Stroke is a major cause of mortality and long-term disability worldwide. The study of biomarkers and pathogenesis is vital for early diagnosis and treatment of stroke. In the present study, a continuous-flow normal-phase/reversed-phase two-dimensional liquid chromatography–quadrupole time-of-flight mass spectrometry (NP/RP 2D LC-QToF/MS) method was employed to measure lipid species in human plasma, including healthy controls and lacunar infarction (LI) patients. As a result, 13 lipid species were demonstrated with significant difference between the two groups, and a “plasma biomarker model” including glucosylceramide (38:2), phosphatidylethanolamine (35:2), free fatty acid (16:1), and triacylglycerol (56:5) was finally established. This model was evaluated as an effective tool in that area under the receiver operating characteristic curve reached 1.000 in the discovery set and 0.947 in the validation set for diagnosing LI patients from healthy controls. Besides, the sensitivity and specificity of disease diagnosis in validation set were 93.3% and 96.6% at the best cutoff value, respectively. This study demonstrates the promising potential of NP/RP 2D LC-QToF/MS-based lipidomics approach in finding bio-markers for disease diagnosis and providing special insights into the metabolism of stroke induced by small vessel disease.

Ambient mass spectrometry facilitates surface detection under ambient conditions and has quickly found its applications in various areas. However, the sensitivity of AMS methods is usually not as good as that of encapsulated ion sources due to less efficient ion transmission. In this work, a briefly machined external ion funnel (three-pole electrostatic lens) was adopted and installed between direct analysis in real time and the mass spectrometer inlet to increase detection sensitivity. Software investigation with SIMION version 8.0 was employed to calculate electric fields and to simulate the trajectories of charged particles in the electric field. Both the geometrical parameters of the ion funnel and the electric parameters were studied to obtain the optimal ion focusing results, which demonstrated the ion funnel equipment would greatly improve the ion transmission efficiency. The equipment showed good prospect in direct analysis in real time-mass spectrometry analysis in the future.

We herein present a porphyrinic metal–organic framework (MOF) as a highly sensitive fluorescent probe targeting Cu(II) ions with a fast response. The well-isolated nature of porphyrin moieties within the framework greatly enable accessible recognition sites, which leads to an outstanding detection limit performance of 67 nM among MOF-based materials.

To explore underlying molecular mechanisms and identify novel lipid biomarkers promising for colorectal cancer (CRC) diagnosis, a continuous-flow two dimensional liquid chromatography–quadrupole time-of-flight mass spectrometry (2D LC-QToF/MS) method was employed to comprehensively measure lipid species in human plasma of CRC patients and healthy controls. With a total of 427 annotated lipid species, we identified 64 lipid species with corrected p value less than 0.05 and fold change more than 1.5. These significantly altered lipid species were mainly involved in glycerolipids and glycerophospholipids metabolism and sphingolipids metabolism. After the diagnosis ability evaluation based on the receiver operating characteristic (ROC) curve, phosphatidylglycerol (34:0), sphingomyelin (42:2), ceramide (44:5), lysophosphatidylcholine (18:3), lysophosphatidylcholine (18:2), phosphatidylethanolamine (O-36:3), phosphatidylethanolamine (O-38:3) and sphingomyelin (38:8) were finally proposed as the potential biomarkers with the area under the curve (AUC) more than 0.900. These results suggest that this 2D LC-QToF/MS-based lipidomics profiling has great potential as a noninvasive diagnostic method in detecting CRC and hopefully provide new clues to understand its underlying mechanism.

•158 PUFA and their metabolites in serum were analyzed by UPLC-MS/MS.•Serum lipidome give me a comprehensive map of PUFAs metabolite in the process of CRC.•Five PUFA metabolites were used as a potential biomarker of CRC.The biomarker identification of cancer is benefit for early detection and less invasion. Polyunsaturated fatty acid (PUFA) metabolite as inflammatory mediators can affect progression and treatment of cancer. In this work, the serum was collected from colorectal cancer patients and healthy volunteers, and then we tested the change of serum PUFA metabolites in both of them by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Of the 158 PUFA and their metabolites, we found that abnormal change of 2, 3-dinor-8-iso-PGF2α, 19-HETE and 12-keto-LTB4 from arachidonic acid were observed in colorectal cancer patients. Meanwhile, 9-HODE and 13-HODE from linoleic acid were significant lower in colorectal cancer patients. Our data suggested that some PUFA metabolites might be used as a potential biomarker of colorectal cancer, which might provide assistance in clinical diagnosis and treatment.

