Hydride generation atomic absorption spectrometric determination of bismuth after separation and preconcentration with modified alumina

A simple and sensitive method has been developed for the trace determination of bismuth in aqueous samples by a combination of solid‐phase extraction and hydride generation atomic absorption spectrometry. The method is based on the use of a column packed with 2‐mercaptobenzothiazole immobilized on sodium dodecyl sulfate coated alumina. Different parameters influencing the separation and preconcentration of bismuth such as pH, sample volume, type, and concentration of eluent, and the flow rate of sample and eluent were studied. A sample volume of 500.0 mL resulted in a preconcentration factor of 100. The precision (relative standard deviation, N = 10) at the 300 ng/L level and the limit of detection (3s) were found to be 2.3% and 12 ng/L, respectively. The developed method was successfully applied to the determination of bismuth in natural water samples and two certified reference materials.     

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.     

Application of a dispersive micro‐solid‐phase extraction method for pre‐concentration and ultra‐trace determination of cadmium ions in water and biological samples

A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic‐assisted dispersive micro‐solid‐phase extraction (UA‐D‐μSPE) was developed. Silica‐coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X‐ray diffraction. Following UA‐D‐μSPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box–Behnken design was used for optimization of important sorption and desorption parameters in UA‐D‐μSPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3 min; sorption amount, 35 mg; type and concentration of eluent, HCl and 1.1 mol l^?1; volume of eluent, 360 μl; sonication time for desorption, 110 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA‐D‐μSPE were found to be 0.8 ng l^?1 and <6%, respectively.     

Flame atomic absorption spectrometry for the determination of trace amount of rhodium after separation and preconcentration onto modified multiwalled carbon nanotubes as a new solid sorbent

The present article reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace rhodium ion in aqueous solution. Rhodium ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) in the pH range of 3.2-4.7 and then the formed Rh-PAN complex was adsorbed on the oxidized MWCNTs. The adsorbed complex was eluted from MWCNTs sorbent with 5.0 mL of N,N-dimethylformamide (DMF). The rhodium in eluted solution was determined by flame atomic absorption spectrometry (FAAS). Linear range for the determination of rhodium was maintained between 0.16 ng mL⁻¹ and 25.0 μg mL⁻¹ in initial solution. Relative standard deviation for the 10 replicated determination of 4.0 μg mL⁻¹ of rhodium was ±0.97%. Detection limit was 0.010 ng mL⁻¹ in initial solution (3S_bl, n = 10) and preconcentration factor was 120. Sensitivity for 1% absorbance of rhodium (III) was 0.112 μg mL⁻¹. The sorption capacity of oxidized MWCNTs for Rh (III) was 6.6 mg g⁻¹. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions were studied for the preconcentration of Rh³⁺. The proposed method was successfully applied to the extraction and determination of rhodium in different samples.     

Separation,preconcentration and speciation of chromium by solid phase extraction on immobilised ferron

A sensitive and simple method for determination of chromium species after separation and preconcentration by solid phase extraction (SPE) has been developed. For the determination of the total concentration of chromium in solution, Cr(VI) was efficiently reduced to Cr(III) by addition of hydroxylamine and Cr(III) was preconcentrated on a column of immobilised ferron on alumina. The adsorbed analyte was then eluted with 5?mL of hydrochloric acid and was determined by flame atomic absorption spectrometery. The speciation of chromium was affected by first passing the solution through an acidic alumina column which retained Cr(VI) and then Cr(III) was preconcentrated by immobilised ferron column and determined by FAAS. The concentration of Cr(VI) was determined from the difference of concentration of total chromium and Cr(III). The effect of pH, concentration of eluent, flow rate of sample and eluent solution, and foreign ions on the sorption of chromium (III) by immobilised ferron column was investigated. Under the optimised conditions the calibration curve was linear over the range of 2–400?µg?L^?1 for 1000?mL preconcentration volume. The detection limit was 0.32?µg?L^?1, the preconcentration factor was 400, and the relative standard deviation (%RSD) was 1.9% (at 10?µg?L^?1; n?=?7). The method was successfully applied to the determination of chromium species in water samples and total chromium in standard alloys.     

