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Chinese Journal of Chromatography
2022, Vol. 40, No. 11
Online: 08 November 2022

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Recent advances in the use of graphene for sample preparation FENG Juanjuan, SUN Mingxia, FENG Yang, XIN Xubo, DING Yali, SUN Min 2022, 40 (11):  953-965.  DOI: 10.3724/SP.J.1123.2022.07012 Abstract ( 167 )   HTML ( 37 )   PDF (2261KB) ( 110 )   Supporting Information Sample preparation is playing an increasingly important role in sample analysis. The enrichment efficiency of the target and the removal effect of the sample matrix are strongly dependent on the extraction material. Therefore, the development of efficient extraction materials is an important research focus in the field of sample preparation. Various advanced materials such as nanomaterials, mesoporous materials, ionic liquids, aerogels, carbon materials, metal-organic frameworks, and covalent organic frameworks have been introduced to produce a diverse range of extraction materials for sample preparation. Owing to its unique physical and chemical properties, graphene, an excellent carbon nanomaterial, has attracted significant attention in different areas. Due to their unique advantages of large surface area, large π-electrons, excellent adsorption properties, abundant functional groups, and facile chemical modification, graphene-based materials have displayed excellent extraction performance for diverse analytes. Furthermore, graphene-based extraction materials have been applied to pretreat real samples from different fields. This paper provides an overview of the recent advances in graphene sample preparation from 2020 to date. The manuscript covers the use of graphene, graphene oxide, and the related functionalized materials as sorbents, as well as their specific applications in cartridge solid-phase extraction, dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fiber solid-phase microextraction, and in-tube solid-phase microextraction. To prevent the aggregation of graphene, three-dimensional graphene, porous graphene aerogels, graphene-modified silica, and stainless-steel mesh were developed for cartridge solid-phase extraction. Furthermore, some graphene-based extraction materials were used to develop online solid-phase extraction, which allowed for automatic and high-throughput tests. Graphene nanosheets and their hybrid materials with molybdenum disulfide or zinc oxide nanoparticles have been applied to dispersive solid-phase extraction, and several types of contaminants, including metal ions, bisphenol endocrine disruptors, paraben preservatives, and phthalates, could be captured. By combination with magnetic materials using the coprecipitation method or via chemical post-modification, many magnetic graphene extraction materials have been produced for magnetic solid-phase extraction. The introduction of magnetic graphene not only enhanced the extraction efficiency but also simplified the test process, making it highly suitable for complex samples such as food and biological samples. Similar to magnetic solid-phase extraction, stir bar sorptive extraction is a very simple and efficient extraction method that shows good extraction performance for metal ions and organic pollutants from environmental water, medicines in urine, and organic pollutants in cosmetics. In addition to its excellent applicability to solid-phase extraction, graphene delivered satisfactory performance for solid-phase microextraction. Graphene has been used as an extraction coating for the extraction of fibers or tubes by coupling solid-phase microextraction with chromatographic detection, and many kinds of organic pollutants, including polychlorinated biphenyls, phthalates, polycyclic aromatic hydrocarbons, toluene, xylenes, organophosphorus pesticides, phenoxy acid herbicides, and antibiotics, in environmental or biological samples have been successfully determined. The extraction mechanism, including π-π, electrostatic, hydrophobic, hydrophilic, and hydrogen-bonding interactions, is also discussed. Because of the mixed-mode interactions and rich functionalization, graphene-based extraction materials could effectively capture and selectively enrich different types of species. These extraction or microextraction techniques have been coupled with detection methods such as chromatography, mass spectrometry, and atomic absorption spectroscopy and widely used in environmental monitoring, food safety, and biochemical analysis. The future development of graphene in the field of sample pretreatment focuses on the following aspects: 1) functionalization of graphene with specific groups such as affinity groups, chelating groups, and molecularly imprinted sites to achieve unique extraction selectivity; 2) combination of graphene with the advanced materials, including covalent organic frameworks, metal organic frameworks, aerogels, and nanomaterials, thus realizing the complementary advantages between materials, so that the hybrid graphene materials find broad application prospects in sample preparation; 3) combination of electromagnetic materials with graphene to form electromagnetic composites, as well as the use of electromagnetic fields to improve extraction selectivity and efficiency; 4) exploiting the good performance of graphene-based materials to overcome the difficulty encountered in the pretreatment of complex samples; 5) development of more green methods to prepare graphene-based extraction materials or functionalize graphene, in line with the trends in green chemistry; 6) application of more graphene-based materials to online sample preparation for meeting the development trends in the field of analytical chemistry.

