Medium-Pressure Liquid Chromatography Coupled to Electrospray Ionization Mass Spectrometry for Separation and On-Line Characterization of Flavonoids from Asparagus officinalis

A novel method for separation and on-line characterization of flavonoids from Asparagus officinalis by medium-pressure liquid chromatography coupled to electrospray ionization multi-stage mass spectrometry (MPLC-ESI-MSⁿ) was successfully established. The hyphenation between MPLC and ESI-MSⁿ was designed to keep the split ratio exactly in the range from 1:100 to 1:300. The separation procedure was guided by the chromatogram of ion current of MSⁿ and the structures of compounds were characterized by fragments information at the same time. Consequently, it was proved that MPLC coupled with ESI-MSⁿ was an effective method for separation of compounds from multi-component mixtures with high purity and desired amounts and simultaneous elucidation of chemical structures.

     

Impurity Profiling of Dirithromycin by Liquid Chromatography Coupled to Electrospray Ionization Mass Spectrometry

The aim of this study was to characterize as much as possible the unknown peaks in the chromatogram obtained with a non-volatile LC-UV system, which was published earlier for the separation of dirithromycin and its related substances. For this purpose, each peak eluting from the non-volatile system was collected and transferred to a MS, after performing a desalting process. The desalting procedure uses a XTerra RP C₁₈ column (250 mm x 4.6 mm, 5 µm) and two mobile phases consisting of a mixture of water / 0.1% (v/v) formic acid and a mixture of acetonitrile / 0.1% (v/v) formic acid, respectively. Mass spectral data were acquired on an LCQ ion trap mass spectrometer equipped with an electrospray ionization source (ESI), operating in the positive ion mode. In addition to the thirteen already known compounds, seven new compounds were elucidated. Five impurities showed modifications at the amino group of the desosamine molecule, one an alteration at position C-9 and one a modification at position C-13 of the macrolide ring.     

大气气溶胶中有机碳和元素碳监测方法的进展

本文主要介绍和评述了近10年来大气气溶胶中的有机碳和元素碳的采样和分析技术的进展,引用参考文献41篇。     

OmniSpect: An Open MATLAB-Based Tool for Visualization and Analysis of Matrix-Assisted Laser Desorption/Ionization and Desorption Electrospray Ionization Mass Spectrometry Images

We present omniSpect, an open source web- and MATLAB-based software tool for both desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) that performs computationally intensive functions on a remote server. These functions include converting data from a variety of file formats into a common format easily manipulated in MATLAB, transforming time-series mass spectra into mass spectrometry images based on a probe spatial raster path, and multivariate analysis. OmniSpect provides an extensible suite of tools to meet the computational requirements needed for visualizing open and proprietary format MSI data.      

The Effect of Organic Modifiers on Electrospray Ionization Charge-State Distribution and Desorption Efficiency for Oligonucleotides

The chemical composition of the solution has a critical impact on the electrospray desorption efficiency of oligonucleotides. Several physiochemical properties of various organic modifiers were investigated with respect to their role in the desorption process of oligonucleotides. The Henry’s Law Constant, which reflects the volatility of alkylamines, was found to have a prominent effect on both the electrospray charge state distribution and desorption efficiency of oligonucleotides. Alkylamines with higher $ \mathrm{k}_{\mathrm{H,cc}}\left( {\mathrm{aq}/\mathrm{gas}} \right) $ values such as hexylamine, piperidine, and imidazole reduced the charge state distribution by forming complexes with the oligonucleotide and dissociating from it in the gas phase, while alkylamines with extremely low $ \mathrm{k}_{\mathrm{H,cc}}\left( {\mathrm{aq}/\mathrm{gas}} \right) $ values reduced the electrospray charge state distribution by facilitating ion emission at an earlier stage of the electrospray desorption process. Ion-pairing agents with moderate $ \mathrm{k}_{\mathrm{H,cc}}\left( {\mathrm{aq}/\mathrm{gas}} \right) $ values do not alter the electrospray charge state distribution of oligonucleotides and their ability to enhance oligonucleotide ionization followed the order of decreasing $ \mathrm{k}_{\mathrm{H,cc}}\left( {\mathrm{aq}/\mathrm{gas}} \right) $ values. The Henry’s Law Constant also correlated to the impact of the acidic modifiers on oligonucleotide ionization efficiency. Ionization enhancement effects were observed with hexafluoroisopropanol, and this effect was attributed to its low $ \mathrm{k}_{\mathrm{H,cc}}\left( {\mathrm{aq}/\mathrm{gas}} \right) $ and moderate acidity. The comprehensive effects of both alkylamine and hexafluoroisoproapnol on the electrospray ionization desorption of oligonucleotides were also evaluated, and acid-base equilibrium was found to play a critical role in determining these effects.      

