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Chinese Journal of Chromatography
2021, Vol. 39, No. 2
Online: 08 February 2021

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Advances in technologies for large-scale enrichment and identification of ribonucleic acid-protein complexes FAN Zhiya, QIN Weijie 2021, 39 (2):  105-111.  DOI: 10.3724/SP.J.1123.2020.07019 Abstract ( 239 )   HTML ( 147 )   PDF (1876KB) ( 126 )   Ribonucleic acid (RNA) rarely exists alone in the cell. RNAs interact with a variety of proteins and form RNA-protein complexes (RP-complexes) in every step of their life cycle, from transcription to degradation. These RP-complexes play key roles in regulating a variety of physiological processes. Defects in the composition and function of RP-complexes have been associated with many diseases, including metabolic disorders, muscular atrophy, autoimmune diseases, and cancer. It is hence evident that deciphering the highly complex interaction network of RNA-binding proteins (RBPs) and their RNA targets will provide a better understanding of disease development and lead to the discovery of new targets for cancer therapy. Large-scale identification of RP-complexes at the omics level is a prerequisite for obtaining insights into the complex RNA-protein interaction network. As the first step in omics-wide decoding of RP-complexes, enrichment and purification of RP-complexes is a highly challenging task. Recently, intensive efforts have been undertaken to better enrich and identify RP-complexes. Generally, the enrichment strategies can be classified into two major categories: in vitro and in vivo. Although it has been successfully applied in many studies, the in vitro transcribed bait RNA lacks modifications or structural similarity compared with its natural counterpart. Further, since the proteins relocate and remodel after cell lysis, the use of cell lysates as a protein source may result in capturing false interacting proteins that bind non-physiologically with the bait RNA. Finally, weak interactions between the non-covalently bound proteins and RNA require mild washing to remove non-specific binding, which needs careful optimization. However, substantial sample loss is inevitable. To overcome the disadvantages of in vitro approaches, in vivo cross-linking strategies that “freeze” natural RNA-protein complexes in intact cells via covalent cross-linking have become increasingly popular. The in vivo methods allow RNA to interact with proteins in the intracellular environment. Therefore, the RP-complexes formed under physiological conditions are more biologically relevant than those obtained by in vitro methods. We herein summarize recent in vivo methodological advances in the large-scale enrichment and identification of RP-complexes, including cross-linking and immunoprecipitation (CLIP) and related methods, click chemistry-assisted methods, and organic phase separations. CLIP involves irradiating living cells with 254-nm ultraviolet (UV) light to establish covalent bonds between RNA and proteins. This enables CLIP to purify RNAs bound to a specific RBP under conditions that are stringent enough to prevent co-purification of nonspecifically bound proteins or free RNAs. Since the original study, multiple variant protocols have been derived to increase both efficiency and convenience. Photoactivatable ribonucleoside-enhanced-CLIP (PAR-CLIP) introduces a variation in the crosslinking strategy. Cells were preincubated with photoactivatable ribonucleosides 4-thiouridine (4SU) or 6-thioguanosine (6SG), which enables protein-RNA crosslinking with 365-nm UV-A irradiation. It increases the efficiency of cross-linking between RNA and RBPs and is particularly valuable for studying the interactions between RBPs and nascent RNA. Using a click chemistry-assisted strategy, an alkyne modified uridine analog, 5-ethynyluridine (EU), was incorporated into nascent RNAs via metabolic incorporation in living cells. Combined with UV irradiation-based cross-linking, the alkyne-functionalized RNA and the bound proteins were purified in a poly A-independent fashion by the highly selective bioorthogonal copper (I)-catalyzed azide-alkyne cycloaddition using azide-modified beads. Thus, full lists of both coding and non-coding RNAs with their interacting proteins can be purified, which is a major methodological advance. Organic phase separation methods exploiting the physicochemical difference between cross-linked RP-complexes and free RNA and proteins do not require metabolic-based alkyne labeling or polyA-based RNA capture. Each method has unique strengths and drawbacks, which makes it important to select optimal approaches for the biological question being addressed. We hope that this review points out the current limitations and provides future directions to facilitate further development of methods for large-scale investigation of RP-complexes.