固相萃取-高效液相色谱法同时检测水样中戊唑醇、乙霉威、晴菌唑、精甲霜灵和扑草净5种农药残留

利用石墨烯固相萃取柱萃取、高效液相色谱分离紫外检测,建立了戊唑醇、乙霉威、晴菌唑、精甲霜灵和扑草净5种农药同时检测的方法。确定的优化条件为:洗脱剂为5mL二氯甲烷、样品溶液的pH=7.0,样品体积为200mL。在此条件下,扑草净、戊唑醇、乙霉威、晴菌唑和精甲霜灵在0.05～100μg/L浓度范围内与峰面积呈良好的线性关系,相关系数为0.895～0.992;信噪比为3时,5种农药的检出限为1.2～5.2ng/L;方法的精密度为1.4%～4.6%。将本方法用于环境水样标准加入分析,相对回收率为80.5%～107.6%;相对标准偏差均小于5%。     

Electrospun polyethylene terephthalate/graphene oxide nanofibrous membrane followed by HPLC for the separation and determination of tamoxifen in human blood plasma

An electrospun polyethylene terephthalate/graphene oxide nanofibrous mat was fabricated and used as an effective and novel membrane for the solid‐phase extraction of tamoxifen in human blood plasma samples before detection by high‐performance liquid chromatography. The membrane was characterized by some identification techniques, such as FTIR spectroscopy, X‐ray diffraction, and scanning electron microscopy. The effective variables of the extraction procedure including desorption condition (type and volume of the eluent), adsorbent dose, pH of sample solution, salt concentration, and sample loading time were investigated and their optimum values were obtained using one factor at a time methodology. Under the optimized conditions, the results showed wide linear concentration range of 5–2000 ng/mL with a determination coefficient of 0.992. The limits of detection and limits of quantification were 1.3 and 5.0 ng/mL, respectively. The intra‐day and inter‐day precisions were 3.4 and 4.6%, respectively. The method was successfully applied to determination of tamoxifen in the blood plasma samples and satisfactory relative recoveries (92.6–98.3 %) were achieved.     

Separation and Determination of Diol Pollutants Come from Demulsifier in the Produced Water of Oil Fields

This paper introduced a novel test method for determination of the main demulsifier‐based pollutants in the produced water of oil wells, before draining to seawater. The type, concentration and distribution of diols depend on the demulsifier of interest; however, the main chemical species are the same. The novelty of this work is selective extraction and preconcentration of low chain diols in the produced water of oil fields. In this extraction method, dispersive solvent (1.2 mL, acetonitrile) containing extraction solvent (10.0 μL, carbon tetrachloride) was rapidly injected into the water sample containing analytes, and a cloudy solution was formed. After centrifugation (2 min at 3,000 rpm), these droplets were sedimented in the bottom of the conical test tube. Then 2.0 mL of sedimented phase containing preconcentrated analytes was injected into the gas chromatograph with flame ionization detector. The parameters affecting the extraction efficiency were evaluated and optimized. Factors such as the kind and volume of both extraction and disperser solvents, extraction and centrifugation times, pH and temperature, and salt effect were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 39.0 to 44.4 and 78.9 to 92.2%, respectively, within very short extraction time. The linearity (and limit of detection) of the method ranged 4.0‐100.0 (2.0) ng/mL for 1,2‐ethandiol, 6.0‐80.0 (4.0) ng/mL for 1,3‐propandiol, 2.0‐90.0 (1.0) ng/mL ng/mL for 1,4‐butanediol, 5.0‐120.0 (2.0) ng/mL for 1,5‐pentandiol. The relative standard deviations (RSD) for the concentration of diols, 5.0 ng/mL in water by using the internal standard were in the range of 1.5–4.5% (n = 5) and without the internal standard was in the range of 2.6–9.0% (n = 5). It is concluded that this method is successful for determination of diols in produced water samples.     