Open image in new windowMetabolomics has become a valuable approach to discover novel biomarkers and to increase the mechanistic understanding of many deceases, while lipidomics is one of the hottest points of research areas related to metabolomics, which attracted dramatic attention during the past years. Therefore, this special issue focuses on the analytical methods for metabolomics and lipidomics to provide our readers with recent developments in these areas. Eight papers collected here are contributed by some excellent groups from different countries and the contents cover entire range of metabolomics research, including method development, data processing and applications.Dr. González-Domínguez and coworkers from Universidad de Huelva, Spain, explore the utility of metabolomics based on direct infusion mass spectrometry (MS) for analyzing blood samples. The most important analytical concerns to be considered are discussed, including sample handling, comprehensive fingerprinting, and subsequent identification of metabolites and global characterization of metabolomic profiles. As an example, a brief review on the application of these metabolomic platforms in Alzheimer’s disease research is also provided. Prof. Moon, et al. from Yonsei University, Korea, reviewed the techniques of off-line and on-line coupling of flow field-flow fractionation with MS for the analysis of blood plasma lipoproteins, and the processes of bottom–up and top–down approaches. While both methods aim to quantify the lipids within lipoproteins, the bottom–up approach provides an extensive lipidome, whereas the top–down method is suitable for high speed targeted lipidomic analysis.As well known, separation and identification of lipid molecules is of great significance and remains challenging because of the existing of many lipid isomers. The separation of lipid isomers by supercritical fluid chromatography (SFC) has received more and more attention, and Dr. Bai and her coworkers from Peking University briefly introduces the principle of SFC and its applications in lipid isomer separation. Dr. Ding’s group from China Pharmaceutical University discussed the noninvasive detection and imaging of matrix metalloproteinases for cancer diagnosis. It is concluded that the probes designed for matrix metalloproteinase detection commonly have two features. One is off-then-on state in detection signal, and another is specific retention upon sensing matrix metalloproteinases. The development of theory and technology for biomarker probe design will be beneficial to the accurate diagnosis and effective treatment of cancers.In addition, the data preprocessing in metabolomics based on untargeted liquid chromatography (LC)–MS was summarized by Dr. Shui and his co-authors from Chinese Academy of Sciences, providing a brief introduction to the general steps of processing for raw MS data, and automated data processing tools. Then, characteristics of mainly free data preprocessing software were compared for researchers’ consideration in conducting metabolomics study.As for the applications of metabolomics analysis, Prof. Cai’s group used LC-orbitrap MS for the profiling analysis of small metabolites in mice serum and striatum exposed to 2,2′,4,4′-tetrabromodiphenyl ether. 57 differential metabolites that significantly altered in mice serum and striatum were identified through databases searching and authentic standards confirmation. On the basis of metabolic variations, molecular mechanisms including disturbance of dopaminergic system, neurotransmitters regulation, DNA methylation and oxidative stress were proposed. In past 12 years, my lab has made some efforts on the method development and applications of lipidomics isn clinical study. A continuous-flow normal-phase/reversed-phase two dimensional LC-quadrupole time-of-flight MS (NP/RP 2D LC/QTOF-MS) method has been developed for profiling analysis of lipid species, and is now used for lipidomics study on human plasma from hepatocellular carcinoma (HCC) patients and healthy controls. 23 lipid species with corrected p value <0.05 and fold change >1.5 were proposed as potential lipid biomarkers for HCC. On the other hand, sphingolipids profiling of plasma in patients with diabetes mellitus associated with atherosclerosis was carried out by a novel normal-phase ultrahigh performance LC/QTOF-MS method, resulting in shorter analytical time, with better or comparable sensitivity for sphingolipids analysis, compared to previous NP/RP 2D LC/QTOF-MS method. 12 sphingolipids species were identified, and the isomers of glucosylceramides and galactosylceramides were successfully separated. It was found that 5 GluCs, rather than GalCs, were included in these 12 potential biomarkers, indicating that there may be some extra activation pathways of diabetes mellitus associated with atherosclerosis, different from the atherosclerosis pathway and the diabetes mellitus pathway, causing cardiovascular disease.Finally, I would like to express my sincere thanks to all the contributors to this special issue, and all referees are appreciated for their careful review on the submitted manuscripts. We believe that the content of this issue is helpful to our readers involved in research areas of metabolomics and lipidomics. Journal of Analysis and Testing as a new journal will provide an international academic platform for the publication of original research papers, rapid communications and critical reviews in all aspects of fundamental and applied analytical chemistry. We hope that our colleagues will share our enthusiasm and vision continuously.Huwei LiuProfessor in Analytical Chemistry

Hepatocellular carcinoma (HCC) accounts for the major primary liver cancer, and its morbidity and mortality rates are very high. Identification of novel biomarkers for the early diagnosis and treatment of this disease is of crucial importance. In this study, a continuous-flow normal-phase/reversed-phase two-dimensional liquid chromatography—quadrupole time-of-flight mass spectrometry (NP/RP 2D LC-QToF/MS) method was used to detect lipid species in human plasma from HCC patients and healthy controls. As a result, the two groups were clearly separated by principal component analysis. Besides, 23 lipid species with corrected p value <0.05 and fold change >1.5 were proposed as potential lipid biomarkers for HCC. Among them, 9 lipid species, including galactosylceramide (36:5), free fatty acid (20:4), phosphatidylethanolamine (40:6), phosphatidylethanolamine (38:6), diacylglycerol (40:5), diacylglycerol (44:2), lactosylceramide (40:3), phosphatidylcholine (40:6), and free fatty acid (22:5), exhibited excellent ability to distinguish HCC patients from healthy controls with the area under the receiver-operating characteristic curve >0.900, showing promising clinical value. Taken together, these results indicate the great potential of NP/RP 2D LC-QToF/MS method in disease diagnosis, which might be helpful in clinical practice.

A novel normal-phase UPLC-QToF MS method was developed for sphingolipids analysis, which was then applied to separate and identify seven classes of sphingolipids in plasma. The time-consuming of this novel method was much shorter than previous 2D LC–MS method, while the sensitivity, repeatability and resolution for sphingolipids analysis were better or comparable. Besides, the differences of lipids in human plasma among diabetes mellitus patients, diabetes mellitus associated with atherosclerosis patients and control subjects were also compared. Finally, 12 sphingolipids species were identified as the amounts of which in diabetes mellitus associated with atherosclerosis patients were significantly higher than them in diabetes mellitus patients (VIP >1.0, p value <0.05, fold change >1.5). As the isomers of GalCs and GluCs were successfully separated, it was found that five GluCs, rather than GalCs, were included in these 12 potential biomarkers. These results suggest the need to separate GalCs from GluCs, and also indicated that there may be some extra activation pathways of diabetes mellitus associated with atherosclerosis, different from the atherosclerosis pathway and the diabetes mellitus pathway, causing cardiovascular disease.