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Advances in high-throughput proteomic analysis WU Qiong, SUI Xintong, TIAN Ruijun 2021, 39 (2):  112-117.  DOI: 10.3724/SP.J.1123.2020.08023 Abstract ( 686 )   HTML ( 62 )   PDF (1060KB) ( 328 )   Proteomic analysis aims at characterizing proteins on a large scale, including their relative abundance, post-translational modifications, protein-protein interactions and so on. Proteomic profiling helps to elucidate the mechanisms of disease occurrence and to discover new diagnostic markers and therapeutic targets. Mass spectrometry (MS)-based proteomic technologies have advanced to allow comprehensive qualitative and quantitative proteome profiling across a myriad proteins in cells and tissues. High-throughput proteomics is the core technique for large-scale protein characterization. With the increased demand for large cohort proteomic analysis in the biomedical research field, high-throughput proteomic analysis has become a critical issue that needs to be urgently addressed. The standard shotgun proteomic workflow comprises four steps, including sample preparation, peptide separation, MS acquisition, and data analysis. Advances in these four steps have contributed to the development of high-throughput proteomics. In this review, we aimed at summarizing the current information on the state-of-the-art development of high-throughput proteomic analysis, mainly including the following topics: (1) High-throughput, automatic proteomic sample preparation methods based on liquid-handling workstations. The automation of the proteomic sample preparation steps is essential for high-throughput proteomic analysis, which will significantly reduce variation of manual operation and sample loss by multistep sample processing. The commercial liquid handling workstations, including King FisherTM Flex, Agilent Bravo, AssayMAP Bravo, and Biomek® NXP, perform the handling steps of 96- or 384-channel microplate formats using a mechanical arm that increases the throughput and robustness of sample preparation. (2) High-throughput proteomic detection methods based on microliter-flow-rate liquid chromatography coupled with mass spectrometry (micro-flow LC-MS/MS). Nanoliter-flow-rate liquid chromatography coupled with mass spectrometry (Nano-flow LC-MS/MS) is widely used in classic proteomic research due to its excellent sensitivity, which often comes at the expense of robustness. Owing to the improved robustness and decreased injection-to-injection overheads, micro-flow LC-MS/MS has become increasingly popular in high-throughput proteomic analysis. (3) Using MS instrumentation with high sensitivity and fast scanning speed to realize in-depth proteomic analysis coupled with short chromatographic gradient separation. In recent years, new MS instrumentation continues to exhibit speed of analysis and sensitivity enables the large-scale profiling of hundreds of samples. In particular, ion mobility-based MS, such as timsTOF Pro and Exploris 480 equipped with a front-end high field asymmetric waveform ion mobility spectrometry (FAIMS), which provides fast, sensitive, and robust proteome profiling, thus shifting proteomics to the high-throughput era. (4) Artificial intelligence-, deep neural network-, and machine learning-based proteome data analysis methods. These approaches have improved comprehensive proteomic analysis efficiency. Specifically, the emergence of new algorithms and the up gradation of search engines accelerate the process of high-throughput data analysis. Additionally, the challenges and future development of high-throughput proteomics are prospected. In conclusion, high-throughput proteomic technologies are expected to gradually “transform” and become powerful tools for large cohort proteomic analysis in the near future.

