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We present an approach for the elucidation of C=C bond position and cis/trans isomers, which is achieved by the reaction of ambient water radical cations and double bonds, followed by the fragmentation of epoxide radical cations to generate diagnostic ions in tandem mass spectrometry. Hexenol double bond positional isomers and cis/trans isomers which exhibit different properties and biological functions are characterized as a proof of concept. The merits of the approach include the simplicity of experimental setup, rapid derivatization (within seconds), the obviation of organic solvents, as well as easy spectral interpretation.

Tissue samples are widely used for the study of metabolomics, lipidomics and proteomics due to their abundant useful biomolecular information. Modern analytical mass spectrometry has the ability to directly obtain the molecular information contained in various tissue samples (e.g., plant tissues, animal tissues, and clinical tissues, etc.) in real-time, with minimal or no sample pretreatment. Such features of analytical mass spectrometry promote the throughput of tissue analysis and extend the application of tissue analysis in multiple fields. This review summarizes the applications of mass spectrometry in direct analysis of plant tissues, animal tissues and clinical tissues, and the challenges and perspectives of mass spectrometry in direct analysis of tissue samples are discussed as well.

The deployment of mini mass spectrometers on the field strongly demands efficient ionization sources that are easy-to-operate. Nano-electrospray (nESI) ion source has been widely used in the field of chemistry, biology, medicine, pharmaceutical industry, clinical assessment and forensic science. In this study, a high ohmic resistor hyphenated gel loading tip nESI source was coupled with our home developed mini mass spectrometer. This ionization source has the advantages of simple-in-design, disposable and low-in-cost, therefore it could be frequently used for analysis of aqueous samples without leading to cross contamination. Performances of the gel loading tip nESI emitter were similar to pulled glass capillary, and highly compatible for the analysis of biomolecule in aqueous solution. Different peptide and small molecules have been confirmed with a continuous atmospheric pressure-interfaced (CAPI) mini mass spectrometer. The corona discharge, which was usually observed at nESI emitter tip under high aqueous solvent conditions, resulting in low ion intensity, has been successfully quenched using a 10 GΩ resistor in both a pulled glass capillary and a gel loading tip as nESI emitter in this study. Compared with conventional ESI, the metal wire assisted gel loading tip facilitated loading and direct analysis of biological samples without sample pretreatment.

In this paper, a BiVO4/FeVO4 heterostructure photoanode was synthesized by electrospray technique, and its photoelectrochemical water oxidation performance was investigated. The maximum photocurrent density of 0.4 mA cm−2 at 1.23 VRHE was 6 times higher than that of pristine BiVO4 films (0.06 mA cm−2). Through the analysis of the electrochemical impedance spectroscopy (EIS) results, the improvement of photoelectrochemical performance could be attributed to the formation of heterostructure at the two-phase interface, which led to the effective separation of electron-hole pairs. This work offers a new effective strategy to construct semiconductor nanocomposites for efficient photoelectrochemical water oxidation.

Endometriosis is a recurrent and benign gynecological disorder, defined by the ectopic presence of endometrium. About 10% of reproductive-aged women suffer from endometriosis. There are no non-invasive or minimally invasive tests available in clinical practice to accurately diagnose endometriosis today. Here, we present our efforts to determine the diagnostic accuracy of biomarkers in peritoneal fluid and blood plasma using flow injection analysis with electrospray ionization tandem mass spectrometry (ESI-MS/MS) in 70 women with endometriosis and 20 women from a control group. The presence of endometriosis was confirmed by surgical findings and post-operative pathological examination. A qualitative and quantitative evaluation of the lipids in peritoneal fluids and blood plasma was carried out using electrospray ionization mass spectrometry (ESI-MS). The analysis revealed more than 140 molecular species of lipids, most of which pertained to five classes: phosphatidylcholines, phosphatidylethanolamines, sphingomyelins, di- and triglycerides. The data were analyzed using a statistical multifactorial method (i.e., PLS-DA). It was found that 9 potential biomarkers of endometriosis (LPC 16:0, PE O-20:0, PE O 34:1, PC 36:2, PC 36:4, PC 36:5, PC 38:4, PC 38:6 and SM 34:1) are common in blood plasma and peritoneal fluid, supporting connection with the pathological process. The sensitivity of the method developed for plasma was 93% with a specificity of 95%; for peritoneal fluid, the sensitivity was 90% and the specificity 95%. Accordingly, plasma is the most suitable biological fluid for clinical diagnostics of endometriosis. Further validation of these lipids as serologic biomarkers may enhance non-invasive diagnostic tools for patients with suspected endometriosis and reduce the frequency of diagnostic laparoscopy.