A bifunctional affinity probe NiCoMnO4 was designed and prepared with controllable morphology and size using facile methods. It was observed that the probe could be applied in His-tagged proteins purification and phosphopeptides enrichment simply through the buffer modulation. NiCoMnO4 particles showed satisfactory cycling performance for His-tagged proteins purification and broad pH-tolerance of loading buffer for phosphopeptides affinity. Therefore, a high-throughput, cost-effective, and efficient protein/peptide purification method was developed within 10 min based on the novel bifunctional affinity probe.

A novel carboxyl-functionalized metal–organic framework for highly efficient uranium sorption was prepared through a generic postsynthetic strategy, and this MOF’s saturation sorption capacity is found to be as high as 314 mg·g–1. The preliminary application illustrated that the grafted free-standing carboxyl groups have notably enhanced the sorption of uranyl ions on MIL-101. In addition, we have performed molecular dynamics simulation combined with density functional theory calculations to investigate the molecular insights of uranyl ions binding on MOFs. The high selectivity and easy separation of the as-prepared material have shown tremendous potential for practical applications in the nuclear industry or radioactive water treatment, and the functionalized MOF can be extended readily upon the versatility of click chemistry. This work provides a facile and purposeful approach for developing MOFs toward a highly efficient and selective extraction of uranium(VI) in aqueous solution, and it further facilitates the structure-based design of nanomaterials for radionuclide-containing-medium pretreatment.Keywords: DFT calculation; metal−organic frameworks; molecular dynamics simulation; postsynthetic strategy; radioactive water treatment; uranium extraction

The online combination of surface plasmon resonance (SPR) with mass spectrometry (MS) could be beneficial for accurately acquiring molecular interaction data simultaneously with their structural information at high throughputs. In this work, a novel SPR-MS interface was developed using a dielectric barrier discharge ionization (DBDI) source. The DBDI source was placed in front of the MS inlet, generating an ionization plasma jet. A spray tip was set between the DBDI source outlet and the MS inlet, nebulizing the SPR sample solution. Using this interface, samples could first be studied by SPR, then sprayed and ionized, finally analyzed by MS. By analyzing model samples containing small-molecule drugs dissolved in salt containing solutions, the practicability of this SPR-DBDI-MS interface was proved, observing the consistent change of SPR and MS signals. Compared with our previously developed direct analysis in real time (DART) based SPR-MS interface, this new interface exhibited a higher and better tolerance to non-volatile salts, and different ionization capabilities for various samples. These results indicated that the interface could find further utilization in SPR-MS studies especially when physiological conditions were needed.

•A 3D magnetic homochiral metal-organic frameworks was prepared using a facile method.•Based on it, a rapid and efficient phosphopeptide enrichment method was developed using magnetic solid phase extraction within 10 min.•Efficient and highly selective capture of phosphopeptides from tryptic digests and human serum was obtained.•Fe3O4@ZnBLD particles showed satisfactory reproducibility of the synthesis and could be reused for at least seven times.Enrichment of phosphopeptides based on various affinity probes prior to mass spectrometry detection is usually required due to the low abundance and low ionization efficiency of phosphopeptides. In this work, a 3-dimentional homochiral metal-organic frameworks (MOFs) was modified with magnetic nanoparticles using a facile method and then utilized for phosphopeptides capture with high efficiency and specificity. Based on magnetic solid phase extraction, a rapid and efficient method was developed and the whole enrichment procedure could be easily finished within 10 min. Efficient and highly selective capture of phosphopeptides from tryptic digests and human serum was achieved. This affinity probe showed satisfactory reproducibility of the particle synthesis and could be recycled for at least seven times. With all the advantages mentioned above, this strategy is of great potential for routine application in phosphoproteomes.

Magnetic functionalized homochiral metal–organic frameworks (MOFs) were prepared and applied to efficient enantioselective fishing of chiral drug intermediates. Under optimized conditions, the enantiomeric excess (ee) value as high as 85.2% was achieved for methyl phenyl sulfoxide (MPS) within 3 min.

A polymer monolith microextraction (PMME) procedure coupled to plasma assisted laser desorption ionization mass spectrometry (PMME-PALDI-MS) was developed for rapid and organic solvent-free trace analysis. The extraction device used a “Dip-it” sampler coated with a MWNT incorporated monolith, and the analytes adsorbed on monoliths were effectively desorbed by laser, improving detection sensitivity.

The online coupling of surface plasmon resonance (SPR) with mass spectrometry (MS) has been highly desired for the complementary information provided by each of the two techniques. In this work, a novel interface for direct and online coupling of SPR to direct analysis in real time (DART) MS was developed. A spray tip connected with the outlet of the SPR flow solution was conducted as the sampling part of the DART-MS, with which the online coupling interface of SPR-MS was realized. Four model samples, acetaminophen, metronidazole, quinine, and hippuric acid, dissolved in three kinds of common buffers were used in the SPR-DART-MS experiments for performance evaluation of the interface and the optimization of DART conditions. The results showed consistent signal changes and high tolerance of nonvolatile salts of this SPR-MS system, demonstrating the feasibility of the interface for online coupling of SPR with MS and the potential application in the characterization of interaction under physiological conditions.

A planar tetracoordinated oxygen containing a homochiral metal–organic framework (MOF) has been synthesized and characterized that can be used as a new chiral stationary phase in high-performance liquid chromatography to efficiently separate racemates such as pharmaceutically important (±)-ibuprofen and (±)-1-phenyl-1,2-ethanediol.

A simple direct analysis in a real time-mass spectrometry (DART-MS) method was developed for the rapid determination of four Sudan dyes (I–IV) in chili powder. Simple liquid extraction by hexane without further clean-up was used for sample preparation. DART parameters were systematically optimized to achieve the best detection performance. A DIP-it sampler was used for automatic sampling. The matrix effect was measured by comparing the limit of detection (LOD) in matrix solution with that in pure organic solution. Eventually, the identification of the Sudan dyes was confirmed by MS/MS results and the LODs for four analytes in matrix solution were ∼0.5 μg mL−1. The method showed good linearity with correlation coefficients (R2) greater than 0.99 for concentrations ranging from 1 to 20 μg mL−1. The whole analytical process could be completed within 15 minutes with good recoveries (88–116%) and satisfactory repeatability (<26%, n = 3).