Preparation of metal‐organic framework UiO‐66‐incorporated polymer monolith for the extraction of trace levels of fungicides in environmental water and soil samples

A zirconium terephthalate metal‐organic framework‐incorporated poly(N‐vinylcarbazole‐co‐divinylbenzene) monolith was fabricated in a capillary by a thermal polymerization method. The optimized monolith had a homogeneous structure, good permeability, and stability. The monolith could be used for the effective enrichment of fungicides through π‐π interactions, electrostatic forces, and hydrogen bonds. The potential factors that affect the extraction efficiency, including ionic strength, solution pH, sample volume, and eluent volume, were investigated in detail. The monolith‐based in‐tube solid‐phase microextraction coupled with ultra‐high‐performance liquid chromatography and high‐resolution Orbitrap mass spectrometry was performed for the analysis of five fungicides (pyrimethanil, tebuconazole, hexaconazole, diniconazole, and flutriafol) in environmental samples. Under the optimized conditions, the linear ranges were 0.005–5 ng/mL for pyrimethanil, 0.01–5 ng/mL for flutriafol, and 0.05–5 ng/mL for other fungicides, respectively, with coefficients of determination ≥0.9911. The limits of detection were 1.34–14.8 ng/L. The columns showed good repeatability (relative standard deviations ≤9.3%, n = 5) and desirable column‐to‐column reproducibility (relative standard deviations 5.3–9.4%, n = 5). The proposed method was successfully applied for the simultaneous detection of five fungicides in water and soil samples, with recoveries of 90.4–97.5 and 84.0–95.3%, respectively.     

Molecularly imprinted polymeric stir bar: Preparation and application for the determination of naftopidil in plasma and urine samples

In this study, molecularly imprinting technology and stir bar absorption technology were combined to develop a microextraction approach based on a molecularly imprinted polymeric stir bar. The molecularly imprinted polymer stir bar has a high performance, is specific, economical, and simple to prepare. The obtained naftopidil‐imprinted polymer‐coated bars could simultaneously agitate and adsorb naftopidil in the sample solution. The ratio of template/monomer/cross‐linker and conditions of template removal were optimized to prepare a stir bar with highly efficient adsorption. Fourier transform infrared spectroscopy, scanning electron microscopy, selectivity, and extraction capacity experiments showed that the molecularly imprinted polymer stir bar was prepared successfully. To utilize the molecularly imprinted polymer stir bar for the determination of naftopidil in complex body fluid matrices, the extraction time, stirring speed, eluent, and elution time were optimized. The limits of detection of naftopidil in plasma and urine sample were 7.5 and 4.0 ng/mL, respectively, and the recoveries were in the range of 90–112%. The within‐run precision and between‐run precision were acceptable (relative standard deviation <7%). These data demonstrated that the molecularly imprinted polymeric stir bar based microextraction with high‐performance liquid chromatography was a convenient, rapid, efficient, and specific method for the precise determination of trace naftopidil in clinical analysis.     

Application of a thiourea‐containing task‐specific ionic liquid for the solid‐phase extraction cleanup of lead ions from red lipstick,pine leaves,and water samples

Here, task‐specific ionic liquid solid‐phase extraction is proposed for the first time. In this approach, a thiourea‐functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid‐phase extraction column are used for the selective extraction and preconcentration of ultra‐trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5–40.0 ng/mL with the detection limit of 0.13 ng/mL (3s_b/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents.     

Simultaneous determination of palladium, platinum, rhodium and gold by on-line solid phase extraction and high performance liquid chromatography with 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine as pre-column derivatization regents

In this paper, 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine (HNATR) was synthesized. A new method for the simultaneous determination of palladium, platinum, rhodium and gold ions as metal-HNATR chelates was developed using a rapid analysis column high performance liquid chromatography equipped with on-line solid phase extraction technique. The samples (Water, human urine, geological samples and soil) were digested by microwave acid-digestion. The palladium, platinum, rhodium and gold ions in the digested samples were pre-column derivatized with HNATR to form colored chelates. The Pd-HNATR, Pt-HNATR, Rh-HNATR and Au-HNATR chelates can be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column [Zorbax Stable Bound, 10 mm x 4.6 mm, 1.8 microm] with a buffer solution of 0.05 mol L(-1) phosphoric acid as mobile phase. After the enrichment had finished, by switching the six ports switching valve, the retained chelates were back-flushed by mobile phase and travelling towards the analytical column. These chelates separation on the analytical column [Zorbax Stable Bound, 10 mm x 4.6 mm, 1.8 microm] was satisfactory with 72% acetonitrile (containing 0.05 mol L(-1) of phosphoric acid and 0.1% of Triton X-100) as mobile phase. The palladium, platinum, rhodium and gold chelates were separated completely within 2.5 min. Compared to the routine chromatographic method, more then 80% of separation time was shortened. By on-line solid phase extraction system, a large volume of sample (10 mL) can be injected, and the sensitivity of the method was greatly improved. The detection limits (S/N=3, the sample injection volume is 10 mL) of palladium, platinum, rhodium and gold in the original samples reaches 1.4, 1.8, 2.0 and 1.2 ng L(-1), respectively. The relative standard deviations for five replicate samples were 2.4-3.6%. The standard recoveries were 88-95%. This method was applied to the determination of palladium, platinum, rhodium and gold in human urine, water and geological samples with good results.     