自建电喷雾解吸电离源（DESI）在大分子分析中的应用及离子化机理探索

自建了简易的电喷雾解吸电离源(DESI),优化了DESI源喷口的位置和角度,并将其用于常见多肽和蛋白质的分析。多肽和小质量蛋白质(<20 kDa)可以容易地从表面解吸电离,生成清晰的质谱。而牛血清白蛋白(66.4 kDa)不能产生清晰的多电荷分布的质谱,说明当前DESI源的设计可能存在一个电离的分子量上限。通过比较不同的实验条件并对比ESI-MS,发现溶剂分子的挥发过程对电荷分布以及峰宽均有显著影响,可能是由于ESI更软引起。载样表面的性质对DESI-MS的信号强度有较大影响。金表面的自组装单分子膜(SAM)相对于纯金表面有较好的绝缘性,并有助于产生较强信号,说明来自表面的电子转移(电中和)是电喷雾解吸电离过程中的一个重要因素。该文的研究有助于对DESI-MS的实验条件和载样表面的选择,同时增进了对电喷雾解吸电离机理的了解。     

电喷雾解吸电离质谱法用于临床尿样的直接分析

将电喷雾解吸电离质谱(DESI-MS)用于临床尿样的分析, 优化了电喷雾溶剂流速、电喷雾电压和喷雾锥距离等重要参数. 采用普通滤纸作为样品载体, 在不需要样品预处理的前提下同时快速测定了临床尿样中的钾、钠、尿素、尿酸、丙酮酸和肌苷等多种成分, 并对各种成分的主要离子进行了串联质谱鉴定. DESI-MS在进行多组分同时测定时不需要进行样品预处理, 缩短了测定时间, 单个样品的分析时间不到1 min. 同时, 采用内标法对所测定组分进行了半定量分析.     

Laser Desorption Ionization Versus Electrospray Ionization Mass Spectrometry: Applications in the Analysis of Cluster Anions

Mass spectra of transition metal carbonyl cluster anions were recorded using laser desorption ionization time-of-flight (LDI-TOF) and electrospray ionization (ESI) techniques. The LDI spectra generally contain peaks corresponding the intact cluster together with extensive CO loss fragments ions whereas the ESI spectra exhibit peaks corresponding the intact cluster together with few (if any) CO loss fragment ions. The parameters of both techniques can be modified to vary the extent of fragmentation. In all cases no fragmentation of the metal core is observed. Overall, ESI is a more informative method for the analysis of these types of cluster anions.     

高效液相色谱-质谱联用技术同时测定人体尿液中11种代谢物

采用高效液相色谱-质谱联用技术定量检测人体尿样中丙烯醛、苯、1,3-丁二烯、苯乙烯、巴豆醛的巯基尿酸类代谢物及氰化氢代谢物。将解冻后的尿样经高速离心后,取100μL上清液,加入50μL内标溶液及850μL水后上样分析。色谱分析采用XSELECT HSS T3 C18色谱柱(150 mm×2.1 mm i.d,2.5μm),以乙腈-15 mmol醋酸铵溶液梯度洗脱,流速250μL/min,柱温40℃,在多反应监测模式(MRM)下采用负离子扫描模式进行定量分析。本方法共检测了16名吸烟者和6名非吸烟者的尿样,发现日吸烟量大于25支的吸烟者尿样中的烟气成分代谢物浓度高于非吸烟者。     

Coaxial Electrospray Ionization for the Study of Rapid In-source Chemistry

Coaxial electrospray has been used effectively for several dual-emitter applications, but has not been utilized for the study of rapid in-source chemistry. In this paper, we report the fabrication of a coaxial, micro-volume dual-emitter through the modification of a manufacturer’s standard electrospray probe. This modification creates rapid mixing inside the Taylor cone and the ability to manipulate fast reactions using a variety of solvents and analytes. We demonstrate its potential as a low-cost, dual-emitter assembly for diverse applications through three examples: relative ionization in a biphasic electrospray, hydrogen-deuterium exchange, and protein supercharging.