•Principles and strategies for identification of unknowns using Q-TOF-MS.•Q-TOF-MS-based metabolomics approach to quality control of TCM in detail.•Q-TOF-MS-based metabolomics research for disclosing the intervention mechanism of TCM.•Q-TOF-MS-based metabolomics research for disclosing the toxicity mechanism of TCM.Traditional Chinese medicine (TCM) has been effective in prevention and treatment of chronic diseases in a synergic manner with mild healing effects and lower side effects than Western medicines. Researchers have made great efforts to explore the real theory of TCM for many years with different strategies. With the rapid advances in instrumentation in chromatography and mass spectrometry, more scientific outcomes have been achieved for disclosing the mysteries of TCM. In this article, we review the achievements of quadrupole time-of-flight mass spectrometry in TCM analysis, including profiling active ingredients and their metabolites, screening harmful components, and applying cutting-edge metabolomics strategies.

A lithium-rich composite metal oxide was evaluated as a novel matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). The low background interference and lithium-rich feature made it a highly efficient matrix for the analysis of small molecules with high reproducibility, sensitivity and strong salt tolerance.

Lipids are important components of cell membranes and thylakoids in cyanobacteria, and they play vital roles in various biological activities. Real-time tracing of the variation of membrane lipids can provide insights of the physiological status of cyanobacterial cells. In this work, easy ambient sonic-spray ionization mass spectrometry (EASI-MS) was utilized to investigate the changes of acidic lipids in unicellular (Synechocystis 6803, Synechococcus 7002) and filamentous (Anabaena 7120) cyanobacteria during different growth phases. A sqdX mutant with a reduced synthesis of sulfoquinovosyl diacylglycerol (SQDG) was constructed to verify the acquired data of EASI-MS. Principal component analysis (PCA) was performed to compare the acquired data, enabling the discrimination of different species of cyanobacteria in day-to-day analysis. The results showed that the three representative cyanobacteria and their growth status can be easily determined on the basis of the lipids components detected by EASI-MS. Very interestingly, significant decreases of the ratios of SQDG/PG and dramatic changes of the unsaturation level of lipids were observed in different culture times in these cyanobacteria, and these two unique characters can be used describe the aging of cyanobacteria.

Online coupling of in-tube solid phase microextraction (IT-SPME) with direct analysis in real time mass spectrometry (DART-MS) was realized for the first time and applied in the analysis of triazine herbicides in lake water and orange juice. We incorporated single-wall carbon nanotubes (SWNTs) into a polymer monolith containing methacrylic acid (MAA) and ethylene dimethacrylate (EDMA) to form a novel poly(methacrylic acid-co-ethylene dimethacrylate-co-single wall carbon nanotubes) (poly(MAA-EDMA-SWNT)) monolith, which was then used in IT-SPME for enrichment of six triazine herbicides from water samples. With the online combination of IT-SPME with DART-MS, the analytes desorbed from the monolith were directly ionized by DART and transferred into MS for detection, thus rapid determination was achieved. Compared with regular DART-MS method, this online IT-SPME-DART-MS method was more sensitive and reproducible, because of the IT-SPME procedures and the isotope-labeled internal standard used in the experiment. Six triazine herbicides were determined simultaneously using this method with good linearity (R2 > 0.998). The limit of quantification (signal-to-noise ratio of S/N = 10) of the six herbicides were only 0.06–0.46 ng/mL. The proposed method has been applied to determine triazine herbicides in lake water and orange juice, showing satisfactory recovery (85%–106%) and reproducibility (relative standard deviation of RSD = 3.1%–10.9%).

•A not-stop-flow online NP/RP 2D LC-MS method was developed for lipid profiling.•Overall, 540 endogenous lipid species from 17 classes were identified from human plasma.•This novel method showed high sensitivity (ng/mL grade) and good repeatability.•Successful separation of isomers of GalC and GluC was achieved.•The levels of GalC and GluC were different in human plasma from different subjects.A not-stop-flow online two-dimensional (2D) liquid chromatography (LC) method was developed for comprehensive lipid profiling by coupling normal- and reversed-phase LC with quadrupole time-of-flight mass spectrometry (QToF-MS), which was then applied to separate and identify the lipid species in plasma, making its merits in quality and quantity of the detection of lipids. Total 540 endogenous lipid species from 17 classes were determined in human plasma, and the differences in lipid metabolism products in human plasma between atherosclerosis patients and control subjects were explored in detail. The limit of detections (LODs) of 19 validation standards could all reach ng/mL magnitude, and the RSDs of peak area and retention time ranged 0.4–8.0% and 0.010–0.47%, respectively. In addition, a pair of isomers, galactosylceramides (GalC) and glucosylceramides (GluC), was successfully separated, showing that only the levels of GalC in atherosclerosis patients were significantly increasing, rather than GluC, compared with the controls (controls vs. patients: the ratio was 1.5–2.8-fold increasing). It would be helpful to the further research of the atherosclerosis.

ZnSn(OH)6 and binary-component SnO2–ZnSn(OH)6 were introduced as affinity probes for phosphopeptide enrichment for the first time. Two strategies, either ZnSn(OH)6 and SnO2 serial enrichment or binary-component SnO2–ZnSn(OH)6 enrichment in a single run, were proposed to enhance multi-phosphopeptide enrichment and to significantly improve global phosphopeptide detection.

