reaction of thionine in the presence of FeCl₃ and hydrogen peroxide was used for preparation of the magnetic sorbent. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometer analysis and Fourier transform infrared spectroscopy were used to characterise the adsorbent. Mercury ions were determined by cold vapour atomic absorption spectrometry. The parameters for MSPE procedure, such as pH of the extraction solution, adsorption time, weight adsorbent, elution conditions (type, concentration and volume of the eluent), volume of the sample solution and effects of coexisting ions were investigated. The obtained optimal conditions were: sample pH of 4; sorbent amount of 4 mg; sorption time of 20 min; elution solvent of HNO₃ (0.3 mol L^?1)/thiourea (2% w/v) with volume of 2 mL, and breakthrough volume of 400 mL. A good linearity in the concentration range of 0.025–40 µg L^?1 (R² > 0.999) with the pre-concentration factor of 198 was obtained. The limits of detection and quantification were achieved as 0.008 and 0.025 µg L^?1, respectively. Furthermore, sea and river water samples were analysed and good recoveries (97.1–99.6%) were obtained.