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Numerical Simulation of the Motion of Aerosol Particles in Open Cell Foam Materials

Russian Journal of Physical Chemistry A - The motion of aerosol particles in open cell foam material is studied. The porous medium is investigated for a three-dimensional case with detailed...     

Eluent Generator Reagent Free Ion Chromatography with Electrospray Ionization Mass Spectrometry for Simultaneous Analysis of Organic Acids in Juices and Beverages

A new analytical method is proposed for simultaneous determination of twenty organic acids in juices and beverages by eluent generator reagent free ion chromatography with electrospray ionization mass spectrometry (ESI–MS) in the negative selected ion monitoring mode (SIM). Twenty organic acids showed good linear relationship in the ranges of 0.5 ～ 20.0 mg/L. The correlation coefficients were more than 0.998, the detection limits were between 0.05 ～ 0.5 mg/L, and the average recoveries were between 88.0% ～ 106.0%. The relative standard deviations (RSDs) were less than 7.6%. The method has been applied to juice and beverage samples with satisfactory results.     

蛋白质非共价化合物的电喷雾质谱研究

介绍了近几年来利用电喷雾离子化质谱技术研究蛋白质的基本构象及蛋白质非共价化合物的基本化学信息的进展。许多研究表明,电喷雾质谱在研究蛋白质的复杂结构和功能方面有十分广阔的前景。文中列举了若干实例说明了电喷雾离子化质谱技术在分析蛋白质非共价化合物的应用和一般方法。     

The Development of a Sheathless Interface for Capillary Electrophoresis Electrospray Ionization Mass Spectrometry Using a Cellulose Acetate Cast Capillary

The fabrication of a novel sheathless interface for capillary electrophoresis–electrospray–mass spectrometry (CE–ESI–MS) is described. A programmable CO₂ laser was used to ablate small channels in the walls of a polyimide capillary near the terminus. Subsequent exposure of the channel region to a cellulose acetate solution followed by drying resulted in the formation of an electrically conductive semi-permeable membrane. Application of an appropriate voltage to the reservoir resulted in the simultaneous establishment of an electrical connection for CE and ESI. Interface viability was demonstrated by conducting a CE separation of a peptide mixture, with detection accomplished via positive ion mode ESI–MS. For the peptide Val-Tyr-Val, a limit of detection of 0.1 femtomole (S/N 3) was achieved using single reaction monitoring. Attributes of the interface include structural robustness, ease of fabrication, minimal interface dead volume, and the ability to alter post-separation analyte ionization status by use of appropriate buffers in the interface reservoir.     

Lipidomics of the Edible Brown Alga Wakame (Undaria pinnatifida) by Liquid Chromatography Coupled to Electrospray Ionization and Tandem Mass Spectrometry

The lipidome of a brown seaweed commonly known as wakame (Undaria pinnatifida), which is grown and consumed around the world, including Western countries, as a healthy nutraceutical food or supplement, was here extensively examined. The study was focused on the characterization of phospholipids (PL) and glycolipids (GL) by liquid chromatography (LC), either hydrophilic interaction LC (HILIC) or reversed-phase LC (RPLC), coupled to electrospray ionization (ESI) and mass spectrometry (MS), operated both in high and in low-resolution mode. Through the acquisition of single (MS) and tandem (MS/MS) mass spectra more than 200 PL and GL of U. pinnatifida extracts were characterized in terms of lipid class, fatty acyl (FA) chain composition (length and number of unsaturations), and regiochemistry, namely 16 SQDG, 6 SQMG, 12 DGDG, 5 DGMG, 29 PG, 8 LPG, 19 PI, 14 PA, 19 PE, 8 PE, 38 PC, and 27 LPC. The FA (C16:0) was the most abundant saturated acyl chain, whereas the monounsaturated C18:1 and the polyunsaturated C18:2 and C20:4 chains were the prevailing ones. Odd-numbered acyl chains, iJ., C15:0, C17:0, C19:0, and C19:1, were also recognized. While SQDG exhibited the longest and most unsaturated acyl chains, C18:1, C18:2, and C18:3, in the sn-1 position of glycerol, they were preferentially located in the sn-2 position in the case of PL. The developed analytical approach might pave the way to extend lipidomic investigations also for other edible marine algae, thus emphasizing their potential role as a source of bioactive lipids.     