Porous‐membrane‐protected polyaniline‐coated SBA‐15 nanocomposite micro‐solid‐phase extraction followed by high‐performance liquid chromatography for the determination of parabens in cosmetic products and wastewater

A SBA‐15/polyaniline para‐toluenesulfonic acid nanocomposite supported micro‐solid‐phase extraction procedure has been developed for the extraction of parabens (methylparaben, ethylparaben, and propylparaben) from wastewater and cosmetic products. The variables of interest in the extraction process were pH of sample, sample and eluent volumes, sorbent amount, salting‐out effect, extraction and desorption time, and stirring rate. A Plackett–Burman design was performed for the screening of variables in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by using a central composite design. The optimum experimental conditions found at 50 mL sample solution, extraction and desorption times of 40 and 20 min, respectively, 500 μL of 3% v/v acetic acid in methanol as eluent, 0.01 M salt addition, and 10 mg of the sorbent. Under the optimum conditions, the developed method provided detection limits in the range of 0.08–0.4 ng/mL with good repeatability (RSD% < 7) and linearity (r² = 0.997–0.999) for the three parabens. Finally, this fast and efficient method was employed for the determination of target analytes in cosmetic products and wastewater, and satisfactory results were obtained.     

Solid phase extraction of trace amounts of uranium(VI) from water samples using 8-hydroxyquinoline immobilized on surfactant-coated alumina

A simple and reliable method has been developed for the determination of uranium(VI). The method is based on the separation and preconcentration of uranium(VI) using a column packed with 8-hydroxyquinoline immobilized on surfactant coated alumina prior to its spectrophotometric determination with arsenazo III. The effect of pH, sample flow rate and volume, elution conditions, and foreign ions on the sorption of uranium(VI) has been investigated. A preconcentration factor of 200 was achieved by passing 1000 mL of sample through the column. The relative standard deviation for 10 replicate analyses at the 100 ng/mL level of uranium(VI) was 2.1% and the detection limit was 0.12 ng/mL. The method was success-fully applied to the determination of uranium in natural water samples. The accuracy was assessed through recovery experiments and the analysis of a certified reference material.     

Solid phase extraction of trace amounts of uranium(VI) from water samples using 8-hydroxyquinoline immobilized on surfactant-coated alumina

A simple and reliable method has been developed for the determination of uranium(VI). The method is based on the separation and preconcentration of uranium(VI) using a column packed with 8-hydroxyquinoline immobilized on surfactant coated alumina prior to its spectrophotometry determination with Arsenazo III. The effect of pH, sample flow rate and volume, elution conditions, and foreign ions on the sorption of uranium(VI) has been investigated. A preconcentration factor of 200 was achieved by passing 1000 mL of sample through the column. The relative standard deviation for 10 replicate analyses at the 100 ng/mL level of uranium(VI) was 2.1% and the detection limit was 0.12 ng/mL. The method was successfully applied to the determination of uranium in natural water samples. The accuracy was assessed through recovery experiments and the analysis of a certified reference material.     

Chemical modification of alumina surface by immobilization of 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide for extractive concentration of silver ions

A column, solid phase extraction (SPE), preconcentration method was developed for determination of silver by using alumina coated with 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide and determination by flame atomic absorption spectrometry. The separation/preconcentration conditions for the quantitative recovery were investigated. At pH 2, the maximum sorption capacity of Ag⁺ was 7.5?mg?g^?1. The linearity was maintained in the concentration range of 0.02–11.0?µg?mL^?1 in the final solution or 0.14–1.10?×?10^4?ng?mL^?1 in the original solution for silver. The preconcentration factor of 140 and relative standard deviation of ±1.4% was obtained, under optimum conditions. The limit of detection (LOD) was calculated as 0.112?ng?mL^?1, based on 3σ_bl/m (n?=?8) in the original solutions. The proposed method was successfully applied to the determination trace amounts of silver in the environmental samples such as tea, rice and wheat flour, mint, and real water samples.     