This work depicts the synthesis of controllable Pd nanoparticles decorated TiO2 nanowire arrays by electrospray technique. By varying the substrate temperature and volume of precursor solution, Pd/TiO2 hybrid structure with different sizes and deposition yield was precisely controlled. The highest photocurrent density of the Pd/TiO2 photoanode was 1.4 mA cm−2 at 1.23 V vs. RHE, which was approximately 5 times higher than the pristine TiO2. The onset potential with a significant cathodic shift of 80 mV compared to the pristine TiO2 was also observed. To the best of our knowledge, the obtained photocurrent showed the optimal photocurrent density and high stability compared with previous reports. It is also found that the photoelectrochemical performance is closely related to the size and deposition quantity of Pd nanoparticles. According to the results, the enhanced PEC performance can be attributed to the Schottky junction, charge transfer and the enhancement about the separation efficiency of the photogenerated electrons and holes betweenTiO2 and Pd NPs. This result demonstrated that this method may design a new and green strategy for synthesizing the well-defined morphologies, compositions, and sizes of the hybrid nanomaterial for photocatalytic hydrogen generation, photocatalytic CO2 reduction and photosynthesis of organic molecules.

Pyroptosis is a form of programmed necrosis, and is morphologically and mechanistically unique form of programmed cell death compared to others, such as apoptosis and autophagic cell death. More specifically, pyroptosis features gasdermin family-mediated membrane pore formation and subsequent cell lysis, as well as release of pro-inflammatory intracellular contents including IL-1β, IL-18 and HMGB1. Mechanistically, pyroptosis is driven by two main signaling pathways - one mediated by caspase-1 and the other by caspase-4/5/11. Recent studies show that pyroptosis is implicated in several cardiovascular diseases. In this review, we summarize recent scientific discoveries of pyroptosis's involvement in atherosclerosis, myocardial infarction, diabetic cardiomyopathy, reperfusion injury and myocarditis. We also organized new and emerging evidence suggesting that pyroptosis signaling pathways may be potential therapeutic targets in cardiovascular diseases.

Number sense is the spontaneous ability of human adults, infants, newborns, and other animals to process approximate numbers. However, how number sense can emerge in the absence of learning and fine-tuning has not been elucidated. On the basis of the treatment of visual pathways as an information processor, we developed two computational models for numerosity detection with single and dual suppression values. The information processor transforms the visual information of numerosities into input information of neurons in the parietal and prefrontal cortex via suppression and visuotopic mapping without the need for the construction of neural networks, training, and fine-tuning. In the single suppression model, the suppression width is a more fundamental determinant than numerical quantity in numerosity detection. Our dual suppression model clarifies the effect of suppression width values in two visual regions on spontaneous numerosity detection. It also predicts innate and acquired training behavior in humans and animals. Results suggest that the range of the lateral inhibition of neurons at successive stages in visual pathways is the neural basis of human number sense that ultimately gives rise to number theory and mathematics.

Over the past decade, ambient mass spectrometry (AMS) has become an important scientific research tool which has been widely used in various important fields such as pharmaceuticals, food, environment, public safety, clinic diagnosis and so on. Ambient ionization technology, as the key for AMS analysis, allows the direct sampling/ionization of analytes from raw practical samples without any sample pretreatment, and has greatly improved the analytical efficiency. At present, nearly 100 of different ambient ionization technologies have been developed for the study of complex solid, gaseous, liquid, and even viscous samples. Herein, the ambient ionization methods were introduced in the aspect of energy and charge transfer process, and the new ambient ionization devices developed in the recent 5 years were briefly summarized and discussed. Furthermore, the advantages and disadvantages of the ambient ionization technology and the possible development direction of atmospheric ionization technology in the future were prospected.