The online coupling of capillary electrophoresis with ambient direct analysis in real time mass spectrometry (DART-MS) was realized by a coaxial tip interface. The analytes eluted from capillary electrophoresis (CE) were directly ionized by the metastable helium flux produced by DART and transferred into MS for the detection, with which the online separation and simultaneous detection were achieved. The CE-DART-MS can tolerate higher concentrations of detergents and salts than traditional CE-electrospray ionization (ESI)-MS and avoided the difficulties of collecting CE effluent and cleaning the interface, which simplified the experimental procedures and shortened the analysis time. The performance of the technique was successfully verified by capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) using a mixture of 4-aminoantipyrine, zolmitriptan, and quinine. This online technique showed good repeatability with the relative standard deviations (RSDs; n = 5) of 0.56–1.23% for the retention times and 2.01–7.41% for the peak areas. The quantitative analysis of 4-aminoantipyrine was accomplished in the range of 0.01–0.50 mg/mL with the linear correlation coefficient of 0.9995 and limit of detection of 14.7 fmol. Compared with CE-ESI-MS, the ion suppression effects of nonvolatile salts and detergents were efficiently minimized. The signal intensity remained constant when the concentrations reached 100 mM for sodium borate and 30 mM for SDS (in 30 mM sodium borate buffer). In addition, the proposed method was successfully applied to the detection of the endogenous caffeine in Chinese white tea.

The development of rapid screening and identification techniques is of great importance for drug discovery, doping control, forensic identification, food safety and quality control. Ambient mass spectrometry (AMS) allows rapid and direct analysis of various samples in open air with little sample preparation. Recently, its applications in high-throughput screening have been in rapid progress. During the past decade, various ambient ionization techniques have been developed and applied in high-throughput screening. This review discusses typical applications of AMS, including DESI (desorption electrospray ionization), DART (direct analysis in real time), EESI (extractive electrospray ionization), etc., in high-throughput screening (HTS).

•Novel monolithic material for online microextraction of 28-epihomoBR.•Online SPME–LC–MS for automated analysis of 28-epihomoBR in plant samples.•Lower LOD (2.0 ng/L) made it easy to detect analyte in only 400 mg plant sample.By on-line solid phase microextraction with polymer monolith coupled to liquid chromatography–mass spectrometry (SPME–LC–MS), an automated and sensitive method for analysis of the endogenous 28-epihomobrassinolide (28-epihomoBR) in Arabidopsis thaliana was developed in this work. Firstly, a poly(methacrylic acid-co-ethylene dimethacrylate) (poly(MAA-co-EDMA)) monolith was prepared in the capillary and applied in in-tube SPME. Polyethylene glycol (PEG) was used as porogen to adjust the specific surface area and hydrophobicity of the target monolith to get satisfactory permeability, high mechanical strength and good stability. The optimized monolith was then served as extraction medium for analysis of the derivatized 28-epihomoBR in plant samples with the cleanup of matrix and enrichment of desired analyte at the same time. Good linearity was obtained in the linear range of 5–500 ng/L with the coefficient of determination (R2) of 0.9996. The limit of detection (S/N = 3) of 28-epihomoBR was found to be 2.0 ng/L and the limit of quantification (S/N = 10) was 5.0 ng/L. Using this method, the endogenous 0.101 ng/g (FW) 28-epihomoBR was successfully detected from only 400 mg A. thaliana samples with satisfactory recovery (80.3–92.1%) and reproducibility (RSD 6.8–9.6%). Comparing with other sample pretreatment methods, this automated on-line SPME–LC–MS method is rapid, sensitive, reproducible and laborsaving.

•First time study of graphene matrix effects in open air conditions.•Graphene acts as an excellent medium for energy transfer.•Graphene is general and effective matrix for ambient MS.In this work, the signal intensity of ambient plasma assisted laser desorption ionization mass spectrometry (PALDI-MS) was significantly increased with graphene as matrix. The graphene functions as a substrate to trap analytes, absorb energy from the visible laser irradiation and transfer energy to the analytes to facilitate the laser desorption process. The desorbed analytes are further ionized by helium plasma and analyzed by MS. Compared with a traditional organic matrix, α-cyano-4-hydroxycinnamic acid (CHCA), graphene exhibited much higher desorption efficiency for most of the compounds benefitting from the strong optical absorption at 532 nm. The performance has been confirmed by the facile analysis of more than forty compounds with various structures. Additionally, this method was successfully applied to distinguish three kinds of Chinese tea leaves by detecting the endogenous caffeine and theanine, which proved the utility, facility and convenience of this method for rapid screening of main components in real samples.Graphical abstractThe signal intensity of ambient plasma assisted laser desorption ionization mass spectrometry (PALDI-MS) was significantly increased with graphene as matrix. This method has been proved to be utility, facile and convenient for rapid screening of main components in real samples.

An improved online two-dimensional liquid chromatography-quadrupole time-of-flight mass spectrometry (2D LC-QToF MS) system was developed for the lipid profiling of human plasma, in which different lipid classes were separated by the first dimensional normal-phase (NP) LC and different lipid molecular species were separated by the second dimensional reversed-phase (RP) LC. This 2D LC-QToF MS system was built based on a ten-port, two-position valve as the interface, the conditions of which had been optimized and discussed in detail. As two loops were used to trap and transfer the first dimensional elute to the second dimension separately, this new interface suppressed the sample band broadening in the first dimensional column, increased the recovery and repeatability of 2D LC interface, and offered the possibility for the realization of not-stop-flow NP/RP 2D LC system. Finally, 190 endogenous lipid species out of 10 lipid classes were determined within a single run from the plasma of peritoneal patients. This method was also applied to identify the difference in lipid profile between plasma from peritoneal dialysis patients with bad volume status and peritoneal dialysis patients with good volume status. The discovery of 30 potential biomarkers would be helpful to the malnutrition, inflammation, and atherosclerosis syndrome investigation.

