Microwave‐assisted preparation of poly(ionic liquids)‐modified magnetic nanoparticles for pesticide extraction

Novel poly(ionic liquids) were synthesized and immobilized on prepared magnetic nanoparticles, which were used to extract pesticides from fruit and vegetable samples by dispersive solid‐phase extraction prior to high‐performance liquid chromatography analysis. Compared with monomeric ionic liquids, poly(ionic liquids) have a larger effective contact area and higher viscosity, so they can achieve higher extraction efficiency and be used repeatedly without a decrease in analyte recovery. The immobilized poly(ionic liquids) were rapidly separated from the sample matrix, providing a simple approach for sample pretreatment. The nature and volume of the desorption solvent and amount of poly(ionic liquid)‐modified magnetic material were optimized for the extraction process. Under optimum conditions, calibration curves were linear (R² > 0.9988) for pesticide concentrations in the range of 0.100–10.000 μg/L. The relative standard deviations for repeated determinations of the four analytes were 2.29–3.31%. The limits of detection and quantification were 0.29–0.88 and 0.97–2.93 μg/L, respectively. Our results demonstrate that the developed poly(ionic liquid)‐modified material is an effective absorbent to extract pesticides from fruit and vegetable samples.     

High‐throughput microscale extraction using ionic liquids and derivatives: A review

Ionic liquids and derivatives—mainly polymeric ionic liquids and magnetic ionic liquids—have been extensively used in microscale extraction over the past few years. Current trends in analytical sample preparation gear toward linking microextraction approaches with high‐throughput sample processing to comply with green analytical chemistry requirements. A variety of high sample throughput strategies that are coupled to both ionic‐liquid‐based solid‐phase microextraction and ionic liquid‐based liquid‐phase microextraction are herein reported. The review is focused on microscale extraction methods that use (i) custom‐made and dedicated extraction devices, (ii) parallel extraction, (iii) magnetic‐based separation, and (iv) miniaturized systems employing semi‐automatic or fully automatic flow injection methods, related micro/millifluidic devices, and robotic equipment.     

Fe3O4/reduced graphene oxide‐carbon nanotubes composite for the magnetic solid‐phase extraction and HPLC determination of sulfonamides in milk

A novel magnetic adsorbent Fe₃O₄/reduced graphene oxide‐carbon nanotubes, was prepared by one‐pot solvothermal synthesis method. It was characterized by scanning electron microscopy, X‐ray powder diffraction and vibrating sample magnetometry. The diameter of Fe₃O₄ microparticles was about 350 nm, which were covered by carbon nanotubes and reduced graphene oxide sheets, while carbon nanotubes inserted between the reduced graphene oxide sheets effectively prevented their aggregation. The composite had large surface area and good magnetic property, suiting for magnetic solid‐phase extraction and the determination of sulfonamides, by coupling with high‐performance liquid chromatography. Under the optimized conditions (including extraction time, amount of adsorbent, solution pH, ionic strength and desorption conditions), a good linear was achieved in the concentration range of 5–500 μg/L and the low limits of detection and low limits of quantification were 0.35–1.32 and 1.16–4.40 μg/L, respectively. The enrichment factors were estimated to be 24.72 to 30.15 fold. The proposed method was applied for the detection of sulfonamides in milk sample and the recoveries were 88.4–105.9%, with relative standard deviations of 0.74–5.38%.     

Graphene oxide reinforced polymeric ionic liquid monolith solid‐phase microextraction sorbent for high‐performance liquid chromatography analysis of phenolic compounds in aqueous environmental samples

A graphene oxide reinforced polymeric ionic liquids monolith was obtained by copolymerization of graphene oxide doped 1‐(3‐aminopropyl)‐3‐(4‐vinylbenzyl)imidazolium 4‐styrenesulfonate monomer and 1,6‐di‐(3‐vinylimidazolium) hexane bihexafluorophosphate cross‐linking agent. Coupled to high‐performance liquid chromatography, the monolith was used as a solid‐phase microextraction sorbent to analyze several phenolic compounds in aqueous samples. Under the optimized extraction and desorption conditions, linear ranges were 5–400 μg/L for 3‐nitrophenol, 2‐nitrophenol, and 2,5‐dichlorophenol and 2–400 μg/L for 4‐chlorophenol, 2‐methylphenol, and 2,4,6‐trichlorophenol (R² = 0.9973–0.9988). The limits of detection were 0.5 μg/L for 3‐nitrophenol and 2‐nitrophenol and 0.2 μg/L for the rest of the analytes. The proposed method was used to determine target analytes in groundwater from an industrial park and river water. None of the analytes was detected. Relative recoveries were in the range of 75.5–113%.     