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Advances in enrichment and separation of cis-diol-containing compounds by porous organic frameworks ZHANG An, ZHANG Juan 2022, 40 (11):  966-978.  DOI: 10.3724/SP.J.1123.2022.04024 Abstract ( 221 )   HTML ( 30 )   PDF (6385KB) ( 95 )   The design and synthesis of boronate affinity materials that show high efficiency, high selectivity, and high enrichment performance have gained significant attention. The principle of boronate affinity relies on the reversible covalent reactions, including the formation of stable five-membered or six-membered cyclic esters with cis-diol-containing compounds in alkaline aqueous media and dissociation of cyclic esters in an acidic surrounding to release cis-diol-containing compounds. Recently, various boronate affinity materials have been synthesized and utilized for selective enrichment of these compounds. Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have been widely used in chromatographic separation and sample pretreatment because of their adjustable pore size, high porosity, high specific surface area, tunable skeleton structure, and favorable chemical and thermal stability. To promote the enrichment selectivity of MOFs and COFs for cis-diol-containing compounds, boronic acid-functionalized MOFs and COFs with various structures and categories have been synthesized. This review summarizes more than 80 investigations into the categories, synthetic strategies, and applications of boronic acid-functionalized MOFs and COFs from the Science Citation Index. These synthesis methods include metal ligand-fragment co-assembly, post-synthetic modification, and bottom-up modification of boronic acid-functionalized porous materials. Although two modification strategies (post-synthetic and metal ligand-fragment co-assembly) have been introduced for the preparation of boronic acid-functionalized MOFs, the latter is more commonly adopted as it improves the enrichment selectivity and enrichment efficiency of MOFs. The common limitations of MOFs such as aggregation and aperture issues were also resolved. Boron affinity MOFs possessing favorable properties according to the characteristics of cis-diol-containing compounds, have also been synthesized. Furthermore, to facilitate enrichment and separation, many boronic acid-functionalized magnetic material MOFs have been developed for the enrichment and analysis of cis-diol-containing compounds. Additionally, the luminescent properties of Ln-MOFs have been used in combination with boronic acid affinity for the enrichment, separation, and subsequent detection of cis-diol-containing compounds. Post-synthetic modification and the bottom-up strategy are the primary methods for the preparation of boronic acid-functionalized COFs. Boronic acid-functionalized COFs are less investigated than boronic acid-functionalized MOFs, likely due to the greater complexity of COF synthesis. This work aims to summarize the research advances, synthesis ideas, and synthesis methods related to boric acid-functionalized porous organic frameworks, which will provide theoretical guidance and technical support for its applications while accelerating the commercialization of such organic frameworks.