In this work, an extremely simple and quite sensitive mass spectrometric method termed ambient surface-assisted laser desorption/ionization mass spectrometry (ambient SALDI-MS) was developed to analyze different kinds of compounds, just using a piece of graphite-coated paper for the sample introduction. This provides great advantage in simplifying the analysis process. The method is quite easy to use, and there is no need to worry about the source of graphite, that is, the brands or the types of pencil. And the whole process was carried out under atmospheric pressure, offering all the merits that could occur in ambient MS. The improved sensitivity of this method is mainly because of the graphite, which serves as energy-transfer medium to absorb the energy of the photons and release it to the analytes that are adsorbed on the graphite surface. Also, three different laser wavelengths (1064, 532, and 355 nm) was tested to investigate the desorption mechanism. Fifty-one compounds, with varied chemical structures, were tried to prove that this new method possessed universal applicability to detect different kinds of small organic molecules.

Jasmonic acid (JA) is an essential plant hormone involved in plant development and defense system. There are four stereoisomeric forms of JA and they act quite differently in vivo. In this work, a normal phase liquid chromatography–quadrupole time-of-flight mass spectrometry (NPLC–QTOF-MS) method using cellulose tris (4-methylbenzoate) coated silica gel as the chiral stationary phase was first established for the simultaneous discrimination and direct analysis of all the four JA stereoisomers without need of derivatization. A non-endogenous JA stereoisomer was introduced as the internal standard to ensure the reliability of the developed method. Satisfactory results were obtained in terms of sensitivity (limit of detection, 0.5 ng mL−1 or 2.4 fmol), linearity (R2 = 0.9996) and repeatability (run-to-run RSD of migration time and peak area, 0.37% and 5.9%, respectively, n = 6). Endogenous rise of two natural JA stereoisomers was detected in tobacco leaves and their variations in response to mechanical wounding were monitored. In addition, the configurational stability of JA stereoisomers was investigated using the stereoisomerically pure forms which were not commercially available but easily obtained by our semi-preparative chiral LC method. Experimental evidence indicated that both of the two naturally existing JA stereoisomers were putative signals for wounding response, and the epimerization between them was not a spontaneous process simply promoted by the thermodynamical instability as expected before.Highlights► Direct analysis of four JA stereoisomers by LC–QTOF-MS without derivatization. ► A non-endogenous JA stereoisomer as internal standard to ensure the reliability. ► Endogenous rise of two natural JA stereoisomers was detected in tobacco leaves. ► The variations of JA amount in response to mechanical wounding were monitored. ► The configurational stability of JA stereoisomers was further investigated.

Chirality is an important, universal phenomenon in nature. For the in-depth study of pharmacology and biology, efficient enantioselective technologies are indispensable. Nanomaterials with large surface-to-volume ratio and specific physical and chemical properties have demonstrated great potential in chiral discrimination. Many publications show that utilization of nanomaterials could improve the selectivity, the stability and the efficiency of enantioseparation.This review summarizes the applications of various enantioselective nanomaterials, including mesoporous silica, organic polymers, metal-organic frameworks, metal nanomaterials, magnetic nanomaterials, carbon nanotubes and well-oriented chiral nanolayers. After proper preparation and modification, these functionalized nanomaterials are effective for chiral separation through their specific enantioselective adsorption, especially when they are used as stationary or pseudo-stationary phases in chiral chromatographic separation, such as thin-layer chromatography, high-performance liquid chromatography, gas chromatography and capillary electrophoresis.Highlights► Applications of nanomaterials in enantioselective technologies are summarized. ► Nanomaterials could improve the selectivity of enantioselective technologies. ► Nanomaterials could improve the stability of enantioselective technologies. ► Nanomaterials could improve the efficiency of enantioselective technologies. ► Magnetic materials help speed, simplicity and cost-effectiveness of enantioselection.

We developed a “continuous” trifluoroacetic acid (TFA) remover based on electrodialysis with bipolar membrane for online coupling of liquid chromatography (LC) and electrospray ionization mass spectrometry (ESI-MS) using TFA containing mobile phase. With the TFA remover as an interface, the TFA anion in the mobile phase was removed based on electrodialysis mechanism, and meanwhile, the anion exchange membrane was self-regenerated by the hydroxide ions produced by the bipolar membrane. So the remover could continuously work without any additional regeneration process. The established LC-TFA remover-MS system has been successfully applied for the qualitative and quantitative analysis of small molecules as well as proteins.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) with one chiral center at the carbinol is a major metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). As tobacco specific N-nitrosamines (TSNAs), NNK and NNAL are the most pulmonary carcinogens in tobacco products and smoke. In this paper, a chiral CE method modified with highly sulfated β-cyclodextrin (S-β-CD) was developed to investigate the stereoselective formation of NNAL from NNK in vitro in normal human bronchial epithelial (NHBE) cells. Combined with solid phase extraction (SPE) of the cell samples, NNK and NNAL enantiomers were baseline separated under the proposed CE conditions, with satisfactory recoveries (72.5–113% for NNK and (±)-NNAL) and low limits of detection (LOD, 2.5–3 μg/mL for NNK and (±)-NNAL). The cytotoxicity of NNK in NHBE cells was investigated through the cell counting kit (CCK) assay and proved to be highly dependent on the NNK's concentration. The metabolic results obtained from CE analysis demonstrated that NNK was preferentially metabolized to (+)-NNAL through carbonyl reduction. Meanwhile, the ratio of [(+)-NNAL]/[(−)-NNAL] was independent of NHBE cells’ incubation time with NNK, but could be changed according to the original incubation concentration of NNK. This chiral CE method could be useful for the study on toxicology and metabolic transformations of related TSNAs.

