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

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

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

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

Pipette‐tip solid‐phase extraction based on deep eutectic solvent modified graphene for the determination of sulfamerazine in river water

A green and novel deep eutectic solvent modified graphene was prepared and used as a neutral adsorbent for the rapid determination of sulfamerazine in a river water sample by pipette‐tip solid‐phase extraction. Compared with conventional graphene, deep eutectic solvent modified graphene can change the surface of graphene with wrinkled structure and higher selective extraction ability. The properties of deep eutectic solvent modified graphene and graphene were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Static adsorption showed deep eutectic solvent modified graphene had a higher adsorption ability (18.62 mg/g) than graphene. Under the optimum conditions, factors such as kinds of washing solvents and elution solvents and volume of elution solvent were evaluated. The limits of detection and quantification were 0.01 and 0.03 μg/mL, respectively. The method recoveries of sulfamerazine were in the range of 91.01–96.82% with associated intraday relative standard deviations ranging from 1.63 to 3.46% and interday relative standard deviations ranging from 0.68 to 3.84%. Deep eutectic solvent modified graphene showed satisfactory results (recovery was 95.38%) and potential for rapid purification of sulfamerazine in river water sample in combination with the pipette‐tip solid‐phase extraction method.     

Polyethyleneimine‐modified porous aromatic framework and silane coupling agent grafted graphene oxide composite materials for determination of phenolic acids in Chinese Wolfberry drink by HPLC

A simple method for the determination of phenolic acids in Chinese Wolfberry drink based on polyethyleneimine modified porous aromatic framework and graphene oxide composite sorbent for pipette‐tip solid‐phase extraction was developed. Porous aromatic framework and raphene oxide composite materials were grafted by silane coupling agent (3‐Chloropropyl)‐trimethoxysilane. The modified materials were characterized by five kinds of characterization. Experimental results showed that the prepared p‐phenylenediamine, cyanuric chloride, and graphene oxide composite material had a loose structure combined with the framework which improved hydrophobicity, and polyethyleneimine to increase the selectivity with the targets. The parameters of the pipette‐tip solid‐phase extraction procedure including the amount of sorbents, volumes and types of washing solvents and elution solvents were optimized to achieve optimal extraction efficiency. Good linearity of best material was achieved in the range of 0.1–400 µg/mL with correlation coefficient of chlorogenic acid (0.9994), caffeic acid (0.9997), and ferulic acid (0.9998). Recoveries between 93.5 and 102.3% were obtained at three spiked levels with relative standard deviation ≤3.1%. The proposed method was successfully applied for the determination of phenolic acids in Chinese Wolfberry drink sample.     

Activated carbon cloth filled pipette tip for solid phase extraction of nickel(II), lead(II), cadmium(II), copper(II) and cobalt(II) as 1,3,4-thiadiazole-2,5-dithiol chelates for ultra-trace detection by FAAS

A solid phase extraction method is established for preconcentration of nickel, lead, cadmium, copper and cobalt using pipette tip solid phase extraction. The presented process was dependent on chelation of analytes with 1,3,4-thiadiazole-2,5-dithiol, then allowing the solution to flow through an activated carbon cloth packed pipette tip. The adsorbed metal chelates on the surface of activated carbon cloth were eluted by 5 mL of 3 M HNO₃. The concentrations of nickel, lead, cadmium, copper and cobalt were detected using a flame atomic absorption spectrometer (FAAS). The pipette tip solid phase extraction exhibit a preconcentration factor of 120. The limit of detection values were 2.7, 1.7, 1.3, 2.0 and 2.9 µg L^?1 for Ni(II), Pb(II), Cd(II), Cu(II) and Co(II), respectively. Validation of the method was checked by the analysis of TMDA-53.3 and TMDA-64.2 certified reference materials. The method was successfully applied for water and fertiliser samples.     

Optimization of heteroatom doped graphene oxide by deep eutectic solvents and the application for pipette‐tip solid‐phase extraction of flavonoids

In order to improve the permeation and adsorption properties of graphene oxide, heteroatoms and deep eutectic solvent were introduced in this study. After being modified, the structural properties of graphene oxide were improved and the materials were applied to the determination of myricetin and rutin in tea sample by pipette‐tip solid‐phase extraction method. The materials were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐Ray diffractomer, energy dispersive spectroscopy, atomic force microscope, and specific surface area by Brunauer–Emmett–Teller N₂ adsorption desorption analysis. Meanwhile, they were tested by static and dynamic adsorption. The result showed that the materials after modifying had better adsorption amount for myricetin and rutin than graphene oxide. The calibration graphs of myricetin and rutin in MeOH were linear over 0.10–500.00 µg/mL, and the limits of detection and quantification were in the range of 0.00546–0.0182 µg/mL and 0.00741–0.0247 µg/mL, respectively. A reliable analytical method was developed for recognition targets in tea sample by DES modified nitrogen‐doped graphene oxide with satisfactory extraction recoveries (myricetin 99.77%, rutin 98.14%). It was potential for the rapid purification of myricetin and rutin in tea sample combined with the pipette‐tip solid‐phase extraction.     