Ambient mass spectrometry (AMS) allows direct molecular characterization of various raw food samples with minimal or no sample pretreatment. Because of the excellent sensitivity and specificity of analysis, AMS has been increasingly applied in food science and industry. In virtually, any type of food samples including solid, liquid, viscous, and bulk food samples could be directly analyzed using mass spectrometry powered by versatile ambient ionization techniques. Moreover, mass spectrometry imaging (MSI) offers a unique opportunity to explore the spatial-chemical information from numerous food samples. Herein, the principle of AMS, typical instrumental setup, and applications in different type of food samples are systematically reviewed, the advantages and shortages of AMS for food analysis are mentioned, and the impact and challenge of AMS on food science are briefly discussed.

Electrical conductivity between substrate and catalyst is a key factor restricting the OER (oxygen evolution reaction) catalytic activity of transition metal oxides. Herein we report a facile and direct route for synthesizing spinel NiCo2O4 nanostructure on conductive substrates by electrospray technique. By simply altering the substrate temperature, film thickness and voltage, NiCo2O4 with different morphology and electrocatalytic performance was obtained. The optimal performance showed a low overpotential of 375 mV at 10 mA/cm2 and an excellent stability over 15 h. This work proved that electrospray technology is an effective strategy to fabricate the binder-free catalysts with high activity and stability for OER.

Study Objective To introduce a method for the rapid assessment of endometriotic tissues using direct mass spectrometry (MS)-based lipidomics. Design A prospective observational cohort study (Canadian Task Force classification II2). Setting Department of Operative Gynecology of the Research Centre for Obstetrics, Gynecology and Perinatology. Patients Fifty patients with ovarian cysts and peritoneal endometriosis who underwent laparoscopic surgery between 2014 and 2016. Intervention Differences in mass spectrometric profiles of ectopic endometria (endometriosis) and eutopic endometria were analyzed for each patient in combination with morphohistologic evaluation. The lipidomic approach was applied using a direct high-resolution MS method. Measurements and Main Results Of 148 metabolites, 15 showed significant differences between endometriotic tissue and a healthy endometrium of the same patient, considered as a control in this study. The main lipids prevalent in endometriotic tissues were phosphoethanolamine (PE O-20:0), sphingomyelin (SM 34:1), diglycerides (DG 44:9), phosphatidylcholines (PC 32:1, PC O-36:3, PC 38:7, PC 38:6, PC 40:8, PC 40:7, PC 40:6, PC 40:9, and PC O-42:1), and triglycerides (TG 41:2, TG 49:4, and TG 52:3). Using partial least squares discriminant analysis models, MS showed that the lipidomic profile of endometriotic tissue (peritoneal endometriosis and ovarian endometriomas) was clearly separated from the eutopic endometrium, indicating tissue-type differentiation. Conclusion Our results suggest that direct MS may play an important role for endometriotic tissue identification. Such an approach has potential usefulness for real-time tissue determination and differentiation during surgical treatment. Lipids of 3 important classes, sphingolipids, phospholipids, and the fatty acids (di- and triglycerides), were identified. Validation is required to determine whether these lipids can be used to discriminate between patients with endometriosis and those with other gynecologic diseases.

The chemical origin and biological role of distinct semen-like odor occasionally found in some flowers are very curious but remain scarcely studied. Here, we used direct ambient corona discharge ionization mass spectrometry (MS) to study the volatile chemical composition behind the semen-like odor emitted by the fresh flowers of Photinia serrulata, Castanopsis sclerophylla and Stemona japonica without any chemical pretreatment. Chemical identification was performed using high-resolution MS analysis in combination with tandem MS analysis and whenever possible was confirmed by the analysis of standard reference compounds. A total of 19 compounds, mostly belonging to nitrogenous volatiles, were identified in P. serrulata, C. sclerophylla, and S. japonica flowers, 1-pyrroline, 1-piperideine, 2-pyrrolidone, and phenethylamine being common in all the three studied species. Several lines of evidence indicate that the major component responsible for the semen-like odor is most likely 1-pyrroline. 1-Pyrroline is most probably formed via the oxidative deamination of putrescine, as indicated by the observation of signal from 4-amino-butanal intermediate. Flower visitation observations suggest that the released volatiles serve to attract dipterans, including Syrphidae, Calliphoridae, and Muscidae. On the analytical side, the comparison of our results to earlier studies also indicate that compared to the traditional GC-MS approach the direct corona discharge ionization mass spectrometry provides more sensitive detection of VOCs with high proton affinity, in particular volatile amines, and therefore can be used to complement traditional GC-MS approach for the highest chemical coverage of VOC analysis.