Deep eutectic solvents skeleton typed molecularly imprinted chitosan microsphere coated magnetic graphene oxide for solid‐phase microextraction of chlorophenols from environmental water

Novel molecularly imprinted chitosan microspheres were prepared on the surface of magnetic graphene oxide, with deep eutectic solvents both as a functional monomer and template. The prepared molecularly imprinted chitosan microspheres‐magnetic graphene oxide was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area, thermogravimetric analysis were subsequently combined with solid‐phase micro‐extraction for simultaneous separation and enrichment of the extraction of chlorophenols from environmental water. Factors affecting the extraction efficiency of chlorophenols were optimized using response surface methodology. The actual extraction capacities under the optimal conditions (liquid to solid ratio = 3, cycles of adsorption/desorption = 5, 40°C extraction temperature, and extraction time for 35 min) were 86.90 mg/g. Compared to the traditional materials, the molecularly imprinted chitosan microspheres‐magnetic graphene oxide produced higher selectivity and extraction capacity.     

Simultaneous determination of levofloxacin and ciprofloxacin in human urine by ionic‐liquid‐based,dual‐template molecularly imprinted coated graphene oxide monolithic solid‐phase extraction

A novel method was developed to simultaneously determine the ciprofloxacin and levofloxacin levels in human urine using an ionic‐liquid‐based, dual‐molecularly imprinted polymer‐coated graphene oxide solid‐phase extraction monolithic column coupled with high‐performance liquid chromatography. The molecularly imprinted monolithic column was prepared using ciprofloxacin and levofloxacin as templates, 1‐vinyl‐3‐ethylimidazolium bromide as the functional monomer, and graphene oxide as the core material. The resulting imprinted monoliths were characterized by scanning electron microscopy and fourier transform‐infrared spectroscopy. The efficiency and capacity of the ionic‐liquid‐based imprinted monolithic column were investigated by varying the synthesis conditions (ciprofloxacin/levofloxacin ratio and template/functional monomer/cross‐linker ratio). The solid‐phase extraction process was optimized by changing the washing and eluting conditions. The results suggested that the proposed ionic‐liquid‐based molecularly imprinted solid‐phase extraction monolithic‐high‐performance liquid chromatography method could separate ciprofloxacin and levofloxacin efficiently and simultaneously from human urine. The mean recoveries of ciprofloxacin and levofloxacin ranged from 89.2 to 93.8 and 86.7 to 94.6%, respectively. The intra‐ and interday relative standard deviation ranged from 0.9 to 3.2 and 0.8 to 2.9%, respectively. Under the optimized conditions, the recoveries of ciprofloxacin and levofloxacin were more than 93.8%.     

Preparation of magnetic chitosan and graphene oxide-functional guanidinium ionic liquid composite for the solid-phase extraction of protein

A series of novel cationic functional hexaalkylguanidinium ionic liquids and anionic functional tetraalkylguanidinium ionic liquids have been synthesized, and then magnetic chitosan graphene oxide (MCGO) composite has been prepared and coated with these functional guanidinium ionic liquids to extract protein by magnetic solid-phase extraction. MCGO-functional guanidinium ionic liquid has been characterized by vibrating sample magnetometer, field emission scanning electron microscopy, X-ray diffraction spectrometer and Fourier transform infrared spectrometer. After extraction, the concentrations of protein were determined by measuring the absorbance at 278 nm using an ultra violet visible spectrophotometer. The advantages of MCGO-functional guanidinium ionic liquid in protein extraction were compared with magnetic chitosan, graphene oxide, MCGO and MCGO-ordinary imidazolium ionic liquid. The proposed method has been applied to extract trypsin, lysozyme, ovalbumin and bovine serum albumin. A comprehensive study of the adsorption conditions such as the concentration of protein, the amount of MCGO-functional guanidinium ionic liquid, the pH, the temperature and the extraction time were also presented. Moreover, the MCGO-functional guanidinium ionic liquid can be easily regenerated, and the extraction capacity was about 94% of the initial one after being used three times.     

离子液体固定化材料在固相萃取中的应用研究进展

离子液体是由阴、阳离子组成的低温熔融盐,几乎没有蒸汽压,具有稳定性好、溶解能力强、结构可设计、导电性好等优良性能.离子液体作为一种广受关注的新型“绿色溶剂”,具有代替传统有机溶剂的潜力,其制备方法和应用范围研究日趋完善和多样,已广泛应用于催化化学、光电化学、材料化学和分析化学等领域.离子液体通过功能化导向设计后,可以将...     