样品制备与处理的进展——无溶剂萃取技术

本文讨论了现代分析化学的重要领域之一, 样品制备及前处理技术的进展--无溶剂萃取技术。包括气相萃取、超临界流体萃取、膜萃取、固相萃取、固相微萃取等方法。简述了这些方法的原理及其应用, 探讨了样品制备与前处理技术的发展动向。     

Fabrication of boronate‐decorated polyhedral oligomeric silsesquioxanes grafted cotton fiber for the selective enrichment of nucleosides in urine

Various cotton fiber based boronate‐affinity adsorbents are recently developed for the sample pretreatment of cis‐diol‐containing biomolecules, but most do not have efficient capacity due to limited binding sites on the surface of cotton fibers. To increase the density of boronate groups on the surface of cotton fiber, polyhedral oligomeric silsesquioxanes were used to modify cotton fiber to provide plentiful reactive sites for subsequent functionalization with 4‐formylphenylboronic acid. The new adsorbent showed special recognition ability towards cis‐diols and high adsorption capacity (175 μg/g for catechol, 250 μg/g for dopamine, 400 μg/g for adenosine). The in‐pipette‐tip solid‐phase extraction was investigated under different conditions, including pH and ionic strength of solution, adsorbent amount, pipette times, washing solvent, and elution solvent. The in‐pipette‐tip solid‐phase extraction coupled with high‐performance liquid chromatography was used to analyze four nucleosides in urine samples. Under the optimal extraction conditions, the detection limits were determined to be between 5.1 and 6.1 ng/mL (S/N  =  3), and the linearity ranged from 20 to 500 ng/mL for these analytes. The accuracy of the analytical method was examined by studying the relative recoveries of analytes in real urine samples with recoveries varying from 83 to 104% (RSD = 3.9–10.2%, n = 3).     

Graphene‐based pipette tip solid‐phase extraction with ultra‐high performance liquid chromatography and tandem mass spectrometry for the analysis of carbamate pesticide residues in fruit juice

Graphene‐based pipette tip solid‐phase extraction was combined with ultra‐high performance liquid chromatography and tandem mass spectrometry for the determination of carbamate pesticide residues in fruit juice samples. Four milligrams of graphene was used as sorbent material to pack a 1000 μL pipette tip for the extraction of pirimicarb, propoxur, isoprocarb, fenobucarb, and diethofencarb from 3 mL of fruit juice sample. The whole extraction process was finished in 12 min, and the volume of eluent used was only 1.5 mL. Under the optimized conditions, good linear relationship (R > 0.999) and lower limits of detection (0.0022–0.033 ng/mL) were achieved. The recoveries at three spiked levels ranged from 80.90 to 124.60% with relative standard deviations less than 4.88%. Compared with commercially available sorbents including propylsulfonic acid silica, graphitized carbon black, and C₁₈, graphene was superior in extraction efficiency. The proposed method is simple, rapid, sensitive, selective, and solvent saving.     

Preparation of an acryloyl β‐cyclodextrin‐silica hybrid monolithic column and its application in pipette tip solid‐phase extraction and HPLC analysis of methyl parathion and fenthion

An acryloyl β‐cyclodextrin‐silica hybrid monolithic column for pipette tip solid‐phase extraction and high‐performance liquid chromatography determination of methyl parathion and fenthion has been prepared through a sol–gel polymerization method. The synthesis conditions, including the volume of cross‐linker and the ratio of inorganic solution to organic solution, were optimized. The prepared monolithic column was characterized by thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The eluent type, volume and flow rate, sample volume, flow rate, acidity, and ionic strength were optimized in detail. Under the optimized conditions, a simple and sensitive pipette tip solid‐phase extraction with high‐performance liquid chromatography method was developed for the determination of methyl parathion and fenthion in lettuce. The method yielded a linear calibration curve in the concentration ranges of 15–400 μg/kg for methyl parathion and 20–400 μg/kg for fenthion with correlation coefficients of above 0.9957. The limits of detection were 4.5 μg/kg for methyl parathion and 6.0 μg/kg for fenthion, respectively. The recoveries of methyl parathion and fenthion spiked in lettuce ranged from 96.0 to 104.2% with relative standard deviations less than 8.4%.     