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Magnetic ion imprinting techniques for the separation and analysis of elemental speciation PAN Yifan, ZHANG Feng, GAO Wei, SUN Yuelun, ZHANG Sen, LIAN Hongzhen, MAO Li 2022, 40 (11):  979-987.  DOI: 10.3724/SP.J.1123.2022.07013 Abstract ( 71 )   HTML ( 22 )   PDF (1135KB) ( 35 )   Metal and metalloid elements have various possible isotopic compositions and oxidation states and often form coordination or covalent compounds with inorganic and organic small molecules or biological macromolecules, resulting in complex elemental speciation. Different species of the same element often have different properties, which dictate their behavior. Thus, elemental speciation analysis is vital for comprehensively and accurately assessing an element’s environmental and biological effects and the corresponding risks. Because elemental speciation determines the behavior of an element in different environmental and biological processes, the analysis of elemental species has, in recent years, been important in various subjects, including analytical chemistry, environmental chemistry, geochemistry, ecology, agronomy, and biomedicine. The complexity of environmental and biological sample matrices, as well as the multiformity, low levels, and lability of chemical forms pose severe challenges in elemental speciation analysis. Therefore, the highly selective identification and efficient separation of native species is necessary for conducting the identification, quantification, ecotoxicity evaluation, and physiological function study of elemental speciation. Sample pretreatment by solid-phase extraction is an effective solution to the aforementioned problems, but the existing methods do not meet the requirements of current research. The transition of the target species from pre-processing to the detection device includes both on- and off-line arrangements. Compared with the on-line approach, the off-line approach requires more manual participation, increasing the analysis workload. However, the off-line approach can improve the analysis efficiency through high-throughput pretreatment when large batches of samples are encountered, meaning the off-line approach is still an effective model. Ion imprinting technology has been developed based on existing molecular imprinting technology, with four main steps present in the synthesis of ion imprinted polymers. First, ion imprinting technology uses metal ions as templates. Then, these templates are combined with the functional monomers through coordination, electrostatic or hydrogen bonding. The functional monomers simultaneously surround and fix the templates, after which the cross-linkers and functional monomers polymerize to prepare ion-imprinted polymers with a specific structure and composition. Finally, the imprinted holes are created in the polymers by eluting the template ions. Therefore, the template molecules, functional monomers, and cross-linkers are three precursors necessary for synthesizing ion-imprinted polymers. These polymers can specifically bind to the imprinted metal ions with accuracy, sensitivity, and reliability. In recent years, they have been widely used in separating, enriching, analyzing, and detecting elemental species. During solid-phase extraction, the non-magnetic adsorbent materials dispersed in the sample solution need to be separated by centrifugation or filtration, which is time-consuming and laborious. Because an external magnetic field can be used for rapid magnetic solid-phase extraction, it has become a potential method for separating and enriching elemental species. This review systematically summarizes the latest progress in ion-imprinting technology, including its principle and the preparation methods of ion-imprinted polymers. The challenges faced by ion imprinting technology are analyzed in the context of the development of ion-imprinting magnetic solid-phase extraction in elemental speciation analysis. Finally, the direction of future development and the strategies of ion imprinting technology in elemental speciation analysis are proposed. It is important to exploit novel organic-inorganic hybrid polymerization-based multifunctional ion-imprinted magnetic nanocomposites for the magnetic solid-phase extraction and separation of elemental species. By establishing the pretreatment protocols with high recognition selectivity, strong separation ability, large adsorption capacity, and good speciation stability, we expect to achieve the research objectives of simultaneously separating and enriching the multiple-species of typical metal/metalloid elements in environmental and biological samples.

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Determination of four fungicides in water by magnetic solid phase extraction-ultrahigh performance liquid chromatography-tandem mass spectrometry using covalent organic framework material WANG Pan, MA Jiping, LI Shuang, CHENG Jiawen, ZOU Zongyue 2022, 40 (11):  988-997.  