Quantitative determination of trace phenazopyridine in human urine samples by hyphenation of dispersive solid‐phase extraction and liquid‐phase microextraction followed by gas chromatography/mass spectrometry analysis

Magnetic dispersive solid‐phase extraction followed by dispersive liquid?liquid microextraction coupled with gas chromatography/mass spectrometry was applied for the quantitative analysis of phenazopyridine in urinary samples. Magnetic dispersive solid‐phase extraction was carried out using magnetic graphene oxide nanoparticles modified by poly(thiophene‐pyrrole) copolymer. The eluting solvent of this step was used as the disperser solvent for the dispersive liquid?liquid microextraction procedure. To reach the maximum efficiency of the method, effective parameters including sorbent amount, adsorption time, type and volume of disperser and extraction solvents, pH of the sample solution, and ionic strength as well as desorption time, and approach were optimized, separately. Characterization of the synthesized sorbent was studied by utilizing infrared spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray analysis. Calibration curve was linear in the range of 0.5?250 ng/mL (R² = 0.9988) with limits of detection and quantification of 0.1 and 0.5 ng/mL, respectively. Intra‐ and interday precisions (RSD%, n = 3) of the method were in the range of 4.6?5.4% and 4.0?5.5%, respectively, at three different concentration levels. Under the optimal condition, this method was successfully applied for the determination of phenazopyridine in human urine samples. The relative recoveries were obtained in the range of 85.0?89.0%.     

Preparation of novel ionic‐liquid‐modified magnetic nanoparticles by a microwave‐assisted method for sulfonylurea herbicides extraction

Ionic liquids immobilized on magnetic nanoparticles were prepared by an efficient microwave‐assisted synthesis method, and the properties of the ionic liquids were tuned based on the aromatic functional modification of its anion through a simple metathesis reaction. The novel as‐synthesized magnetic materials were characterized by various instrumental techniques. The magnetic nanoparticles have been utilized as adsorbents for the extraction of four sulfonylurea herbicides in tea samples, in combination with high‐performance liquid chromatography analysis. Significant extraction parameters, including type and volume of desorption solvent, extraction time, amount of adsorbent, and ionic strength were investigated. Under the optimum conditions, good linearity was obtained in the concentration range of 1–150 μg/L for metsulfuron‐methyl and bensulfuron‐methyl, and 3–150 μg/L for sulfometuron‐methyl and chlorimuron‐ethyl, with correlation coefficients R² > 0.9987. Low limits of detection were obtained ranging from 0.13 to 0.81 μg/L. The relative standard deviations were 1.8–3.9%. Comparisons of extraction efficiency with conventional solid‐phase extraction equipped with a commercial C₁₈ cartridge were performed. Results indicated that magnetic solid‐phase extraction is simple, time‐saving, efficient and inexpensive with the reusability of adsorbents. The proposed method has been successfully used to determine sulfonylurea herbicides from tea samples with satisfactory recoveries of 80.5–104.2%.     

One‐pot synthesis of magnetic zeolitic imidazolate framework/grapheme oxide composites for the extraction of neonicotinoid insecticides from environmental water samples

Magnetic zeolitic imidazolate framework 67/graphene oxide composites were synthesized by one‐pot method at room temperature for the first time. Electrostatic interactions between positively charged metal ions and both negatively charged graphene oxide and Fe₃O₄ nanoparticles were expected to chemically stabilize magnetic composites to generate homogeneous magnetic products. The additional amount of graphene oxide and stirring time of graphene oxide, Co²⁺, and Fe₃O₄ solution were investigated. The zeolitic imidazolate framework 67 and Fe₃O₄ nanoparticles were uniformly attached on the surface of graphene oxide. The composites were applied to magnetic solid‐phase extraction of five neonicotinoid insecticides in environmental water samples. The main experimental parameters such as amount of added magnetic composites, extraction pH, ionic strength, and desorption solvent were optimized to increase the capacity of adsorbing neonicotinoid insecticides. The results show limits of detection at signal‐to‐noise ratio of 3 were 0.06–1.0 ng/mL under optimal conditions. All analytes exhibited good linearity with correlation coefficients of higher than 0.9915. The relative standard deviations for five neonicotinoid insecticides in environmental samples ranged from 1.8 to 16.5%, and good recoveries from 83.5 to 117.0% were obtained, indicating that magnetic zeolitic imidazolate framework 67/graphene oxide composites were feasible for analysis of trace analytes in environmental water samples.     