As an important part of the power system, power load forecasting directly affects the national economy. Small improvements in power load forecasts can save millions of dollars for the power industry. Therefore, improving the accuracy of power load forecasting has always been the pursuing goal for a power system. Based on this goal, this paper proposes a novel connection, the dense average connection, in which the outputs of all preceding layers are averaged as the input of the next layer in a feed-forward fashion. Dense average connection can alleviate the problem of gradient explosion without introducing new parameters. Based on dense average connection, we construct the dense average network (DaNet) for power load forecasting. On two public datasets (ISO-NE dataset and NAU dataset), we use MAPE, MAE and RMSE to evaluate the performance of DaNet. The predictions of DaNet are better than those of existing benchmarks. On this basis, this paper uses the ensemble method to reduce the peak value of prediction bias, which helps to alleviate the dispatching problem caused by unexpected loads. To verify the reliability of the model predictions, the robustness is analyzed and verified by adding input disturbances. The experimental results show that the proposed model is effective and robust for power load forecasting.

Rapid mass spectrometry analysis of protein in liquid sample was carried out by using a charged bubble extractive ionization device. In this work, experimental parameters including gases (N2 and CO2), bubble path length, voltage, and gas pressure on the charged bubble extractive ionization of lysozyme were investigated. Under the optimum experimental parameters including CO2 as extraction gas, bubble path length of 32 cm, solution voltage of 2 kV, and gas pressure of 0.05 MPa, lysozyme in liquid sample were successfully detected with the limits of detection of 1 × 10−8 M in aqueous solution and 1 × 10−7 M in diluted urine (200 times with ultrapure water), respectively. In addition, the limit of detection of 1 × 10−5 M was obtained for undiluted urine sample. By comparing the desalting effects of charged bubble extractive ionization mass spectrometry with ESI-MS, it was found that the charged bubble extractive ionization method could obtain a wider and lower charge state distribution of protein ions, and showed higher tolerance facing non-volatile inorganic salts. Off-line study of the collected catalase after charged bubble extractive ionization showed that 53.9% enzyme activity was remained, which indicated that the proposed method was a soft ionization method. The method had merits including no sample pretreatment, no chemical reagent contamination and high speed, showing potential application to mass spectrometry analysis of protein components in solution samples.

A growing number of studies investigating the association between Single Nucleotide Polymorphisms (SNPs) and lung cancer risk have been published since over a decade ago. An updated integrative assessment on the credibility and strength of the associations is required. We searched PubMed, Medline, and Web of Science on or before August 29th, 2016. A total of 198 articles were deemed eligible for inclusion, which addressed the associations between 108 variants and lung cancer. Among the 108 variants, 63 were reported to be significantly associated with lung cancer while the remaining 45 were reported non-significant. Further evaluation integrating the Venice Criteria and false-positive report probability (FPRP) was performed to determine the strength of cumulative epidemiological evidence for the 63 significant associations. As a result, 15 SNPs on or near 12 genes and one miRNA with strong evidence of association with lung cancer risk were identified, including TERT (rs2736098), CHRNA3 (rs1051730), AGPHD1 (rs8034191), CLPTM1L (rs401681 and rs402710), BAT3 (rs3117582), TRNAA (rs4324798), ERCC2 (Lys751Gln), miR-146a2 (rs2910164), CYP1B1 (Arg48Gly), GSTM1 (null/present), SOD2 (C47T), IL-10 (-592C/A and -819C/T), and TP53 (intron 6). 19 SNPs were given moderate rating and 17 SNPs were rated as having weak evidence. In addition, all of the 29 SNPs identified in 12 genome-wide association studies (GWAS) were proved to be noteworthy based on FPRP value. This review summarizes and evaluates the cumulative evidence of genetic polymorphisms and lung cancer risk, which can serve as a general and useful reference for further genetic studies.

Salbutamol and clenbuterol as β-agonists are illegally added in pig feed, resulting in pork contaminated and even leading excessive excitability of athletes. Therefore, it has a great significance for establishing a new rapid detection method of salbutamol and clenbuterol in pork. In this study, internal extraction electrospray ionization mass spectrometry (iEESI-MS) technique was used for directly qualitative and quantitative analysis of salbutamol and clenbuterol in pork tissues without any sample pretreatment. The results showed that this method had a high sensitivity to salbutamol and clenbuterol analysis with detection limits of (LOD) 6.2 and 9.8 ng kg−1, respectively, while the analysis time for detecting single sample and single index was less than 30 s. In a range of 0.01–1000 μg kg−1, the logarithm of signal intensity (Y) and the logarithm of concentration (X) had a good linear relationship. This method had many advantages such as rapid analysis, low sample consumption and high sensitivity, which was ideal for the rapid detection of trace salbutamol and clenbuterol.