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Reactive oxygen species stimuli-responsive nanocarriers ZHOU Wen, YANG Kaiguang, ZHAO Baofeng, ZHANG Lihua, ZHANG Yukui 2021, 39 (2):  118-124.  DOI: 10.3724/SP.J.1123.2020.11014 Abstract ( 265 )   HTML ( 33 )   PDF (1040KB) ( 119 )   Nanocarriers are nanoscale delivery systems composed of natural or synthetic polymers, which are advantageous in reducing drug toxicity while improving drug targeting and utilization. With the advancement of biomedical technology, it is revealed that reactive oxygen species (ROS), a class of oxidative metabolites, show abnormal overexpression in disease-related parts of the body. Hence, ROS stimuli-responsive nanocarriers have gained increasing attention, and recent developments are expected to realize controllable drug release. Based on linkers with different ROS-responsive mechanisms, a series of ROS-responsive nanocarriers have been designed to achieve specific controlled drug release under the stimulation of the ROS at the disease site. This article mainly focuses on ROS-responsive linkers, which have been commonly used for the synthesis of nanocarriers in recent years. Accordingly, the linkers are classified as chalcogen-containing responsive linkers (thioether, thioketal, selenide, diselenide, and telluride) and responsive linkers containing other elements (arylboronic ester, ferrocene, and peroxalate ester). ROS stimuli-responsive nanocarriers are fabricated by introducing ROS-responsive linkers in different design principles. Owing to the ROS-responsive linkers, the nanocarriers follow different responsive mechanisms, including hydrophobic-to-hydrophilic phase transition and cleavage. This article discusses the degree of responsiveness of nanocarri-ers and the specific release of drugs from nanocarriers upon ROS-stimuli, as well as their applications in vivo. In particular, on the basis of intelligent drug release and precision medicine, this article also emphasizes the importance of the biocompatibility and biodegradability of nanocarriers.

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Advances in construction of triazine-based porous organic polymers and their applications in solid phase microextraction WANG Zhuo, WANG Wenjin, ZHANG Shuaihua, WANG Chun, WANG Zhi 2021, 39 (2):  125-129.  DOI: 10.3724/SP.J.1123.2020.07036 Abstract ( 143 )   HTML ( 25 )   PDF (945KB) ( 185 )   The large surface area, adjustable pore structure, good thermal and chemical stabilities, and abundant π-electron systems make triazine-based porous organic polymers (TPOPs) as promising porous materials for gas storage, catalysis, energy conversion and adsorption. Recently, TPOPs have aroused ever-increasing interest and are considered as one of the research highlights in solid phase microextraction (SPME) and other sample pretreatment techniques. This minireview summarizes the recent advancements in the synthesis of TPOPs and their applications in SPME. The application prospects of the TPOPs in SPME and other sample pretreatment techniques are also presented.

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Advances of electrodialytic technologies used in ion chromatography YANG Bingcheng, LI Zongying 2021, 39 (2):  130-133.  DOI: 10.3724/SP.J.1123.2020.07016 Abstract ( 145 )   HTML ( 31 )   PDF (991KB) ( 110 )   An electrodialysis device is used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric potential. They can produce hydronium or hydroxide ions via electrodialysis water, which can be used for online preparation of eluents or suppression or detection in ion chromatography (IC). As opposed to the manual preparation of eluents or regenerant solutions, electrodialysis devices have the advantages such as green, efficient and high purity. Thus, IC systems equipped with electrodialysis devices dominate the majority uses of IC system, and more importantly, find widespread application. The present thesis briefly summarizes the latest developments in this area.

Reviews