DOI: 10.3724/SP.J.1123.2022.08023 Abstract ( 93 )   HTML ( 23 )   PDF (2557KB) ( 64 )   Fungicides can lead to soil and plant diseases after long-term enrichment in the environment; they can also penetrate deeper into the soil and groundwater by rainwater or irrigation, threatening the water environment and human health. Therefore, it is crucial to develop a simple, rapid, efficient, and sensitive analytical method for the detection of fungicides in the water environment. Sample pretreatment is important for the extraction and enrichment of pollutants from environmental water. Magnetic solid phase extraction (MSPE) is a new sample pretreatment method, which uses magnetic materials as adsorbents dispersed in solution, and rapid separation can be achieved by the aid of external magnets. Because of its advantages of short analytical time, less organic solvent consumption, and easy separation of adsorbents, MSPE has attracted much attention. The key to MSPE is the preparation of highly selective magnetic adsorbents. Covalent organic frameworks have the advantages of large surface area, good chemical and thermal stability, tunable porous structure, low density, and easy functionalization, all of which are ideal for adsorbing fungicides. The concentration of fungicides in environmental water is low. Ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has high sensitivity and high selectivity, which is suitable for the analysis of fungicides. In this work, a magnetic covalent organic framework Fe3O4@TpBD was prepared by an in situ method, as the MSPE sorbent material to enrich of benzimidazole fungicides (thiabendazole, carbendazim, fuberidazole) and organic sulfur fungicide (isoprothiolane) in environmental water. An extraction method based on π-π conjugation, hydrogen bonding, and electrostatic interaction between Fe3O4@TpBD and the fungicides, in combination with UHPLC-MS/MS, was developed for the determination of four trace fungicides in water. Transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Fourier transform-infrared spectroscopy (FT-IR) were performed to confirm the successful synthesis of Fe3O4@TpBD and to characterize this material. A series of experiments were carried out to decide the optimal extraction conditions, i. e., the magnetic ratio and dosage of Fe3O4@TpBD, pH of the water sample, adsorption time, type and volume of the eluent, elution time, and salinity. Gradient elution was carried out with methanol-water as the mobile phase. The target analytes were separated on an ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 μm), and multiple reaction monitoring (MRM) was conducted in the positive electrospray ionization mode. The ion source temperature and ion source voltage were set to 500 ℃ and 5 kV, respectively. The analytical method was established under the optimized extraction conditions. The four fungicides showed good linearity in the range of 3-1200 ng/L, with linear correlation coefficients greater than 0.998. The limits of detection (LODs) and limits of quantification (LOQs) of this developed method were 0.06-0.28 ng/L and 0.20-0.92 ng/L, respectively. Recovery tests were performed at three spiked levels of 15, 150, and 600 ng/L, with relative standard deviations of 2.8% to 10.0% (intra-day) and 4.4% to 15.7% (inter-day). The accuracy of the established analytical method was investigated by using it to test real water samples, and satisfactory recoveries for the four analytes were achieved within 77.1% to 119.1%. Trace amounts of carbendazim were detected in the reservoir water at 27.5 ng/L. The method has good sensitivity, accuracy, and precision, and the operation process is convenient.

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Determination of three penicillin residues in milk by solid-phase extraction-ultra performance liquid chromatography-tandem mass spectrometry using a covalent triazine framework sorbent LI Qin, DAI Shuyu, YANG Yuan, FENG Yumin, LIAN Hongzhen, ZHANG Shusheng, ZHANG Wenfen 2022, 40 (11):  998-1004.  DOI: 10.3724/SP.J.1123.2022.07002 Abstract ( 81 )   HTML ( 22 )   PDF (1487KB) ( 49 )   A method based on solid-phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS) was established for the determination of gpenicillin, cloxacillin, ampicillin residues in milk. Using self-made covalent triazine frameworks (CTFs) as the solid-phase extraction sorbents, the main factors influencing the efficiency of the solid-phase extraction columns, such as the sorbent amount, eluent type, eluent volume, and flow rate, were optimized. The extraction and purification conditions for the samples were also investigated. The optimal extraction effect was achieved at a flow rate of 3 mL/min with 60 mg CTFs and 6 mL eluent solution (acetonitrile). Separation was carried out on a Waters ACQUITY UPLC BEH C18 column, and 0.1% formic acid aqueous solution-acetonitrile was used as the mobile phases for gradient elution. The filtrate was detected by ultra performance liquid chromatography-tandem mass spectrometry, identified by electrospray ionization (ESI) in the positive mode using multiple reaction monitoring, and quantified using external standards. The calibration curves of the three penicillins showed good linearity and the correlation coefficients of the linear regression equations for the three target analytes were all greater than 0.999. The limits of detection (LODs) and limits of quantification (LOQs) were 0.05-0.10 μg/kg and 0.1-0.4 μg/kg, respectively. The average recoveries of the three analytes were 84.9%-94.1%, and the relative standard deviations (RSDs, n=5) were 1.66%-3.27%. Moreover, the mechanism of interaction between the CTFs and the target analytes was analyzed. The results revealed the existence of π-π and hydrogen-bond interactions between the CTFs and analytes. The results further indicated that the CTFs could be successfully used for the enrichment and purification of penicillins in milk. The proposed method has the advantages of high precision, good reproducibility, high resolution, and short analysis time, and it is suitable for the qualitative and quantitative determination of trace targets in complex matrices.