Phospholipids and their metabolites play an important role in a variety of cellular processes including cell-cell adhesion, cell growth and differentiation, apoptosis, phagocytosis as well as storage of energy. In this study, the phospholipid composition of cancer tissue and adjacent normal tissue from humans and animals were analyzed by internal extractive electrospray ionization mass spectrometry (iEESI-MS). Extractive solvent at high voltage (+5.5 kV) was injected into tissue samples using a fused silica capillary at a flow rate of 0.5–1.0 μL min−1, producing fine charged droplets containing analytes of tissue samples at the tip of the sample. Charged droplets were directly sampled to the atmospheric inlet of a mass spectrometer. Out of 21 different ratios of CH3OH-H2O solvent mixture, the ratio CH3OH-H2O (30:70, V/V) showed the optimal phospholipids extraction and visibility in MS. A large number of phospholipids from different tissue samples (such as cancer tissue and adjacent normal tissue of lung cancer, esophageal tissue, pork, beef, porcine heart and porcine lung) were obtained simultaneously by iEESI-MS analysis. The experimental results demonstrated that iEESI-MS was characterized by minimal sample pretreatment, low sample consumption, and rapid analysis (the analysis time per sample was less than 1 min), and the selectivity and sensitivity of iEESI-MS could be improved by choosing proper solvent. Importantly, the experimental results provided new information for further studies of phospholipids in biological tissues.

Analyzing the chemical composition of nectar and honey will contribute to honey traceability, which has become a research hotspot in recent years. However, the rapid, green, and facile analytical methods without tedious chemical pretreatment remain to be developed. Herein, the extractive electrospray ionization high resolution-mass spectrometry (EESI-HRMS) was used to analyze the polyphenols and amino acids composition of the nectars and honeys from three Citrus species, and high-performance liquid chromatography coupled to ultraviolet detector (HPLC-UV) was used to validate the results. 12 polyphenols and 8 amino acids were identified by EESI-HRMS, whilst 9 polyphenols were quantified by HPLC-UV. Principal component analysis (PCA) revealed that the chemical composition of Citrus nectars was similar, and so do honeys, but the nectar and its corresponding honey were chemically differentiated. Accordingly, EESI-HRMS is a reliable analytical method for the analysis of samples with limited sources and complex composition, which contributes to the honey traceability.

Quantitative detection of phospholipids at the single cell level remains in challenge. Herein, the TiO2-coated Fe3O4 nanoparticles were synthesized to selectively enrich trace phospholipids from single cell, which were then eluted using 1.5% ammonia/methanol (w/w) for sensitive detection by electrospray ionization mass spectrometry. Under the optimal experimental conditions, eighteen phospholipids in single cell samples were detected and identified by MS/MS experiments. The limit-of-detections (LODs) were 0.012 μg/L for phosphatidylcholine (PC, 34:1) and 0.014 μg/L for phosphatidylcholine (PC, 36:2) in PBS matrix, with the linear range of 0.05–50 μg/L (R2 ≥ 0.999). The recovery rates of 94.90–104.00% were obtained, with the relative standard deviations (RSDs ≤ 6.90%). Quantitative determination of PC in real unicellular samples was also achieved, with the concentration of 1.82–2.11 μg/L for PC(34:1) and 1.25–1.65 μg/L for PC(36:2) in six types of single cell, opening up possibilities for quantitative analysis of trace compounds in complex bio-samples. A set of 6 types of tumor cells were analyzed and further differentiated by the partial least squares-discriminant analysis (PLS-DA). Conclusively, a facile method for the direct quantification of phospholipids in single cell samples has been developed, showing potential applications for advanced investigation of phosphorylated substance at the single cell level.