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Recent advances in applications of fragment/dummy molecularly imprinted polymers WANG Yixiao, LI Jinhua, WANG Liyan, QI Ji, CHEN Lingxin 2021, 39 (2):  134-141.  DOI: 10.3724/SP.J.1123.2020.08008 Abstract ( 233 )   HTML ( 44 )   PDF (1987KB) ( 94 )   Molecularly imprinted polymers (MIPs) are designed to mimic the specific binding principle of enzymes to substrates or antigens to antibodies, while holding several advantages such as structure predictability, recognition specificity, easy preparation, low cost, high physical robustness, and thermal stability. Therefore, they have been widely applied in many fields including sample preparation (pretreatment), sensing analysis (chemo/biosensors), biomedicine, and environment/food analysis. To date, several strategies were developed for MIPs preparation, aiming to simplify the preparation process and/or improve the properties of the polymers, greatly broadening its usability. The exploration in various advanced imprinting strategies and their combinational use has become a research hotspot in MIPs preparation, among which the fragment imprinting strategy and the dummy template imprinting strategy are especially favored. Fragment imprinting, also called segment imprinting, uses a partial structure of the target molecule as a pseudo-template to prepare MIPs. This strategy is useful to target molecules that are not easy to obtain or that are too large to be used as templates, providing a feasible method for imprinting target analytes that are easy to inactivate or infect, as well as macromolecules that are difficult to imprint. In turn, dummy template imprinting uses molecules with structure, shape, and size similar to the target analytes as templates for imprinting. Because the target is not directly used as a template, this strategy can overcome problems of template leakage, as well as solve target molecule-related difficulties as they can be expensive, infectious, flammable, explosive, or chemically instable. This mini-review compiles information of several articles published in the last four years across ACS, Elsevier, RSC, and other databases, summarizing the most recent advances in the application of fragment/dummy template MIPs (FMIPs/DMIPs). Herein, the biomedical application of FMIPs is mainly addressed as a strategy for the detection of proteins and microorganisms, and the application of FMIPs in the field of food analysis is also explored. In recent years, the imprinting of mammalian cells has made some progress in the application of FMIPs. Mammalian cells, especially cancer cells, overexpress some proteins and sugars, which are good fragment templates. Consequently, the fragment imprinting strategy is widely used in cancer cell imaging, localization, and treatment. Moreover, due to the complicated structure and easy inactivation of some proteins, their MIPs are often prepared by fragment imprinting (also called epitope imprinting). As some microorganisms are infectious, imprinting microorganisms directly can pose a risk; therefore it is safer to also use the fragment imprinting strategy in such cases. The recent application of fragment imprinting strategy in other areas remains scarce. Nonetheless, three studies in the food analysis have explored this possibility. DMIPs are widely used in sample pretreatment and sensing analysis, and they are mainly used as SPE adsorbents for packed SPE, dispersive SPE (DSPE), magnetic SPE (MSPE), and matrix solid phase dispersion (MSPD) extraction. In addition, DMIPs are employed as molecularly imprinted membrane materials. As a result, by virtue of DMIPs, selective extraction and enrichment of target analytes from complicated samples can be achieved. MIP-based sensors can either recognize or transduce, meaning that they can specifically recognize and bind target analytes as well as generate output signals for detection. Because of the high selectivity of MIPs, the use of a dummy template imprinting strategy solves the problem of template leakage in the process of recognition and adsorption, further improving the detection accuracy and sensitivity of the sensor. These features expand the application range of MIP-based sensors. This review briefly overviews the construction and application of chemiluminescence and fluorescence sensors based on DMIPs. Lastly, the advantages and disadvantages, differences, and relationships among the two strategies are summarized. Despite of their potential, four main challenges still remain as major setbacks for the application of FMIPs and DMIPs: (i) the difficulty to select or prepare appropriate fragment templates and dummy templates; (ii) how to ensure that there is almost no difference in the recognition adsorption selectivity between the fragment/dummy template and the original template, so as to ensure optimal recognition specificity; (iii) the use of, environment-friendly reagents to reduce pollution during FMIPs/DMIPs preparation and use to conform with green chemistry requirements; (iv) how to strengthen the industrial and commercial applications of FMIPs and DMIPs. Therefore, significant efforts should be made to develop new imprinting strategies and techniques, as well as to adopt combinational imprinting approaches for FMIPs/DMIPs preparation to expedite the sustainable development and efficient application of FMIPs and DMIPs.