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Analysis of parabens in environmental water samples by covalent organic framework-based magnetic solid-phase extraction-high performance liquid chromatography BAO Yue, ZHAI Yixin, NING Tao, CHEN Pin, ZHU Shukui 2022, 40 (11):  1005-1013.  DOI: 10.3724/SP.J.1123.2022.06006 Abstract ( 86 )   HTML ( 21 )   PDF (5393KB) ( 130 )   Parabens are a class of antimicrobial preservatives that are widely used in cosmetics, pharmaceuticals, and food products because of their ease of production, antimicrobial effect, and low price. The widespread use of these parabens, poses potential risks to human health. Therefore, it is necessary to establish a simple and rapid method for the detection of parabens. The large number of substrate interferences in complex samples is an important factor affecting the sensitivity of analytical methods. Magnetic solid-phase extraction (MSPE) has received much attention because of its advantages of easy operation, short extraction time, small sample amount, low cost, and environmental friendliness. Covalent organic frameworks (COFs) with high crystallinity, high specific surface area, adjustable pore size, regular porosity, as well as high chemical and thermal stability are now widely used in separation and analysis. Therefore, a sample pretreatment method combining MSPE and COF for the analysis of parabens in complex matrices is very promising. A magnetic covalent organic framework, Fe3O4@TbBd, was successfully synthesized by the Schiff base reaction of 1,3,5-triformylbenzene (Tb) and benzidine (Bd) at room temperature using Fe3O4 nanoparticles as magnetic cores. Characterization by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) measurements, etc. revealed that the magnetic COF has high magnetic responsiveness, as well as good thermal and chemical stability, which make it an ideal adsorbent for the MSPE of parabens. Some factors related to the extraction efficiency, including the amount of adsorbent, extraction time, pH, desorption solvent, desorption time, and number of desorption were systematically investigated. A method involving MSPE and high performance liquid chromatography-ultraviolet detection (HPLC-UV) based on the Fe3O4@TbBd was developed for the determination of four parabens (ethylparaben, propylparaben, butylparaben, and benzylparaben) in environmental water samples. Under the optimal extraction conditions, the method showed good linearities. The limits of detection and limits of quantification were 0.2-0.4 μg/L and 0.7-1.4 μg/L for the four analytes, respectively. The recoveries at three spiked levels were in the range of 86.1%-110.8% with intra-day and inter-day RSDs of less than 5.5% and 4.9%, respectively. The method was successfully applied to the determination of parabens in East Lake water, Yangtze water, and domestic wastewater. Ethyl paraben and propyl paraben were detected in domestic wastewater at the levels of 1.8 μg/L and 0.4 μg/L, respectively. The recoveries of the parabens at different spiked levels ranged from 80.7% to 117.5%, with RSDs of 0.2%-8.8%. The method has good potential for the determination of parabens in environmental water samples because of its operational simplicity, short extraction time, high sensitivity, and environmental friendliness.