The internal extractive electrospray ionization mass spectrometry (iEESI-MS) has been applied to direct molecular analysis of garlic tissues. An extraction solvent (e.g., methanol) under a high voltage (+4.5 kV) was injected into the fused silicon capillary whose far end penetrated into the bulk tissue sample. The chemicals in the bulk tissue were selectively extracted by the working solvent and carried along the electric field toward the apex of the sample, to generate electrospray in front of an ion trap mass spectrometer. Without time-consuming sample pretreatment, active garlic substances such as organosulfur compounds (e.g., alliin, allicin), amino acids (e.g., arginine) and saccharides (glucose, polysaccharides) were successfully detected and directly identified via collision-induced dissociation (CID) in positive ion detection mode. Mass spectral fingerprints of different kinds of garlic cloves (24 samples), as well as various post-treated ones (36 samples) in the range of m/z 50–2000 Da, were classified via principal component analysis (PCA). The experimental results indicated that iEESI-MS allowed direct identification of chemical components in garlic tissue and rapid recognition of metabolic changes in the garlic tissue subjected to various external stimuli, with the analytical advantages such as simplicity, rapidity (less than 2 min per sample), good specificity, and minimal disturbance to the bioactivity of analytes.

To address the widespread contamination of surface soil by phthalate esters (PAEs), a method based on the surface desorption atmospheric pressure chemical ionization tandem mass spectrometry (SDAPCI-MS n ) imaging technology was successfully applied for the direct determination of diethyl phthalate (DEP) in soil without any pretreatment. The precursor ion, protonated diethyl phthalate ( m/z 223), was confirmed by collision-induced dissociation (CID) experiments to exclude false-positive results. The protonated DEP ( m/z 223) and the characteristic fragment ( m/z 177) were used to obtain the distribution of DEP molecules in the soil using imaging mass spectrometry. The two ion images without any pretreatment showed that the distribution of DEP was inhomogeneous in the shape of clusters, but these two distributions were changed after adding deionized water evenly into the surface of soil. The spatial resolution and the analysis speed per pixel were 0.25 mm 2 and 4.5 s. This new method may be applicable for the study of content and distribution of PAEs in other complex solid samples.

Sensitive detection of tetrabromobisphenol A (TBBPA) and its derivatives, a group of emerging toxic contaminants, is highly necessitated in environmental investigation. Herein a novel analytical strategy based on reactive extractive electrospray ionization (EESI) tandem mass spectrometry for detection of tetrabromobisphenol A bis(2-hydroxyethyl ether) (TBBPA-BHEE), tetrabromobisphenol A bis(glycidyl ether) (TBBPA-BGE), tetrabromobisphenol A bis(allylether) (TBBPA-BAE), and tetrabromobisphenol S bis(allylether) (TBBPS-BAE) in industrial waste water samples was developed. Active silver cations (Ag(+)), generated by electrospraying a silver nitrate methanol solution (10 mg L(-1)), collides the neutral TBBPA derivatives molecules in the EESI source to form [M+Ag](+) complexes of the analytes under the ambient conditions. Upon collision-induced dissociation (CID), characteristic fragments of the [M+Ag](+) complexes were identified for confident and sensitive detection of the four TBBPA derivatives. Under the optimized experimental conditions, the instrumental limits of detection (LODs) of TBBPA-BHEE, TBBPA-BGE, TBBPA-BAE and TBBPS-BAE were 0.37, 0.050, 0.76, and 4.6 μg L(-1), respectively. The linear ranges extended to 1000 μg L(-1) (R(2)≥0.9919), and the relative standard deviations (RSDs), inter-day variation and intra-day variation were less than 7.8% (n=9), 10.0% (n=5), and 14.8% (n=1 per day for 5 days) for all derivatives. TBBPA derivative manufacturing industrial waste water, river water and tap water samples were fast analyzed with the proposed method. The contents of TBBPA derivatives were various in the collected samples, with the highest 19.9±0.3 μg L(-1) of TBBPA-BAE in the waste water samples.