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Methods and applications of single-cell proteomics analysis based on mass spectrometry QIN Shaojie, BAI Yu, LIU Huwei 2021, 39 (2):  142-151.  DOI: 10.3724/SP.J.1123.2020.08030 Abstract ( 470 )   HTML ( 57 )   PDF (2743KB) ( 429 )   The cell is the smallest unit of living organisms. Although cells often assemble to serve a common function, intercellular heterogeneity often exists due to different genetic and environmental effects. Therefore, single-cell analysis has been regarded as an indispensable means to investigate cell heterogeneity, especially when researching cell differentiation, disease diagnosis, and therapy. As the chief factors influencing cell and biological activities, proteins have long been a major concern in biochemistry. However, due to their intrinsic lack of amplification characteristics, wide species variety, low abundance, and wide dynamic range, proteins are scarcely studied in single-cell research when compared with other biological macromolecules. Therefore, ultra-sensitive single-cell proteomics analysis methods are urgently required. Among all general measurement techniques, fluorescence methods possess high sensitivity and a capability of dynamic tracing, but low target numbers impose restrictions on their broad application in real “proteomic” studies. Similarly, electrochemical methods adapt to electrochemically active molecules, which miss the majority of proteins. Mass spectrometry (MS), as the core approach of proteomic studies, provides high-sensitivity and high-throughput analysis of proteins together with abundant structural information, which is unique in all the analytical instruments and has made great progress in single-cell proteomic research. Herein, the representative research methods for single-cell proteomics based on MS are reviewed. According to the different protein separation methods used prior to MS analysis, they are divided into three categories, including capillary electrophoresis (CE), liquid chromatography (LC), and direct infusion without the need for separation. First, CE has been widely used in the separation and analysis of complex biological samples owing to its low cost, high analysis speed, and high separation efficiency. Its unique feature is the extraction and transfer of contents from cellular or subcellular regions using capillaries smaller than a single cell size. This sampling method also offers less substrate interference and negligible oxidative damage to the cells. Nonetheless, single-cell analysis based on CE-MS mainly focuses on proteomic studies of large cells because of the considerable sample loss, interface instability, and reproducibility issues. Compared with CE, LC, especially nanoLC, is more widely used in single-cell proteomic research, which mainly depends on its good reproducibility, nanoliter injection volume, low flow rate, low sample loss, and good compatibility with mass spectrometry. In recent years, it has been increasingly applied in the study of large-volume embryos, germ cells, and even somatic cells. More than 1000 proteins have been identified in single HeLa cells using this state-of-the-art single-cell proteomics method. It is worth noting that the single-cell sampling volume based on LC gradually reduces to the nanoliter level, and that the sample loss can be reduced by integrating a series of proteomic sampling processes into small volumes, setting sealing conditions, and reducing washing steps. However, the adequacy of cell lysis, the completeness and efficiency of protein pretreatment, and the labeling of peptide segments are important factors affecting the number and types of protein identification. Compared with protein separation using CE or LC prior to MS analysis, the direct MS analysis, assisted by labelling and signal transformation, eliminates complicated sample pretreatment and simplifies the operation by reducing enzymatic hydrolysis and separation. It also renders higher resolution as well as multi-omics compatibility. So far, the number of proteins detected using this method is limited due to the complexity of the samples. In conclusion, the aspects of throughput, sensitivity, identified protein species, and applications are summarized for each method mentioned above, and the prospect of single-cell proteomic research based on MS in the future is also discussed.

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Progress in the application of deep eutectic solvents to extraction and separation technology ZHAO Zexin, JI Yinghe, LIU Xiaomei, ZHAO Longshan 2021, 39 (2):  152-161.  DOI: 10.3724/SP.J.1123.2020.07015 Abstract ( 705 )   HTML ( 36 )   PDF (1241KB) ( 241 )   With the rapid development of green chemistry, the design and application of the related methods and requisite solvents have received increasing attention in recent years. Deep eutectic solvents (DESs) are mixtures formed from a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD). Generally, ionic liquids (ILs) and DESs have similar physical and chemical properties, and hence, find application in the same fields. However, DESs have many advantages over ILs, such as non-toxicity, environmental friendliness, low cost, and biodegradability. Thus, there are many areas where DESs play a key role and act as new, efficient green extraction solvents. DESs can aid the extraction and separation of different target compounds from a variety of samples, thus promoting the rapid development of sample pretreatment technology. As extraction solvents, DESs offer unique advantages. In dispersive liquid-liquid microextraction (DLLME), DESs show incredible ability to extract residual drugs, metal ions, and bioactive components from complex matrices, which would require complicated sample preparation steps when using traditional organic extraction solvents. Compared with traditional organic extraction solvents, DESs have considerable merits of greenness, hypotoxicity, higher extraction efficiency, etc. Moreover, as a dispersant, a DES can accelerate the diffusion of the extractant in the sample solution during DLLME, owing to its benefits of miniaturization and low cost. Traditional dispersants such as methanol and acetonitrile have many disadvantages, including high volatility, flammability, and toxicity, while DESs are environmentally friendly. Therefore, the combination of DES and DLLME has recently gained prominence in the field of sample preparation. Additionally, the combination of DES and solid-phase extraction (SPE) has broad application prospects. By virtue of their diverse functions, DESs have been used as eluents, in combination with a solid-phase extraction column and a stir bar, to elute analytes from the sorbent surface. The molar ratio of the HBA and HBD is one of the important factors influencing the elution efficiency. DESs can be combined with magnetic multiwalled carbon nanotubes, magnetic graphene oxide, and other nanocomposites to specifically adsorb target analytes through hydrogen bonding, π-π forces, and electrostatic forces. In addition, the DES can be used in the synthesis of magnetic nanocomposites and molecularly imprinted polymers when combined with magnetic materials. Magnetic nanocomposites functionalized with DES show excellent performance and high efficiency in the extraction process. The combination of DES and magnetic materials would promote the development of magnetic materials for green chemistry and expand the application of DES to several other fields. However, to the best of our knowledge, research on the microstructure, physical and chemical properties, and extraction mechanism of DESs is still in its nascent stage. Therefore, exploring the theoretical mechanism and applications of new DESs with special functions would be an essential future research direction. This article integrates the research progress of DESs in extraction separation technology; introduces the preparation, properties, and classification of DESs; and summarizes the applications of DESs in DLLME and SPE.