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Detection of four biogenic amines by liquid chromatography based on aptamer signal replacement combined with cyclic amplification SONG Chang, LIU Chang, MA Ziyu, PAN Ruirong, SHI Haiwei, KONG Dezhao, ZHANG Jinghui, SHEN Wei, TANG Sheng 2022, 40 (11):  1014-1021.  DOI: 10.3724/SP.J.1123.2022.07004 Abstract ( 90 )   HTML ( 14 )   PDF (1986KB) ( 43 )   Supporting Information Biogenic amines (BAs) represent a class of potentially harmful substances in foods and medicines. Their content is thus an important indicator of proper hygiene in food preparation, and purity of medicines. It is of great practical significance to establish accurate and sensitive detection of BAs in food and drugs. In this study, a high performance liquid chromatography (HPLC) method was developed for the simultaneous detection of multiple BAs in fish, pork and antibiotics based on aptamer signal replacement and cyclic amplification strategy. First, non-fluorescent targets were converted into fluorescent nucleic acid probes using a two-step replacement process. Subsequently, a large number of nucleic acid probes with different lengths and base sequences were generated using a double-stranded specific nuclease-assisted signal amplification strategy. Finally, various BAs in real samples were accurately identified using an HPLC platform. The influence of base sequence and nucleic acid probe length on separation via HPLC was studied to improve discrimination among fluorescent signals. Four different sequences were selected as tails to the DNA probe, and their retention times increased in turn. Experimental conditions, including column temperature, flow rate, gradient elution process, reaction temperature, and incubation time, were optimized by orthogonal experiments to further improve signal separation efficiency. Specifically, the methanol gradient was changed from 10% to 20% during 0-20 min, 35 ℃ of column temperature and 1.0 mL/min of flow rate were chosen as the HPLC conditions. The final resolution of chromatographic peaks was 3.44, 3.59 and 2.37, indicating complete separation between peaks. Optimal incubation time for BA capture by aptamer was 120 min, and optimal dosage of duplex specific nuclease (DSN) and Mg2+were 0.9 U and 30 mmol/L. The optimal pH, incubation temperature, and DSN incubation time were 7.0, 40 ℃ and 210 min, respectively. The proposed method exhibited high sensitivity towards BAs, with a linear range of 1 pmol/L-1 μmol/L, and the limits of detection of tyramine, histamine, spermine, and tryptamine were 0.25, 0.21, 0.27 and 0.19 pmol/L, respectively. The feasibility of this method was verified, and contrast experiments indicated that it could achieve highly selective detection of four BAs in one run. The applicability of this integrated method was also investigated for the detection of real samples (gentamycin sulfate, fish and pork). To assess the matrix effect, each BA with different concentrations were spiked into real fish and pork samples. Relative recoveries and relative standard deviations (RSDs) ranged from 101.2% to 104.5% and from 1.5% to 4.3%, respectively. The above detection results for real samples showed that this method could accurately capture, separate, and identify BAs in complex matrix samples. This strategy can effectively improve analyte selectivity and reduce the matrix effect. This assay is thus expected to provide a new approach for food and drug analyses.

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Hollow bimetal-organic framework material as solid-phase microextraction fiber coating for highly sensitive detection of polycyclic aromatic hydrocarbons ZHANG Wenmin, LI Qingqing, FANG Min, ZHANG Lan 2022, 40 (11):  1022-1030.  DOI: 10.3724/SP.J.1123.2022.05001 Abstract ( 77 )   HTML ( 17 )   PDF (2585KB) ( 36 )   Polycyclic aromatic hydrocarbons (PAHs) are among the most harmful persistent organic pollutants that possess high carcinogenicity and teratogenicity; hence, establishing a highly sensitive analytical method for monitoring PAHs in environmental samples is an urgent need. However, due to the low PAHs content in environmental samples and the complex matrix of the samples, it is difficult to directly determine the amount of PAHs using the existing analytical instruments. Therefore, an essential pretreatment of environmental samples should be carried out before instrumental analysis. In most pretreatment techniques, the extraction efficiency depends on the characteristics of the extraction materials. Currently, metal-organic framework materials (MOFs), which are porous materials self-assembled by metal ions and organic ligands, are used as solid-phase microextraction (SPME) coating materials for the extraction of PAHs. However, the following problems limit the application of MOFs in the SPME field: (1) MOF coating materials often require a long equilibration time for extraction because the it is difficult for the target to reach the deep adsorption sites; (2) In addition, most MOFs are formed by the coordination of single metal ions with organic monomers. The single type of open metal active sites is not conducive for realizing high extraction performance. In this study, a hollow bimetal-organic