The fast, sensitive detection for 6 aromatic amines and direct observation of intermediates of Schiff-base reactions were achieved through reactive desorption electrospray ionization mass spectrometry (reactive DESI-MS). Pure acetone was electrosprayed to impact the aromatic amines on the paper, allowing two reactions, a proton-transfer reaction and a Schiff-base reaction, to occur in these experiments. The former was used to detect the aromatic amines, and the protonated analytes generated were selected for the qualitative and quantitative analysis. The false-positive signals were excluded by tandem mass spectrometry. For the 6 analytes, linear signal responses were obtained, and each had a dynamic range of 5 orders of magnitude. The relative standard deviation (RSD) and limit of detection (LOD) for all the measurements were in 1.5–5.3% and 0.03–0.2 pg/mm2 range, respectively. The latter is a nucleophilic addition reaction that occurred between the aromatic amines and the acetone. The carbinolamine intermediates of these reactions were directly detected and identified by reactive DESI-MS. The data show that reactive DESI-MS is not only a reliable, sensitive tool for chemical analysis, but also a valid and promising method for studying organic reactions simultaneously, especially for heterogeneous reactions that occurred at a solution/solid interface.

It is highly desirable to develop and validate novel methods for detecting cancer with higher sensitivity and better specificity. The aim of this review is to introduce a relatively new approach, metabolomics, and explore its potential for cancer diagnosis. We briefly introduced the concept of metabolomics and its relationship with other omics studies in systems biology for cancer detection. The field of metabolomics focuses on the parallel measurement of hundreds of small molecule metabolites in biological samples such as blood, urine, and biopsied tissue. Since metabolite levels are sensitive to subtle changes in the pathological status, metabolomics promises novel avenues for early cancer detection and a better understanding of cancer processes. In fact, many previous metabolomics studies have demonstrated the promises of metabolomics not only for the diagnosis of various kinds of cancer, but also for therapeutic monitoring as well as for drug development. In addition, in this review we discussed the challenges and future directions for developing metabolomics methods towards clinical applications for cancer diagnosis.

A sensitive approach, based on semi-quantitative measurement of the characteristic fragments in multistage extractive electrospray ionization mass spectrometry (EESI-MSn), was developed for fast detection of trace levels of lead in aqueous liquids including mineral water, lake water, tap water, energy drinks, soft drinks, beer, orange juice, and tea. A disodium ethylene-diamine-tetraacetic acid (EDTA) aqueous solution was electrosprayed to produce negatively charged primary ions which then intersected the neutral sample plume to generate anions of EDTA-Pb(II) complexes. The charged EDTA-Pb(II) complexes were characterized with multistage collision induced dissociation (CID) experiments. The limit of detection (LOD) using EESI-MS3 was estimated to be at the level of 10(-13) g/mL for directly detecting lead in many of these samples. The linear dynamic range was higher than 2 orders of magnitude. A single sample analysis could be completed within 2 min with reasonable semi-quantitative performance, e.g., relative standard deviations (RSDs) for deionized water were 4.6-7.6% during 5 experimental runs (each of them had 10 repeated measurements). Coca-cola and Huiyuan orange juice, representative beverage samples with complex matrices, generated recovery rates of 91.5% and 129%, respectively. Our experimental data demonstrated that EESI-MS is a useful tool for the fast detection of lead in various solutions, and EESI-MS showed promises for fast screening of lead-contaminated aqueous liquid samples. (C) 2012 Elsevier B.V. All rights reserved

High throughput analysis of sunscreen agents present in cream cosmetic has been demonstrated, typically 2 samples per minute, using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) without sample pretreatment. For the targeted compounds such as 4-Aminobenzoic acid and oxybenzone, ND-EESI-MS method provided linear signal responses in the range of 1-100 ppb. Limits of detection (LOD) of the method were estimated at sub-ppb levels for the analytes tested. Reasonable relative standard deviation (RSD=8.4-16.0%) was obtained as a result of 10 independent measurements for commercial cosmetics samples spiked with each individual sunscreen agents at 1-10 ppb. Acceptable recoveries were achieved in the range of 87-116% for direct analysis of commercial cream cosmetic samples. The experimental data demonstrate that ND-EESI-MS is a useful tool for high throughput screening of sunscreen agents in highly viscous cream cosmetic products, with the capability to obtain quantitative information of the analytes.