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Synthesis and application progress of covalent organic polymers in sample preparation for food safety analysis WANG Pingli, CHEN Yanlong, HU Yuling, LI Gongke 2021, 39 (2):  162-172.  DOI: 10.3724/SP.J.1123.2020.08013 Abstract ( 142 )   HTML ( 25 )   PDF (1829KB) ( 240 )   Food safety is closely related to human health and life. Contaminated foods may result in illness or poisoning. For example, perfluorinated compounds can concentrate in the human body, or they can be transferred to the baby during breastfeeding, thus leading to serious health risks. Phthalate esters may cause damage to the liver, lungs, and kidneys. Therefore, food safety has become a hot topic at a global level. Poisonous and harmful substances in foods are derived from the environment, planting or breeding, food contacting materials, and food processing, or due to unsuitable storage conditions. Residues of pesticides and veterinary drugs, organic pollutants, additives, heavy metals, and biotoxins often hamper food safety, causing diseases or even death. The diversity of available food species, complexity of the sample matrix, and lack of information about the source of pollutants render the direct determination of food contaminants difficult. Pretreatment is vital for the accurate analysis of trace toxins in foods. Optimal pretreatment can not only improve the extract efficiency and determination sensitivity, but also prevent instrument contamination. Pretreatment techniques have played an important role in trace determination for complex matrices. Pretreatment methods can be classified as solvent-based and adsorption-based methods. Adsorption-based techniques such as solid-phase extraction, magnetic solid-phase extraction, and solid-phase microextraction are simple and efficient, and hence, are widely used. In these pretreatment techniques, adsorbents play a key role in the extraction effect. In the last few years, metal organic frameworks, metal oxide materials, carbon nanotubes, graphene, and magnetic nanoparticles, as well as a combination of these materials, have been used as adsorbents. These materials are porous and have a large surface area; they are used to enrich trace targets and eliminate interferents. Covalent organic polymers (COPs) are a class of organic porous materials constructed from organic monomers via covalent bonding. Given their excellent characteristics such as light density, good stability, high surface area, structural controllability, and ease of modification, COPs are potential adsorbents. COPs are often synthesized by solvent thermal methods. However, these methods are time-consuming and require toxic solvents and harsh reaction conditions. As alternatives, room-temperature methods, mechanical chemical methods, microwave-assisted methods, and UV-assisted methods have been developed. This has facilitated the synthesis of a wide range of COPs. In this article, the recent applications of COPs in sample pretreatment for food safety analysis are reviewed. COPs can be used in solid-phase extraction by simple packing into columns, polymerization, or chemical bonding in the capillary. Magnetic compounds have been prepared by one-pot synthesis, in situ growth, in situ reduction, or coprecipitation methods and used in magnetic solid-phase extraction. Coatings of solid-phase microextraction fibers are fabricated by physical methods, chemical bonding, sol-gel methods, or in situ growth. Toxic and harmful substances in foods and foodstuffs are efficiently extracted by exploiting the high adsorbent capacities and specificity of COPs. Future development prospects and challenges in sample pretreatment are also discussed herein. There is increased focus on the development of simple, efficient, and environment-friendly methods to synthesize COPs with specific functions; further, high-throughput, sensitive analytical methods may be established. In the future, more specific COPs will be prepared in a cost-effective manner for widespread use in sample pretreatment.

