傅里叶变换-离子回旋共振质谱

本文介绍了傅里叶变换-离子回旋共振质谱(FT-ICRMS)的基本原理、发展历史、仪器特点。与其它类型质谱相比较,FT-ICRMS具有超高质谱分辨率、高质量测量准确度、回旋池内现场反应等显著优点,有望在多种学科的研究中得到更广泛的应用。     

An Electrospray Method Using a Multi‐Capillary Nozzle Emitter

A multi‐capillary nozzle emitter consisting of one metal plate with capillary nozzles and a ring type counter electrode was used as a multi‐electrospray atomizer. The number of capillary nozzles, flow rate of the liquid and the interval between the capillary nozzles were changed, and the droplet diameter and the voltage required for a steady cone‐jet mode were measured. For the multi‐capillary nozzle emitter, the interaction between the capillary nozzles is the important factor for obtaining fine droplets of uniform size. These fine droplets are obtained when there is only a small interaction between the capillary nozzles, and the equations obtained from the single capillary nozzle case are also applicable for the multi‐capillary nozzle emitter. When the number of capillary nozzles decreases (a situation which is not good for obtaining a large amount of droplets) or the interval between the capillary nozzles increases, the interaction between the capillary nozzles can be reduced. As the number of capillary nozzles increase, a higher voltage is required to obtain a fine droplet of uniform size.     

Brazilian cachaça: “Single shot” typification of fresh alembic and industrial samples via electrospray ionization mass spectrometry fingerprinting

Copper pot stills (alembics) and industrial stainless steel columns are the most common distillation devices used in Brazil to produce sugarcane spirit (cachaça). The use of both apparatus originates two distinctive products, the so-called (a) alembic (the most valuable) and (b) industrial cachaças, respectively, with subtle but characteristic chemical compositions and sensorial properties. Herein, we demonstrate that the use of direct infusion electrospray ionization mass spectrometry in the negative mode, ESI(−)–MS, is able to provide fast “single shot” fingerprinting discrimination between these two types of spirits. Representative samples of both spirits show ESI(−)–MS with regular sets of diagnostic ions of m/z 279, 255, 199, 171, 143 (alembic) and of m/z 377, 341 (industrial). Principal component analysis (PCA) of the ESI(−)–MS data consistently split the 34 alembic and the 14 industrial samples into two well-defined groups. Sugar addition to the alembic samples was also easily detected.     

Improved performance of organic photovoltaic cells with PTB7-Th:PC71 BM by optimized solvent evaporation time in electrospray deposition

As poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b; 4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] has good potential as a low-band gap donor polymer for organic photovoltaic cells (OPVs), we investigated the optimized electrospray deposition condition for realizing suitable polymer ordering and/or crystallite size by controlling the solvent evaporation time. Previous studies on the electrospray process have mainly focused on novel device structure owing to its unique characteristic of small droplet size, which is less than 1 μm. However, in this research, we investigated the spontaneous formation of interpenetrating continuous networks of the donor- and acceptor-rich domains of solvent evaporation during the electrospray process. By evaluating the ultraviolet–visible absorption spectrum, Raman spectroscopy, and direction of polymer ordering, it was shown that the polymer-stacking condition was not influenced by solvent evaporation time, even though poly(3-hexylthiophene-2,5-diyl) along the face-on direction was well stacked under the slow solvent evaporation condition. In contrast, the crystallite size, which was estimated from the full width at half maximum X-ray diffraction pattern, increased as the solvent evaporation time increased. This means that the crystalline grain spontaneously grew in the droplet and that the large crystalline grain was formed during the slow evaporation condition. Furthermore, the photovoltaic performance trend was the same as the performance trend of the crystallite size and were increased with increasing solvent evaporation time for both polymers. Therefore, the crystalline grain size was a dominant factor in determining the photovoltaic performance. Additionally, the crystalline grain size could be controlled by the solvent evaporation time. Finally, by optimizing the active-layer thickness, the highest photoconversion efficiency of 8.6% was achieved. This is the highest value of an electrospray-based device. These results indicate that the solvent evaporation time is an important factor in determining the crystallite size of an organic thin film, which directly affects the photoconversion efficiency of OPVs.     

Facile preparation of BiVO4/FeVO4 heterostructure for efficient water-splitting applications

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 V_RHE 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.     