Sulfonated poly(styrene‐divinylbenzene) modified with amines and the application for pipette‐tip solid‐phase extraction of carbendazim in apples

Sulfonated poly(styrene‐divinylbenzene) modified with five kinds of amine functional groups was applied to the determination of carbendazim in apple samples with a pipette‐tip solid‐phase extraction method. The structures of the polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Five different modifications of the solid‐phase extraction sorbent based on sulfonated poly(styrene‐divinylbenzene) were tested under static and pipette‐tip solid‐phase extraction conditions. The polymer modified with p‐methoxyaniline showed the best recognition capacity and adsorption amount for carbendazim. Under the optimum conditions, 3.00 mg of the adsorbent, 1.00 mL of ethyl acetate as washing solvent, and 1.00 mL of ammonia/acetonitrile (5:95, v/v) as elution solvent were used in the pretreatment procedure of apple samples. The calibration graphs of carbendazim in methanol were linear over 5.00–200.00 μg/mL, and the limits of detection and quantification were 0.01 and 0.03 μg/mL, respectively. The method recoveries of carbendazim were in the range of 91.31–98.13% with associated intraday relative standard deviations of 0.76–2.13% and interday relative standard deviations of 1.10–1.85%. Sulfonated poly(styrene‐divinylbenzene) modified with p‐methoxyaniline showed satisfactory results (recovery: 97.96%) and potential for the rapid purification of carbendazim in apple samples combined with the pipette‐tip solid‐phase extraction.     

Miniaturized pipette‐tip‐based electrospun polyacrylonitrile nanofibers for the micro‐solid‐phase extraction of nitro‐based explosive compounds

In this study, a self‐assembly of miniaturized pipette‐tip‐based solid‐phase extraction for the simultaneous extraction of nitroaromatic compounds was developed, with electrospun polyacrylonitrile nanofibers used as sorbents. The electrospun polyacrylonitrile nanofibers were characterized by scanning electron microscopy, FTIR analysis and surface area analysis. Good linearities for the four nitroaromatic compounds (2,6‐dinitrotoluene, 2‐nitrotoluene, 3‐nitrotoluene, and 4‐nitrotoluene) were obtained in a range of 250–1000 μg/L with coefficients of determination > 0.99. The limits of detection of these analytes were between 21 and 38 μg/L. The results showed that the pipette‐tip‐based solid‐phase extraction was effective in extracting nitrotoluenes in the pH regime of environmental interest (≈ 6). The investigation also revealed that the optimum mass of electrospun polyacrylonitrile nanofibers sorbent was 15 mg and 20 aspirating/dispensing cycles gave the maximum recovery of nitrotoluenes with 200 μL acetonitrile as the best eluting solvent. Moreover, the performance of the present method was studied for the extraction and determination of nitroaromatic compounds in real environmental water samples and good recoveries ranging from 70 to 115% were found, and respective relative standard deviations of <12% were obtained.     

微波辅助提取-固相膜萃取测定水体沉积物中的甲基汞

利用微波辅助提取-固相膜萃取前处理技术分离富集水体沉积物中的甲基汞,固相膜萃取的前处理方法能够集富集和净化为一体,有效地去除基质的影响。方法的关键在于样品的萃取过程,萃取过程中既要保证样品中甲基汞的原来形态不被破坏和转化,又要保证其从样品中被充分萃取以达到稳定可靠的回收效果。通过微波辅助提取技术将水体沉积物中的甲基汞提取到溶液后,提取液通过0.01%的二乙基二硫代氨基甲酸钠改性后的C18固相萃取膜,选择性地将提取液中的甲基汞分离富集的同时净化。洗脱液再经过原子荧光光谱仪进行测定。实验条件考察了流动相、微波提取条件以及固相膜萃取条件对甲基汞的影响。在最优的实验条件下,对甲基汞的稳定性进行了研究,实验结果表明在4 ℃以及-15 ℃条件下贮存,甲基汞降解不显著。同时对沉积物实际样品和加标样品进行了分析,所得结果沉积物中甲基汞检出限为0.20 μg/kg,沉积物实际样品的加标回收率和相对标准偏差分别在71.3%～87.6%和2.00%~6.36%之间,实验结果令人满意。该方法萃取速度快、消耗溶剂少、萃取效率高,可以同时处理多个样品,节约能耗,绿色环保,符合现代监测分析的发展趋势,适用于分析测定水体沉积物中的甲基汞。     

Determination of Explosives in Water Using Disposable Pipette Extraction and High Performance Liquid Chromatography