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Recent developments of pesticide adsorbents based on cyclodextrins ZHANG Jinfeng, LI Ping, MA Jiutong, JIA Qiong 2021, 39 (2):  173-183.  DOI: 10.3724/SP.J.1123.2020.08018 Abstract ( 144 )   HTML ( 21 )   PDF (2065KB) ( 120 )   The invention and application of pesticides have greatly increased the yield of crops, greatly contributing to ensuring people’s basic livelihoods and gradually improving their livelihoods to a well-off level. However, foods, water sources, and soil, containing high levels of pesticide residues, result in increasingly serious pollution. Pesticide residues usually have the characteristics of micro toxicity, difficult biodegradation, and bioaccumulation, and thus pose serious threat to living organisms and ecosystems. In recent years, pesticide pollution has earned worldwide focus. Thus, methods for the efficient detection of trace pesticides and reduction of the harm caused by pesticide pollution are urgently required. Researchers have used catalysis, electrochemistry, membrane separation, adsorption, and other methods to enrich pesticides from complex matrices. Among these, adsorbents have attracted much attention owing to their advantages of simple operation steps, rapid treatment process, and low amounts of organic solvents required. Research on adsorption materials has always been a very active field, and is also the key to the success of separation and enrichment of pesticides from complex matrices. Development of adsorbents with the advantages of simple synthesis, environment-friendliness, high stability, and strong reusability is of great significance. There has been some progress in the field of pesticide adsorption using supramolecular compounds. Cyclodextrin is a macrocyclic compound with a cavity after crown ether, which can form inclusion complexes via host guest interactions as the main body. Cyclodextrin can also be modified by etherification, esterification, oxidation, and other chemical reactions to improve its adsorption performance. Pesticides can be classified into organic and inorganic substances. One of the most widely used inorganic fungicides is the Bordeaux solution, whose main component is Cu2+. Organic fungicides, insecticides, herbicides, and plant growth regulators are basically organic molecules, whose hydroxyl and carboxyl groups can form complexes with Cu2+. As a matrix, cyclodextrin not only increases the surface area of the materials, but also provides the binding sites of hydroxyl and carboxyl groups, which guarantees efficient enrichment of Cu2+. Organic pesticides with high polarity, high electron density, and strong hydrophobicity could be better adsorbed. In this paper, the application of cyclodextrin-based adsorbents in pesticide adsorption was reviewed, and on this basis, reference to future development directions and application prospects were provided. The adsorption capacity of individual pesticide adsorbents based on cyclodextrin, as reviewed in this paper, is not high enough. Therefore, improving the adsorption capacity is currently a major research target. Some of the above-mentioned adsorbents have unclear degradation mechanisms and can easily cause secondary pollution. Therefore, the development of environment-friendly pesticide adsorbents that are easy to regenerate is a promising research direction for the future. After adsorption, some detection methods are used to determine whether the pesticide residues are up to the standard; however, the detection instruments are expensive. Therefore, the development of a combined detection mechanism that can reduce workload and cost is a promising research direction. Finally, the development of smart cyclodextrin-based adsorbents is also an efficient and rapid method to reduce the cost of detecting residual pesticide concentrations and the risk of pesticide pollution. For example, intelligent materials, whose color changes can be observed by the naked eye, not only adsorb pesticides, but also respond according to the concentration of residual pesticides.