In this paper, we propose a rapid capillary zone electrophoretic method with dynamically coated capillaries for separation of and screening for six tobacco-specific nitrosamines, a group of strong carcinogens found only in tobacco products. Dynamic coating of the capillary surface with a polycation coating (CElixir Reagent A) followed by a polyanion coating (CElixir Reagent B; pH 2.5) was accomplished by use of a commercially available reagent kit. With this method, six tobacco-specific nitrosamines: N′-nitrosonornicotine, N′-nitrosoanatabine, N′-nitrosoanabasine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and 4-(methylnitroamino)-4-(3-pyridyl)-1-butanol were simultaneously separated and determined within 3 min, with a satisfactory detection limit of 1.0 μg mL−1 for all the tobacco-specific nitrosamines at S/N = 3, and a linear relationship between UV absorbance and analyte concentration (R2 > 0.98). The repeatability of the method ranged from 0.24 to 0.73% (RSD, n = 5) for migration time and 0.25–1.54% (RSD, n = 5) for peak area, demonstrating that this capillary electrophoretic method is better than conventional capillary zone electrophoresis.

Systemins are a class of systemic wound polypeptide hormones that play a central role in mediating defenses against pest attacks and other woundings. It has been desired to develop a sensitive and accurate determination method to monitor trace systemins in plants for the better understanding of molecular mechanisms of the polypeptide hormones. A superior method for accurate identification and quantitative determination of trace systemins in Solanaceous plants is described in this work, which is based on immunoaffinity column (IAC) purification and enrichment followed by liquid chromatography online coupled to electrospray quadrupole time-of-flight mass spectrometry (LC/ESI QTOF MS). The specific antitomato systemin polyclonal antibody had been produced and immobilized on a CNBr-activated Sepharose stationary phase. The prepared IAC was utilized for the extraction and enrichment of tomato systemin (TomSys), potato systemin (PotSys I and PotSys II), pepper systemin (PepSys), and nightshade systemin (NishSys) from Solanaceous plants. Subsequent identification and determination by LC/ESI QTOF MS revealed that the IAC enables efficient and specific enrichment of PotSys I, PotSys II, and especially TomSys. Under the optimized conditions, the developed method was successfully applied in the determination of TomSys in tomato leaves and PotSys I and PotSys II in potato leaves, and it offers detection limits (LODs, S/N =3) of 29, 72, and 135 pg/g and mean recoveries of 92.9%, 56.7%, and 34.8% at three concentrations (1.0, 2.0, and 4.0 ng/g) for TomSys, PotSys I, and PotSys II, respectively.

Phytohormones are key regulators in various physiological processes of plant growth and development. To better understand their regulatory actions, fast, sensitive and accurate methods for phytohormone analysis are critically required, and great efforts have been invested in this field. In this review, recent advances and developments in phytohormone determination strategies are presented, in terms of sample preparation and analytical approaches. Many types of analytical techniques are involved, including chromatography, mass spectrometry, immunoassay and others. Some challenges and prospects are also discussed.

In this paper, a micellar electrokinetic chromatography (MEKC) method combined with cation-selective exhaustive injection (CSEI) and sweeping was developed to separate and concentrate four tobacco-specific N-nitrosamines (TSNAs) including N′-nitrosoanabasine (NAB), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL). Experimental parameters affecting separation efficiency and enhancement factors were investigated in detail. Under the optimum MEKC condition, NAB, NNK, NNAL and iso-NNAL were baseline separated with high separation efficiencies and good peak shapes. Furthermore, with the preconcentration by CSEI–sweeping–MEKC, the sensitivity enhancement factors for NAB, NNK, NNAL and iso-NNAL in terms of peak areas ranged from 6.0 × 103 to 1.5 × 104, and the detection limits (LOD, S/N = 3) of four TSNAs were in the range of 0.004–0.016 μg/mL. In addition, this method had fairly good repeatability, and the RSDs of retention time and peak area were less than 1% and 5%, respectively. Finally, this method showed promising capabilities in the application of detecting and analyzing TSNAs in human urine samples.

The fragmentation pathways of two isomers of brassinosteroids, 28-homobrassinolide (28-h-BL) and 28-epihomobrassinolide (28-eh-BL), have been investigated by tandem mass spectrometry (MSn, n = 1, 2, 3, 4) with the electrospray ionization (ESI) source. The ESI mass spectrometric fragmentation pathways of protonated 28-h-BL and 28-eh-BL were comprehensively elucidated, and the principles revealed in this investigation could potentially be used to identify and distinguish brassinosteroids and their isomers.

Five naturally bioactive compounds, belonging to the representative flavonoid and pentacyclic triterpenoid types, were separated by liquid chromatography and analyzed on-line with negative ion ESI–MS. Rutin, quercetin, and oleanolic acid in the extracts of Rosa multiflora Thunb. of China were identified by the comparison of their retention times and mass spectrometric data with those of authentic standards, and their contents were 0.22, 3.8, and 45 µg g−1 of dry weight in rose hips, respectively. Five standards, including rutin, quercetin, kaempferol, lysionotin, and oleanolic acid were investigated by MS3, which facilitate further understanding of their structures.

We designed and fabricated a novel microdevice to facilitate continuous adsorption phenomena for biological sample preparation. Using the device, we also developed an online, highly integrated, multifunctional strategy, with a promise of accepting a large volume of crude tissue extracts with the end point generation of a reliable MS identification within 20 min. Under an external electric field, charged membranes can adsorb multiple layers of proteins, which exceed the capacity limit of common resins or membranes. It enlarges sample loading and trapping efficiency, thus bypasses the tradeoff between sample capacity and downstream detection sensitivity. This integrated approach, formed by synergistic utilization among electric field, membrane, and fluidic handling at the microscale, reduces the overall complexity of crude samples in one step for direct MS analysis. The sample preparation goals, including enrichment, desalting, removal of noncharged contaminants, and initial fractionation, can be rapidly performed in a single device. The strategy facilitates reproducible MS quantification by circumventing traditional laborious and time-consuming sample preparation steps. In addition, MEPD extended the ion trap linear dynamic range from 2 to at least 4 orders of magnitude by eliminating ion suppression effect, enriching target analyte(s), and decreasing sample loss during integrated sample preparation.