基于碳基磁性材料的磁固相萃取技术在食品分析应用中的研究进展

食品中残留的痕量有毒物质严重威胁人体健康,对其进行分析十分必要。然而,食品中有毒物质种类多、量少、基质复杂,需选择适当的样品预处理技术进行提取和净化。磁固相萃取(MSPE)因具有操作简单、省时快速、无需离心过滤、环境友好等优点,被认为是一种高效的样品预处理技术并应用于食品分析中。MSPE中使用的磁性吸附剂的吸附容量和选择性是影响MSPE萃取效率和选择性高低的关键,对所建立分析方法的准确度起着关键作用。碳基磁性材料是具有价格低廉、来源丰富、比表面积大、化学稳定性好、吸附容量高、绿色环保等优点的一类新型功能性磁性材料,可以富集不同性质的有机、无机分析物,在环境分析、生物检测、污染治理等多个领域取得了较大进展。近年来,基于碳基磁性材料的MSPE技术在食品分析预处理领域逐渐得到应用,但尚处于起步阶段,存在巨大的应用潜力。该文以碳基类别(碳纳米管、石墨烯、金属有机骨架衍生碳、活性炭等)为主线,综述了采用MSPE技术,以碳基磁性材料为吸附剂,对食品样品中酯类、真菌毒素、多环芳烃、抗生素、生物碱、酚类、维生素、抗菌药等物质进行萃取,进而采用液相色谱法等进行分析的应用实例,同时阐述了该技术存在的问题,并对其发展方向做出了展望。该综述将为基于碳基磁性材料的MSPE技术在食品分析中的广泛应用提供理论依据和技术支撑。     

Facile preparation of magnetic graphene oxide/nanoscale zerovalent iron adsorbent for magnetic solid‐phase extraction of ultra‐trace quinolones in milk samples

A simple pH‐responsive magnetic solid‐phase extraction method was developed using graphene oxide–coated nanoscale zerovalent iron nanoparticles as an efficient adsorbent prior to high‐performance liquid chromatography‐tandem mass spectrometry for determination of ultra‐trace quinolones in milk samples. Various parameters affecting maghemite synthesis and separation such as pH of sample solution, amount of magnetic adsorbent, eluent type, and volume were optimized. The limits of detection are from 3.1 to 13.3 ng/L. The intra‐ and interprecision values are in the range of 2.9–6.9% and 7.6–15.1%, respectively. Recoveries are from 82.4 to 103.9%. Therefore, this simple and sensitive method is suitable for detecting ultra‐trace quinolone residues in milk.     

Development and validation of a magnetic solid‐phase extraction with high‐performance liquid chromatography method for the simultaneous determination of amphetamine and methadone in urine

The simultaneous determination of amphetamine and methadone was carried out by magnetic graphene oxide nanoparticles, a magnetic solid‐phase extraction adsorbent, as a new sample treatment technique. The main factors (the amounts of sample volume, amount of adsorbent, type and amount of extraction organic solvent, time of extraction and desorption, pH, the ionic strength of extraction medium, and agitation rate) influencing the extraction efficiency were investigated and optimized. Under the optimized conditions, good linearity was observed in the range of 100–1500 ng/mL for amphetamine and 100–1000 ng/mL for methadone. The method was evaluated for determination of AM and methadone in positive urine samples, satisfactory results were obtained, therefore magnetic solid‐phase extraction can be applied as a novel method for the determination of drugs of abuse in forensic laboratories.     

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.     

Microwave‐assisted preparation of poly(ionic liquids)‐modified polystyrene magnetic nanospheres for phthalate esters extraction from beverages

The fabrication of novel poly(ionic liquids)‐modified polystyrene (PSt) magnetic nanospheres (PILs‐PMNPs) by a one‐pot miniemulsion copolymerization reaction was achieved through an efficient microwave‐assisted synthesis method. The morphology, structure, and magnetic behavior of the as‐prepared magnetic materials were characterized by using transmission electron microscopy, vibrating sample magnetometry, etc. The magnetic materials were utilized as sorbents for the extraction of phthalate esters (PAEs) from beverage samples followed by high‐performance ultrafast liquid chromatography analysis. Significant extraction parameters that could affect the extraction efficiencies were investigated particularly. Under optimum conditions, good linearity was obtained in the concentration range of 0.5–50 (dimethyl phthalate), 0.3–50 (diethyl phthalate), 0.2–50 (butyl benzyl phthalate), and 0.4–50 μg/L (di‐n‐butyl phthalate), with correlation coefficients R ² > 0.9989. Limits of detection were in the range 125–350 pg. The proposed method was successfully applied to determine PAEs from beverage samples with satisfactory recovery ranging from 77.8 to 102.1% and relative standard deviations ranging from 3.7 to 8.4%. Comparisons of extraction efficiency with PSt‐modified MNPs as sorbents were performed. The results demonstrated that PILs‐PMNPs possessed an excellent adsorption capability toward the trace PAE analytes.     