framework (H-BiMOF) was synthesized by the solvothermal method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption-desorption analysis, thermogravimetric analysis, etc. The TEM images and XRD patterns demonstrated the successful synthesis of H-BiMOF with a hollow structure, which was formed through the competitive coordination between benzoic acid and water. The H-BiMOF material showed type-Ⅳ isotherms with a surface area of 1437 m2/g and excellent thermal stability. Subsequently, a H-BiMOF-coated SPME fiber was prepared by the physical adhesion method and used to extract trace PAHs from environmental samples. Due to the hollow structure of H-BiMOF, the prepared fibers offer the advantages of high utilization of specific surface area as well as short mass transfer distance, so that the extraction process quickly reaches equilibrium. At the same time, the introduction of bimetals provides a variety of metal active sites, which improves the extraction efficiency of the fiber against electron-rich cloud targets such as PAHs. The prepared fiber also had good service life, with at least 150 cycles. Combined with gas chromatography-tandem mass spectrometry (GC-MS/MS), a new method for the determination of PAHs in environmental water samples was established. Single factor experiments were performed to investigate the effects of the SPME conditions on the analytical performance. Under the optimal conditions, the established method showed low limits of detection (0.01-0.08 ng/L), wide linear range (0.03-500.0 ng/L), good linearity (correlation coefficients≥0.9986), and acceptable reproducibility (relative standard deviations≤9.8%, n=5). Finally, typical water samples were analyzed by the established method. Four environmental water samples were collected from Dianchi Lake, Poyang Lake, Taihu Lake, and Xihu Lake in China. No benzo(a)anthracene (BaA) and chrysene (CHR) were detected in any of the water samples. However, 17.9 ng/L of fluorene (FLU) and 5.3 ng/L of phenanthrene (PHE) were found in the Poyang Lake sample; 11.3 ng/L of fluoranthene (FLA) and 24.2 ng/L of pyrene (PYR) were found in the Taihu Lake sample; 50.0 ng/L of FLU, 19.5 ng/L of PHE, 14.9 ng/L of anthracene (ANT), 34.2 ng/L of FLA, and 44.5 ng/L of PYR were found in the Xihu Lake sample. The contents of the PAHs detected in all the lake water samples were lower than the Chinese National Standard GB 5749-2006 (2000.0 ng/L). The results of this study indicate that the developed method is suitable for the sensitive detection of trace levels of PAHs in real environmental water samples.

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Solid phase microextraction of benzenes in river water by pomelo peel biochar CHEN Jingjing, ZHANG Zhuoran, YU Jianfeng, TANG Shiming, CUI Bingwen, ZENG Jingbin 2022, 40 (11):  1031-1038.  DOI: 10.3724/SP.J.1123.2022.02006 Abstract ( 73 )   HTML ( 16 )   PDF (3569KB) ( 60 )   Pomelo peel, as a by-product of pomelo consumption, is rich in various fiber and functional compounds. The utilization of the valuable components found in pomelo peel may mitigate environmental concerns. In this study, pomelo peel rich in lignin and oxygen-containing functional groups was used to prepare pomelo peel biochar (PPB) via temperature-programmed pyrolysis at different temperatures (800 ℃ and 1000 ℃). Their structures were investigated by N2 adsorption-desorption isotherms and BJH pore size distribution. The results showed that PPB1000 (pomelo peel biochar prepared at 1000 ℃) had a higher specific surface area (749.9 m2/g), larger pore volume (0.42 cm3/g), more concentrated pore size distribution (2-3 nm), and better adsorption performance than commercial activated carbon. PPB1000 exhibited excellent capability to capture benzenes (BTEX, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X)) through hydrogen bonds, π-π, and electrostatic interactions. Additionally, their honeycomb porous structure could provide additional adsorption sites and material transport paths. PPB1000 was coated on iron wire using the sol-gel method to prepare chemically and mechanically stable solid phase microextraction (SPME) fibers. By combining PPB1000-based SPME analysis with gas chromatography-flame ionization detection (GC-FID), an effective method was developed for the extraction and determination of BTEX. The optimized method had low LODs (0.004-0.032 μg/L), wide linear range (1-100 μg/L), and good linear relationship (determination coefficients, r2≥0.9919). The RSDs of the intra-batch (n=6) and inter-batch (n=5) precisions were 1.04%-6.56% and 1.03%-12.42%, respectively. The method validation results showed that PPB1000 had good stability. Compared with the commercial reagent polydimethylsiloxane (7 μm), PPB1000 had a higher extraction efficiency. When applied to the analysis of BTEX in natural water samples, trace levels of ethylbenzene (4.80 μg/L), o-xylene (3. 00 μg/L), and m-xylene and p-xylene (2.46 μg/L) were detected. Recovery tests were performed to validate the reliability of the method, and recoveries were between 75.7% and 117.6%. This effective pretreatment process combined with GC-FID could realize the rapid detection of BTEX and is promising for the analysis of BTEX in complex matrixes in the future.