A thermal dissociation atmospheric chemical ionization (TDCI) source was developed for the rapid chemical ionization of ambient analytes in complex matrices. The performance of TDCI has been experimentally explored by coupling the TDCI source to a commercial LTQ XL mass spectrometer, and the dissociation of chemical reagents, for example ionic liquids, has been systematically investigated using multiple stage mass spectrometer. The primary ions, generated through the thermal dissociation process of the ionic liquids, were accelerated by the bias voltage applied to the repelling electrode of the TDCI source, then reacted with the analytes present in the matrices of the raw samples to produce analyte ions. The analyte ions were finally guided into the LTQ instrument for mass analysis. The construction of the TDCI source was detailed in the text. The effects of the experimental parameters such as the temperature, the distance, and the angles formed between the electrodes were experimentally studied using the signals of characteristic fragments of the ionic liquid. Under the optimal experimental conditions, TDCI was able to directly ionize a wide variety of compounds, including the poplar (e.g., amino acids, doping compounds) and nonpolar chemicals (e.g., naphthalene), for sensitive detection using LTQ-MS, without any sample pretreatment. The average time for a single sample analysis was less than 30 s, the relative standard deviation of the method was in the range of 5.89%–11.1%, and the limit of detection (LOD) for naphthalene was estimated to be 2.9 × 10 −7 g L −1 .

A rapid analytical method based on nanoliter-level sampling technique and surface desorption atmospheric pressure chemical ionization mass spectrometry (SDAPCI-MS) has been developed for the determination of trace dimethoate in juices without any sample preparation. The nanoliter-level juices were sampled by a home-made sampler equipped with a stainless steel sampling probe. The minimum sampling volume was suggested to be 0.11 nL. Based on the experimental results, the linear correlation between dimethoate signal and concentration was significant in the range of 0.001−10.0 mg kg −1 with the correlation coefficient ( R ) of 0.988. The recoveries were in the range of 80.5%–120.6%, and the detection limit of dimethoate was determined to be 1.2×10 −11 mg kg −1 .

The characteristic fragment (m/z 85) of protonated melamine, generated in MS/MS spectra recorded from the surface of egg slices using surface desorption atmospheric pressure chemical ionization mass spectrometry (SDAPCI-MS), has been used to image melamine in slices of cooked egg. The experimental results showed that the spatial resolution of the imaging using SDAPCI-MS was 0.06 mm2. Egg yolk was proven to have little melamine in this study, and the most melamine was contained in egg white region, although not evenly distributed.

Plastic materials that release free toluene-2,4-diisocyanate (TDI) can be commonly found in sports venues. As the presence of TDI in the atmosphere will result in severe air pollution, the WHO has enforced strict regulations to ensure that the proportion of the free TDI monomer in the isocyanate-polymer is lower than 0.5%. In this study, ambient air samples containing trace amounts of TDI-water aerosols were collected with glass syringes on the spot and then directly injected into a home-made extractive electrospray ionization (EESI) source. The EESI source was installed on a LTQ-MS instrument for the direct analysis of samples with complex matrices. The raw samples were directly analyzed by tandem EESI-MS without any sample pretreatment under the following working conditions: spray voltage, 3 kV; capillary voltage, 21 V; and capillary temperature, 175 °C. A single sample analysis, along with tandem MS experiments for enhanced specificity, was completed within 1 s. The limit of detection was found to be less than 0.04% ( n = 5, S/N = 100), considerably lower than that allowed in the air. The relative standard deviation of the analysis results was no higher than 1.4%.

By combining the advantages of desorption electrospray ionization (DESI) and atmospheric pressure chemical ionization (APCI), a novel ambient surface desorption atmospheric pressure chemical ionization (SDAPCI) source is developed for direct detection of trace amounts of analytes in various complex matrices without any sample pre-treatment. In the SDAPCI source, a self-assembled corona discharge was employed to generate the primary ions, which were directed to impact the sample surface to yield positive/negative ions of analytes for mass analysis. Using ambient air (about 45%–60% relative water moisture) as a reactive reagent for chemical ionization to generate primary ions such as H3O+ in positive ion detection mode or H2O·OH− in negative ion detection mode, SDAPCI allows mass spectrometric analysis of ambient samples without toxic contamination, and provides simplicity in its implementation for in-situ analysis in a miniature mass spectrometer. The principle and construction of an SDAPCI source are presented in this contribution. Successful detection of trace amounts of active ingredients of various pharmaceutical preparations was demonstrated using the homemade SDAPCI source with ambient air as the reactive reagent. Using pure argon gas instead of the ambient air, radical cations of acetaminophenol and peptide I–7 were successfully observed and structurally characterized by MS/MS experiments, which provided the experimental evidences for the production of radical cations of peptides at atmospheric pressure. The data show promising applications of SDAPCI-MS for direct analysis of ambient surfaces with neither sample pre-treatment nor toxic chemical contamination.