Electrodes based on nafion and epoxy-graphene composites for improving the performance and durability of open cathode fuel cells,prepared by electrospray deposition

Fabrication of electrodes for polymer electrolyte fuel cells is a intriguing process in which a balance between gas transport, electrical conductivity, proton transport and water managing must be optimized. In this work four different electrodes prepared by electrospray deposition have been studied using different catalytic inks, in which Nafion and epoxy doped with Graphene-Nanoplatelets were used as binders. After studying the behavior of those electrodes in a single open cathode fuel cell proton electrolyte membrane, it is clear that the addition of epoxy as binder doped with graphene, improves the performance of the fuel cell and increase the mechanical stability of the electrode avoiding the loose of catalyst during the electrode manipulation in the fuel cell assembly process and the durability of the fuel cell. To explain this behavior, an ex-situ study was carried out, in which properties such as its surface morphology, hydrophobicity and electrical and thermal conductivity of those electrodes were studied. From the results of this study, such improvement in the performance of the fuel cell was justified on the basis of the increase in the electrical conductivity, a diminution in its thermal conductivity and an enhancement of hydrophobicity (surface morphology) of the deposited catalyst layer, when an optimum quantity of epoxy is added to the catalytic ink that makes to improve the mechanical properties of those electrodes.     

Simulation and parametric study of a novel multi-spray emitter for ESI–MS applications

In this work, we propose a novel carbon nanofiber (CNF) emitter for electrospray ionization (ESI)–mass spectrometry (MS) applications. The proposed emitter comprises an array of CNFs around the orifice of a microscale capillary. The electrospray ionization process is simulated using a CFD code based on Taylor–Melcher leaky-dielectric formulations for solving the electrohydrodynamics and volume-of-fluid (VOF) method for tracking the interface. The code is validated for a conventional multiple electrospray emitter and then applied to simulate the CNF emitter model. The modeling results show that under steady state condition, individual cone-jets are established around each of the CNFs resulting in an array of electrosprays. The approach being taken to fabricate the CNF emitter is briefly discussed. Effects of geometrical parameters including aspect ratio of CNFs, total number of CNFs and distribution pattern of the CNFs on the electrospray performance are studied. The influence of operating parameters such as flow rate, potential difference and physical properties of the solvent on the electrospray behavior is thoroughly investigated. The spray current, ‘onset’ potential and jet diameter are correlated with total number and distribution of CNFs and physical properties of the liquid. The correlation results are compared with the available results in the literature. Higher spray current and lower jet diameter indicate that the device can perform equivalent to nanospray emitters while using a micro-scale orifice. This allows higher sample throughput and eliminates potential clogging problem inherent in nano-capillaries.     

Azaspiracid shellfish poisoning: unusual toxin dynamics in shellfish and the increased risk of acute human intoxications

A number of recent acute human intoxications in Europe from the consumption of Irish mussels have been attributed to the presence of a new class of toxins named azaspiracids. The study demonstrates that azaspiracids behave differently from other polyether toxins, and this accounts for most false-negative results in the mouse bioassay employed by regulatory agencies to detect azaspiracids. Typically, polyether toxins are concentrated in the digestive glands of shellfish, but this is not always the situation with azaspiracids. Liquid chromatography-mass spectrometry (LC-MS), especially multiple tandem MS methods, have been applied to demonstrate that azaspiracid (AZA1) and its methyl- and demethyl- analogues, AZA2 and AZA3 respectively, are distributed throughout shellfish tissues. Using conventional mouse bioassay protocols, only 0-40% of the total azaspiracid content of shellfish was used in the assay, which could directly account for false-negative results. It was also observed that the toxin profiles differed significantly in various mussel tissues with AZA1 as the predominant toxin in the digestive glands and AZA3 predominant in the remaining tissues.     

电喷雾质谱剖析烷基多苷的组成与

The identification of different components in raw alkyl polyglucosides(APGs) mixture were achieved by ESI-MS method.The APGs were ionized according to their different alkyl chain lengths and number of glucoside units.Individual components could be detected as cationized ions +,[M+NH4]+,+ or + in positive ion mode and as deprotonated ions in negative ion mode.In both ion modes the solute-solute clusters and fragments ions could be observed and their assignment was discussed.The distribution of alkyl chain length and polymerization degree of glucoside units could be qualitatively analyzed and the preparation approach(direct synthesis or transacetalization process) of APGs could be known.The highly sensitive ESI-MS analysis technique suits to rapid detection and quality control of APGs products.