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Perfluoroalkyl and polyfluoroalkyl substances in eggs: analytical methods and their application as pollutant bioindicator YE Tong, CHEN Yu, FU Jie, ZHANG Aiqian, FU Jianjie 2021, 39 (2):  184-196.  DOI: 10.3724/SP.J.1123.2020.09023 Abstract ( 146 )   HTML ( 23 )   PDF (4012KB) ( 217 )   Perfluoroalkyl and polyfluoroalkylated substances (PFASs) are environmentally persistent and biomagnified along food chains. They have been widely detected globally, even in the human body, and their potential toxicity has attracted great attention. Eggs are the origin of new life of ovipara and are rich in nutrients, thus they serve as one of the main protein sources for humans. Therefore, the level of pollutants in eggs can affect the reproduction of ovipara, and it is also related to human health by food intake. In recent years, poultry egg samples have been widely used in the assessment of biological and ecological pollution as a non-invasive biota matrix. At the same time, recent studies have used eggs to evaluate the developmental toxicity and associated health risks based on the pollutant levels in egg samples. In this study, the methods of sample pretreatment and instrumental detection of PFASs for egg samples are summarized. In addition, the application of eggs as a pollutants bioindicator of PFASs contamination has been discussed.

Articles

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Integrated multi-column two-dimensional liquid chromatographic system for determination of amisulpride in serum WANG Fenglin, YANG Sandong, ZHOU Xinying, FENG Jiao, TANG Tao, LI Tong 2021, 39 (2):  197-202.  DOI: 10.3724/SP.J.1123.2020.07035 Abstract ( 107 )   HTML ( 27 )   PDF (1111KB) ( 82 )   Amisulpride is a clinically effective antipsychotic drug. It has been recommended for therapeutic drug monitoring in Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology. An integrated multicolumn two-dimensional liquid chromatography system was constructed. Two reversed-phase columns, Supersil ODS2 (150 mm×4.6 mm, 5 μm) and SinoChrom ODS-BP (150 mm×4.6 mm, 5 μm), with different hydrophobicities were employed in the first and second separation dimensions, respectively. A strong cation-exchange short column, Supersil SCX (10 mm×4.6 mm, 5 μm) was used to trap samples after the first dimensional separation. A two-position six-port valve was applied to change the flow path for transferring the samples. An auxiliary pump was used to change the mobile phase between the first dimensional column and the trapping column. An intact method for analyzing amisulpride in serum was developed using an integrated multicolumn two-dimensional liquid chromatography system. Serum samples were pretreated only by protein precipitation and centrifugation. In the protein precipitation step, a mixture of perchloric acid (6%, v/v) and methanol was used as the precipitation reagent, whose volume was three times that of the serum sample. The use of this reagent helped eliminate the obvious solvent effects resulting from the large injection volume (300 μL). Then, the samples were vortexed for 2 min and centrifuged for 5 min at a velocity of 10000 r/min. The supernatant was injected into the system directly. Acetonitrile/phosphate buffer (25 mmol/L, pH 3.0; 20∶80, v/v) and acetonitrile/phosphate buffer (25 mmol/L, pH 7.0; 25∶75, v/v) were used as mobile phases for the first and second dimensions, respectively, at a flow rate of 1 mL/min. The solvent strength and pH of the first dimensional eluent were adjusted at the two-dimensional chromatographic interface. Phosphate buffer (25 mmol/L, pH 3.0) was supplied at a rate of 1 mL/min by the auxiliary pump for adjustment. The adjustment process allowed amisulpride to remain cationic, thus leading to improved transfer and trapping efficiencies in strong cation-exchange columns, in the heart-cutting mode. The trapping time was determined to be between 4 and 5 min by a confirmation experiment. The use of a short trapping column and the appropriate mobile phase conditions allowed us to complete the analysis within 12 min. The established method was validated in detail by investigating the linearity, limit of detection (LOD), limit of quantification (LOQ), and recovery. A good linear relationship was observed between 10 and 200 ng/mL (r=0.9998). The LOD and LOQ were 7.28 ng/mL and 24.27 ng/mL, respectively. The high sensitivity of the validated method met the requirements of the therapeutic reference range of the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology. The recovery of amisulpride spiked in a serum sample at 50 and 100 ng/mL were stabilized between 73.7% and 76.8%, which revealed the good stability of the established method. As opposed to the complicated traditional analytical methods, our method based on the automated integrated system is cost-effective and low-maintenance, thus being appropriate for routine therapeutic drug monitoring in clinical research. Moreover, our method is highly promising as the system cost is much lower than that of the popular LC-MS, while the capacity is sufficient for the determination of drugs in serum.