Quercetin greatly enhanced luminol electrochemiluminescence of quercetin in alkaline solution. When the concentration of luminol was 0.1 mol L−1, the detection limit for quercetin was 2.0 × 10−8 mol L−1 with a linear range from 1.0 × 10−7 to 2 × 10−5 mol L−1. The pH and buffer substantially affected ECL intensity. Quercetin was autoxidized in alkaline aqueous solution. The rate of autoxidation of quercetin in various pH buffers and borate concentrations were measured. Borate was found to inhibit quercetin autoxidation and compromise quercetin enhancement effect on luminol ECL to some extent. Two final autoxidation products were identified with LC–MS methods. Autoxidation process was associated with enhancement of ECL intensity. The ROS generated during quercetin autoxidation enhanced the ECL intensity.

In this study, an online concentration method in micellar electrokinetic chromatography (MEKC) applying field-enhanced sample injection (FESI) mode was developed for the detection of aristolochic acids (AAs) in Chinese medicine preparations. AA-I and AA-II were baseline separated with high separation efficiency, and 100-fold enhancement of the detection sensitivity was achieved compared with those obtained from normal capillary zone electrophoresis (CZE) or simple MEKC method. The proposed method was successfully applied for the determination of AAs in Chinese medicine preparations.

Chitosan and its derivatives have been widely used in many fields for their various function, there were some difference in bioactivities and applications between them. In this paper, a direct capillary zone electrophoresis (CZE) method without any pre-treatment was developed for separation of chitosan and its derivative, a water soluble chitosan called carboxymethyl chitosan (CM-chitosan), which was proved to be rapid and effective with satisfactory resolution. Optimization of conditions including pH, concentration of the buffer, and length of column were investigated, showing that when employing 50 mM sodium phosphate at pH 2.0 and untreated fused silica capillary, high-molecular weight chitosan and CM-chitosan were baseline separated with ultraviolet (UV) detector with satisfactory repeatability and excellent linear responses. Therefore, this method could be applied to separate and identify chitosan and CM-chitosan in biological samples and commercial products.

In this study, the separation of 13 homologous stick-like hydrophobic solutes, i.e., biphenyl nitrile derivatives, by organic-solvent-based micellar electrokinetic chromatography (MEKC) was investigated in terms of separation medium composition, species and concentration of surfactant, other additives, separation voltage and temperature. The results showed that the 13 strong hydrophobic compounds were baseline separated in 25 min with a repeatability of less than 1.3% (RSD) for migration time. The separation medium was a mixture of methanol, 2-propanol and water (58.5:10:31.5), containing 150 mM cetyltrimethylammonium bromide (CTAB) and 20 mM sodium borate. Variety of solvent composition, temperature and applied voltage all showed remarkable effect on the separation. The organic-solvent-based MEKC method proved to be superior to the aqueous MEKC and microemulsion electrokinetic chromatography (MEEKC) methods for the separation of strongly hydrophobic compounds.

Two insecticides, diflubenzuron and hexaflumuron, and their analogs have been separated by liquid chromatography (LC) and their fragmentation mechanisms were studied by electrospray ionization-ion trap mass spectrometry (ESI-MSn) in both positive- and negative-ion modes. Sequential product ion fragmentation experiments were performed in order to explain the degradation pathways and identify their predominant fragment ions. It was indicated that the characteristic fragmentations are the loss of neutral molecules such as HF, HNO2, and HCl to form stable ring structure or the cleavage of the acyl amine to form conjugated structure. Furthermore, the separation and determination of two benzoylurea (BU) insecticides and their analogs in the water samples from Weiming Lake have been described by LC–ESI-MS in negative mode. By the use of deprotonated molecule for quantitative analysis at low capillary exit voltage, low detection limits, good linearity and reproducibility for standard solutions were presented.

Phytohormones are key regulators in various physiological processes of plant growth and development. To better understand their regulatory actions, fast, sensitive and accurate methods for phytohormone analysis are critically required, and great efforts have been invested in this field. In this review, recent advances and developments in phytohormone determination strategies are presented, in terms of sample preparation and analytical approaches. Many types of analytical techniques are involved, including chromatography, mass spectrometry, immunoassay and others. Some challenges and prospects are also discussed.

ZnSn(OH)6 and binary-component SnO2–ZnSn(OH)6 were introduced as affinity probes for phosphopeptide enrichment for the first time. Two strategies, either ZnSn(OH)6 and SnO2 serial enrichment or binary-component SnO2–ZnSn(OH)6 enrichment in a single run, were proposed to enhance multi-phosphopeptide enrichment and to significantly improve global phosphopeptide detection.

Magnetic functionalized homochiral metal–organic frameworks (MOFs) were prepared and applied to efficient enantioselective fishing of chiral drug intermediates. Under optimized conditions, the enantiomeric excess (ee) value as high as 85.2% was achieved for methyl phenyl sulfoxide (MPS) within 3 min.

A polymer monolith microextraction (PMME) procedure coupled to plasma assisted laser desorption ionization mass spectrometry (PMME-PALDI-MS) was developed for rapid and organic solvent-free trace analysis. The extraction device used a “Dip-it” sampler coated with a MWNT incorporated monolith, and the analytes adsorbed on monoliths were effectively desorbed by laser, improving detection sensitivity.

A lithium-rich composite metal oxide was evaluated as a novel matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). The low background interference and lithium-rich feature made it a highly efficient matrix for the analysis of small molecules with high reproducibility, sensitivity and strong salt tolerance.