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Surface-enhanced Raman detection of deoxynivalenol allenol in agricultural products CHEN Mingming, SU Bihang, HUANG Jianli, FU Fengfu, DONG Yongqiang 2022, 40 (11):  1039-1046.  DOI: 10.3724/SP.J.1123.2022.06021 Abstract ( 58 )   HTML ( 15 )   PDF (4444KB) ( 35 )   Fungal toxins are secondary metabolites of fungi. Food is highly susceptible to contamination by various fungal species that produce fungal toxins during production and storage. Fungal toxins can cause either acute or chronic poisoning from long-term, low-dose ingestion. Therefore, fungal toxins have become a topic of international interest as a food safety issue. Deoxynivalenol (DON) is a single-terminal sporam toxin produced predominantly by Fusarium graminae and Fusarium pinkosa. DON is globally one of the most common fungal toxins contaminating grain, food, and feed. Various methods have been applied for screening and detecting DON; however, these methods utilize expensive instruments and entail complex operations, poor repeatability, and low sensitivity. Therefore, the development of a simpler, more rapid, and sensitive sensing technology for DON detection is important for applications within the agriculture and food industry. Recently, surface-enhanced Raman scattering (SERS) has become a rapidly developing spectral analysis technology with unique advantages, including high sensitivity, high throughput, and rapid response rates. Therefore, attempts have been made to apply the SERS technique to detecting DON. However, due to the limitations concerning SERS substrates, the currently established SERS method exhibits serious problems, including low sensitivity and weak anti-interference ability, and cannot meet the requirements of sample detection. Recently, our group has prepared aggregated silver nanoparticles (a-AgNPs/CDs) with high SERS activity by using single-layer carbon-based dots (CDs) as a capping agent. Moreover, the obtained materials (a-AgNPs/CDs) were combined with hydrogel technology to prepare novel hydrogel SERS chips. The obtained SERS chips exhibited several advantages over traditional SERS substrates, such as high sensitivity, long-term stability, improved uniformity, and strong anti-interference capabilities. Herein, a novel SERS method for rapid screening and detection of DON in grains was established using a portable Raman spectrometer based on the developed hydrogel SERS chips. The main experimental conditions were optimized before the SERS detection of DON; this included the optimization of the hydrogel SERS chip soaking temperature and time in the DON solution. It was found that the optimal soaking temperature and time were 40 ℃ and 5 min, respectively. Under the optimal SERS detection conditions, the linear response range of DON was 1-10000 μg/kg (correlation coefficient (R2)=0.9967), and the limit of detection (LOD) was 0.14 μg/kg. Due to the unique pore size structure of the hydrogel, common sugar, protein, oil, pigment, and other interfering substances in the sample matrix were blocked outside the hydrogel. Therefore, only simple extraction was required while detecting complex samples. This method was applied to detecting DON in wheat flour, yielding recoveries of 97.3%-103% with relative standard deviations of 4.2%-5.0%. The established SERS method for DON detection exhibits a broader response range, high sensitivity, good repeatability, rapid response, simple operation, and strong anti-interference capability. This shows that the laboratory-constructed hydrogel SERS chip has excellent potential for rapid screening and detection of biotoxins in food.