Comparing the Effects of Additives on Protein Analysis Between Desorption Electrospray (DESI) and Electrospray Ionization (ESI)

It is frequently said that DESI-MS follows a similar ionization mechanism as ESI because of similarities usually observed in their respective mass spectra. However, practical use of DESI-MS for protein analysis is limited to proteins with lower molecular weights (<?25 kDa) due to a mass-dependent loss in signal intensity. Here we investigated commonly used volatile acids and their ammonium salt buffers for DESI-MS analysis of protein. We noticed that, surprisingly, some additives influence the analysis differently in DESI compared to ESI. Improved signal intensities with both DESI and ESI were obtained when acetic and formic acid were added into aqueous methanol spray solvents with both DESI and ESI. On the other hand, while with ESI the addition of ammonium salts into spray solutions strongly reduced both signal and S/N, with DESI signal intensities and S/N were improved dramatically. Ammonium bicarbonate when used with DESI reduced the total amount of adduction and delivered excellent signal-to-noise ratios with high intensity; however, it also denatures protein. When native state protein mass spectra are preferred, ammonium acetate would also deliver reasonable adduct removal and improved S/N. The amount of total adduction of individual adducting species and of all species could not be correlated with differences in either solutions pH values or with proton affinities of the anions. An obvious difference between DESI and ESI mass spectrometry is the effects of protein solubility during droplet pickup (desorption), but differences in the sizes, velocities, and composition of ionizing droplets were also discussed as important factors.

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Analysis of the Aconitine Alkaloids in Chuanwu by Electrospray Ionization ／ Tandem Mass Spectrometry

An electrospray ionization / tandem mass spectrometric (ESUMS/MS) method was developed for the simultaneous identification and analysis of three aconitine alkaloids [mesacontine (MA), hypaconitine (HA), and aconitine (A)] as intact molecules at low nanogram level in Chinese traditional medicine Chuanwu decoction as well as in human whole blood extract without chromatographic separation.     

Sensitivity of Positive Ion Mode Electrospray Ionization Mass Spectrometry in the Analysis of Thiol Metabolites

High signal intensities of glutathione (GSH), [GSH+H]⁺ (m/z 308), cysteine (CySH), [CySH+H]⁺ (m/z 122), and homocysteine (hCySH), [hCySH+H]⁺ (m/z 136), are observed in ESI MS with on‐line electrochemistry (EC). Dimers formed by H‐bonding, which are not electrochemical products, are detected as [2GSH+H]⁺ (m/z 615), [2CySH+H]⁺ (m/z 243) and [2hCySH+H]⁺ (m/z 271) together with disulfide dimers GSSG, CySSCy and hCySSCyh, [GSSG+H]⁺ (m/z 613), [CySSCy+H]⁺ (m/z 241) and [hCySSCyh+H]⁺ (m/z 269). When dopamine is present a thiol/dopamine quinone (DAQ) adduct is observed. Formation of this adduct is proposed to occur by an electrochemical mechanism during ESI. Catalysis of thiol oxidation and analysis of thiol mixtures is addressed.     

雪上一支蒿中乌头碱类生物碱的电喷雾串联质谱分析

利用电喷雾串联质谱(ESI-MS／MS)对雪上一支篙的乙醇提取液进行了直接分析,方法简便,直观,用样量少。ESL-MS可以给出分子量信息,MS／MS方法则可以从复杂体系中获得结构信息。在雪上一支蒿中发现乌头碱、去氧乌头碱及它们的水解产物和脂类生物碱等共19种二菇生物碱,其中脂类生物碱为首次在该植物中发现。     

北豆根生物碱电喷雾质谱电离规律及其特征图谱研究

用电喷雾离子阱质谱(ESI-QITMS)研究了粉防已碱和青藤碱在正离子检测方式下的一级质谱和二级质谱,总结出各自的ESI碎裂规律。依据北豆根对照药材生物碱提取物各组分的二级质谱碎裂特征进行了提取物的初步结构分析。实验发现北豆根提取物中存在曾在北豆根叶中发现的阿克吐明、阿克吐米定、阿克吐明宁3种含氯生物碱。以北豆根中16种已知主要生物碱(其中有一种存在同分异构体)为对象,应用选择离子检测(SIM)模式制作了北豆根对照药材生物碱提取物的特征指纹图谱。