The use of disposable pipette extraction was examined for the simple and rapid determination of seven high explosives (cyclotrimethyl-enetrinitramine, cyclotetramethyl-enetetranitramine, 2,4,6-trinitrophenyl-methylnitramine, 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, nitroglycerin, and pentaerythritol tetranitrate) in water. The current study involved the determination of slightly polar and nonpolar explosives in water with a reversed phase sorbent followed by high performance liquid chromatography. The method was based on a styrene divinylbenzene sorbent loosely placed inside a 5-mL pipette tip. Water samples were drawn into the tip and mixed with the sorbent. Air bubbles were also drawn through the tip following sample solution to enhance mixing. Because disposable pipette extraction uses small amounts of sorbent, minimal solvent is required to elute analytes and solvent evaporation is not necessary. The method provided rapid sample preparation, and required less than five minutes to extract 1.0 mL of water sample in the current study. Matrix-matched calibration was performed, and the limits of detection (LOD) were determined to be below 0.1 µg mL^?1 for all targeted explosives in water with an enrichment factor of two. Coefficients of determination (r²) were greater than 0.9990 for all studied explosives, and the recoveries ranged from 69.76% to 87.51%, 83.77% to 91.25%, and 83.62% to 98.99% for samples spiked at 0.25 µg mL^?1, 1.0 µg mL^?1, and 5.0 µg mL^?1, respectively. The relative standard deviations of recoveries at all spiked levels were below 8.97%. These results indicate that the disposable pipette extraction method provided good accuracy and precision for the determination of explosives in water.     

基于电纺纳米纤维的固相萃取技术

纳米纤维极具优越固相萃取介质的潜质,基于纳米纤维的固相萃取法( Nanofibers based solid phase extraction, NFs-SPE)已成为新兴的样品预处理技术。本文在评述NFs-SPE在食品、环境样品、生物样品等实际样品检测应用的相关研究基础上,提出纳米纤维的分子结构和形态结构与目标物吸附效能之间存在着“结构”-“效应”关系,这将是明确纳米纤维高效吸附目标物的机理的关键突破口。     

分子印迹样品前处理技术的研究进展

样品前处理是分析过程的关键环节,直接影响着分析结果的准确度和精密度．分子印迹聚合物具有特异性识别能力,能从复杂样品中选择性分离富集目标物,在复杂样品前处理领域中有重要的发展潜力和应用前景．本文综述了近年来分子印迹样品前处理技术的研究进展,包括分子印迹固相萃取、分子印迹固相微萃取、分子印迹膜萃取等样品前处理技术．     

Solid phase extraction conditions for the selective isolation of drugs from biological fluids predicted using liquid chromatography

Summary A new method to predict the most suitable conditions for the solid phase extraction of 1,4-benzodiazepines and related compounds using C18 Sep-Pak carridges is proposed. The composition of the washing and elution solvents for the solid phase extraction of a test compound can be obtained from its capacity factor on a C18 HPLC column and an equation which relates capacity factors and solid phase extraction data of other similar compounds. The solid phase extraction data given in this paper can be used by others, there by saving considerable time and effort in the development of sample preparation methods. The suitability of the method was checked with two test compounds, showing good results.     

Determination of Atrazine,Simazine, Alachlor,and Metolachlor in Surface Water Using Dispersive Pipette Extraction and Gas Chromatography–Mass Spectrometry

Four commonly found pesticides (alachlor, atrazine, metolachlor, and simazine) in surface water were determined using dispersive pipette extraction followed by gas chromatography–mass spectrometry. The rapid mixing and equilibrium between the dispersive pipette extraction adsorbent and water sample resulted in fast and efficient extraction. Using only 5?mL of water sample, the estimated time consumption for extraction of each sample was less than 5?min. Method validation was performed to evaluate accuracy, precision, linearity, the limits of detection, and the limits of quantitation. Average recovery of above 90% was obtained with relative standard deviations below 10%, which indicated good accuracy and precision of the dispersive pipette extraction method. Coefficients of determination were all above 0.9901 and showed good linearity. For the four pesticides studied using the current method, the limits of detection ranged from 7 to 40?ng?L^?1, and limits of quantitation were from 20 to 130?ng?L^?1. Method validation results supported the application of the current method for drinking water safety monitoring per National Primary Drinking Water Regulations established by the US Environmental Protection Agency. Water samples from Lake Lanier and Stone Mountain Lake (Georgia, USS) were analyzed with this method as a preliminary work for a larger scale drinking water quality study in the future. Trace amounts of simazine and atrazine were found in lake water samples, but both were below the regulation levels of the US Environmental Protection Agency.     

水中有机污染物前处理方法进展

综述了水样中有机污染物前处理方法的进展情况；重点介绍液-液萃取、固相萃取、液相微萃取、膜萃取和顶空处理技术5种前处理方法的一些基本情况及其优缺点。     

分子印迹聚合物固相萃取研究进展

对最新报道的分子印迹聚合物作为固相萃取剂及其在色谱样品前处理方面的应用进行综述和展望,主要包括固相萃取、基质固相分散萃取、固相微萃取、搅拌棒吸附萃取和磁性材料萃取,同时总结了分子印迹聚合物制备技术面临的挑战和问题,提出了可能的解决方案。