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.     

Dicationic polymeric ionic‐liquid‐based magnetic material as an adsorbent for the magnetic solid‐phase extraction of organophosphate pesticides and polycyclic aromatic hydrocarbons

Magnetic particles modified with a dicationic polymeric ionic liquid are described as a new adsorbent in magnetic solid‐phase extraction. They were obtained through the copolymerization of a 1,8‐di(3‐vinylimidazolium)octane‐based ionic liquid with vinyl‐modified SiO₂@Fe₃O₄, and were characterized by FTIR spectroscopy, X‐ray diffraction, and vibrating sample magnetometry. The modified magnetic particles are effective in the extraction of organophosphate pesticides and polycyclic aromatic hydrocarbons. Also, they can provide different extraction performance for the selected analytes including fenitrothion, parathion, fenthion, phoxim, phenanthrene, and fluoranthene, where the extraction efficiency is found to be in agreement with the hydrophobicity of analytes. Various factors influencing the extraction efficiency, such as, the amount of adsorbent, extraction, and desorption time, and type and volume of the desorption solvent, were optimized. Under the optimized conditions, a good linearity ranging from 1–100 μg/L is obtained for all analytes, except for parathion (2–200 μg/L), where the correlation coefficients varied from 0.9960 to 0.9998. The limits of detection are 0.2–0.8 μg/L, and intraday and interday relative standard deviations are 1.7–7.4% (n = 5) and 3.8–8.0% (n = 3), respectively. The magnetic solid‐phase extraction combined with high‐performance liquid chromatography can be applied for the detection of trace targets in real water samples with satisfactory relative recoveries and relative standard deviations.     

Ionic‐liquid‐based dispersive liquid–liquid microextraction combined with magnetic solid‐phase extraction for the determination of aflatoxins B1, B2, G1, and G2 in animal feeds by high‐performance liquid chromatography with fluorescence detection

A novel two‐step extraction technique combining ionic‐liquid‐based dispersive liquid–liquid microextraction with magnetic solid‐phase extraction was developed for the preconcentration and separation of aflatoxins in animal feedstuffs before high‐performance liquid chromatography coupled with fluorescence detection. In this work, ionic liquid 1‐octyl‐3‐methylimidazolium hexafluorophosphate was used as the extractant in dispersive liquid–liquid microextraction, and hydrophobic pelargonic acid modified Fe₃O₄ magnetic nanoparticles as an efficient adsorbent were applied to retrieve the aflatoxins‐containing ionic liquid. Notably, the target of magnetic nanoparticles was the ionic liquid rather than the aflatoxins. Because of the rapid mass transfer associated with the dispersive liquid–liquid microextraction and magnetic solid phase steps, fast extraction could be achieved. The main parameters affecting the extraction recoveries of aflatoxins were investigated and optimized. Under the optimum conditions, vortexing at 2500 rpm for 1 min in the dispersive liquid–liquid microextraction and magnetic solid‐phase extraction and then desorption by sonication for 2 min with acetonitrile as eluent. The recoveries were 90.3–103.7% with relative standard deviations of 3.2–6.4%. Good linearity was observed with correlation coefficients ranged from 0.9986 to 0.9995. The detection limits were 0.632, 0.087, 0.422 and 0.146 ng/mL for aflatoxins B₁, B2, G1, and G2, respectively. The results were also compared with the pretreatment method carried out by conventional immunoaffinity columns.     

Preparation of arginine‐modified reduced graphene oxide composite filled in an on‐line solid‐phase extraction disk and its application in the analysis of heterocyclic aromatic amines

An arginine‐modified reduced graphene oxide composite was prepared in an on‐line solid‐phase extraction disk and coupled to high‐performance liquid chromatography for the re‐enrichment of heterocyclic aromatic amines. The synthetic composite presented an excellent adsorption capability because of the ultrahigh active surface area of graphene and the abundant alkaline groups of arginine. The adsorption capacity of it was 52.7 mg 2‐amino‐3‐methyl‐imidazo[4,5‐f]‐quinoline per gram, nearly twice that of threonine‐modified reduced graphene oxide composite, glutamic acid modified reduced graphene oxide composite, and reduced graphene oxide. This on‐line method was successfully applied to the detection of a series of heterocyclic aromatic amines in beef jerky. After clean‐up and re‐enrichment of the on‐line solid‐phase extraction disk, the chromatographic background of the sample was low and the shape of chromatographic peaks was sharp. The method detection limit was in the range of 0.30–0.49 ng/g, and the recovery was in the range of 82.0–111.5%.