Separation and preconcentration of trace amounts of gold(III) ions using modified multiwalled carbon nanotube sorbent prior to flame atomic absorption spectrometry determination

Multiwalled carbon nanotubes are attractive as sorbents for SPE because they can be used for enrichment of organic compounds and metal ions at trace levels. In this study, multiwalled carbon nanotubes were oxidized with concentrated HNO3, and then the oxidized multiwalled carbon nanotubes were modified with 5-(4'-dimethylamino-benzyliden)-rhodanine. The modified multiwalled carbon nanotubes were used as a solid sorbent for separation and preconcentration of trace amounts of Au(III) ions. The sorption of Au(III) ions was quantitative in the pH range of 2.0-5.0, whereas quantitative desorption occurred instantaneously with 5.0 mL 2.0 M Na2S2O3. The eluted solution was aspirated directly into the flame for atomic absorption spectrometry. The proposed method resulted in an enrichment factor of 94. The RSD of the method was +/- 1.11% (n=10, 2.0 microg/mL) and the LOD was 0.15 ng/mL. The calibration curve for Au(III) was linear between 0.53 ng/mL and 36.0 microg/mL in the initial solution, with an R2 value of 0.9999. The sorbent capacity of the modified multiwalled carbon nanotubes was 7.3 mg Au(III)/g sorbent. The influences of the experimental parameters, including sample pH, sample flow rate, eluent volume and flow rate, sample volume, and interference of some ions on the recoveries of the Au ions, were investigated. The proposed method was applied for preconcentration and determination of Au in different samples.     

Determination of Copper by Flame Atomic Absorption Spectrometry after Preconcentration with Activated Carbon Impregnated with a New Schiff Base

A simple and reliable method for the extraction and determination of trace amounts of copper（Ⅱ） ions using activated carbon （AC） impregnated by a new Schiff base 5-[（4-heptyloxyphenyl）azo]-N-（4-propyloxyphenyl）-salicylaldimine （HPPS） and atomic absorption spectrometry is presented. Recovery efficiency and the influence of pH value, volume of sample solution, effect of different eluents, and interfering ions were evaluated. The limit of detection （3σ） was 2.62 ng.mL^-1 and the relative standard deviation （n=10） was 1.5%. Under optimum conditions, the copper ions were concentrated 25 fold using 250 mL of sample solution and 10 mL of eluent. This procedure has been successfully applied to the determination of copper in different water samples.     

Novel modified carbon nanotubes as a selective sorbent for preconcentration and determination of trace copper ions in fruit samples

In this work, multiwalled carbon nanotubes were reacted with N‐[3‐(triet‐hoxysilyl)propyl]isonicotinamide to prepare pyridine‐functionalized carbon nanotubes. This novel sorbent was characterized by infrared spectroscopy, thermal and elemental analysis, and scanning electron microscopy. Functionalized carbon nanotubes were applied for the preconcentration and determination of copper ions using flame atomic absorption spectrometry. Various parameters such as sample pH, flow rate, eluent type and concentration, and its volume were optimized. Under optimal experimental conditions, the limit of detection, the relative standard deviation, and the recovery of the method were 0.65 ng/mL, 3.2% and 99.4%, respectively. After validating the method using standard reference materials, the new sorbent was applied for the extraction and determination of trace copper(II) ions in fruit samples.     

气相色谱法快速测定儿童驱蚊扣中菊酯类物质

建立快速测定儿童驱蚊扣中菊酯类残留的气相色谱法。以甲醇为萃取溶剂,萃取液经中性氧化铝固相萃取小柱净化,以乙酸乙酯为洗脱溶剂,洗脱液经旋转蒸发浓缩后,用电子捕获检测器检测,外标法定量。8种菊酯类化合物的质量浓度在0.05~1.00 mg/L范围内与色谱峰面积成良好的线性关系,相关系数均大于0.998,检出限为0.48~2.90μg/L。3个加标水平样品的平均回收率为93.8%~119.7%,测定结果的相对标准偏差为0.88%~6.43%(n=5)。该方法样品前处理简便,准确度和精密度良好,可用于驱蚊扣产品中菊酯类物质的检测。