表面解吸常压化学电离源的研制及应用

根据表面解吸常压化学电离源(SDAPCI)对表面痕量待测物进行常压解吸化学电离的原理,自行研制了SDAPCI电离源及其与线性离子阱(LTQ)质谱仪的接口,成功地在LTQ上实现了表面解吸常压化学电离。此方法无需样品预处理,直接利用电晕放电产生的H3O 在常压下对待测样品进行表面解吸化学电离,避免了甲醇等有毒试剂的使用。在优化的仪器参数条件下,分别用正/负离子模式成功地检测了片剂药品中的氯雷他定、乙酰氨基酚等活性成分和其它不同表面上TNT、氨基酸和多肽等物质,对这些常见物质的检出限不高于10pg/cm2。采用氩气作为电离试剂,观测到乙酰氨基酚、多肽等物质形成的自由基阳离子,提出了在氩气氛围中获得自由基阳离子的可能机理。实验表明SDAPCI具有灵敏度较高,选择性好,适用范围宽等特点,适合用于药品、食品等非破坏、无污染检测以及对复杂基体物质进行快速现场分析。     

液相色谱-大气压化学电离飞行时间质谱分析氢化可的松中微量杂质

大气压化学电离是1种较软的离子化方法,溶剂在雾化气及加热的作用下雾化,并迅速汽化.在大气压状态的区域内,汽化的分子在高电压条件下相互间发生碰撞及电荷转移,形成等离子体.样品分子M通过这一区域时与其反应,从而实现离子化,产生[M+H]+或[M-H]-准分子离子.为了进一步了解样品分子结构,采用源内碰撞诱导的技术即在离子源内增加喷口的电压,使分子离子碰撞裂解产生碎片离子.综合检测到的准分子离子和碎片离子信息,可更多地了解所测分子的结构信息.氢化可的松为肾上腺皮质激素类药物,有抗炎和抗风湿作用,亦称抗炎激素.在药品生产过程中,由于原料、副反应等因素引入了一些杂质.液质联用的方法可以简单、快速地提供这些杂质的分子信息.     

大气压化学萃取电离质谱法用于吡啶类化合物的快速检测

利用大气压化学萃取电离源质谱技术(EAPCI-MS)对吡啶类化合物的电离行为特征进行研究。实验显示,EAPCI-MS技术在常温常压条件下,无需样品预处理和任何辅助化学试剂,在质谱图中能同时检测到吡啶类化合物的质子化分子离子峰[M+H]+和分子离子峰M+·,并具有类似的二级碎裂机理。研究结果表明,EAPCI-MS技术具有不同于传统电离源质谱的裂解方式,同时兼具传统电喷雾电离(ESI)和大气压化学电离(APCI)的特征电离方式和行为,极大地提高了化学检测的选择性,增强了质谱分析的定性能力。该研究为吡啶类化合物的检测和鉴定提供了一种新方法,对吡啶类化合物的快速检测具有重要的应用价值和意义。     

石油芳烃组分中未知化合物——三叔丁基苯基磷酸酯的高分辨质谱分析

将大气压光电离(APPI)、电喷雾(ESI)、实时直接分析(DART)多种电离源和傅立叶变换离子回旋共振质谱(FT-ICR MS)联用对石油芳烃样品中的未知化合物进行研究。通过高分辨质谱的精确质量,结合碰撞诱导解离(CAD)技术,经分析并与文献标准物质谱图比对,推断未知物为三(2,4-二-叔丁基苯基)磷酸酯(TDTBPP),并研究了其在不同大气压电离源中的电离特性。APPI谱图中主要为[M+H]~+峰,同时存在M.~+峰。ESI谱图中主要为[M+Na]~+(不加甲酸)或[M+NH4]~+峰(加甲酸)。DART谱图中主要为[M+NH4]~+峰,而EI谱图中基峰为m/z 57(叔丁基),次强峰为[M-CH3]~+峰。     

非接触热解析封闭式低温等离子体电离源质谱法快速分析3种农药残留

利用低温等离子体电离源微型离子阱质谱建立了一种常压离子化质谱直接、快速、定量分析农药残留的新方法。低温等离子体电离源与质谱进样口处于封闭金属腔体内部,在负离子探测模式下,将样品放置于低温等离子体电离源前的采样平台上,利用卤素灯快速无接触热解析样品。结果表明,封闭离子源更具优势,通过对加热时间、辅助气流流量等条件的优化,实现了对3种农药在0.5~10 mg/L范围内的定量分析,相对标准偏差控制在11%左右,5 s内的样品检出限均在pg量级。该检测方法无需样品前处理,样品可直接检测,分析时间快,有望广泛应用于有机和绿色果蔬中农药残留的快速检测。     

热解析低温等离子体电离源用于糯高粱中农药残留的快速筛查

本研究设计并搭建了一套热解析低温等离子体电离源(TD-LTP),与质谱联用实现了糯高粱中农药残留的快速和高灵敏检测.TD-LTP由热解析装置和低温等离子体放电源两部分组成,农药残留样品首先在热解析进样器内汽化,再由载气载带进入等离子体区域被电离.热解析进样器使LTP产生的气相等离子体与样品之间的气-固或气-液相互作用转变为气-气相互作用,大大提高了难挥发样品(如农药)的电离效率;电离源与质谱进样口之间采用同轴连接,提高了离子的利用率和传输效率.与传统的LTP电离源相比,TD-LTP电离源的灵敏度提高了8倍以上,稳定性提高了4倍.本研究对热解析低温等离子体电离源的各参数进行了优化,并与自制的矩形离子阱质谱相结合,研究了12种农药在该电离源下的特征离子.最后,将此电离源与商品化的三重四极杆质谱仪联用,对糯高粱样品中的12种农药残留进行了快速筛查,结果表明,本方法灵敏度高,可以满足食品安全国家标准规定的谷物中农药残留最大限量检测要求.     

一种新型二次离子质谱的一次离子源及其离子光学系统

本研究设计了一种新型用于二次离子质谱的一次离子源及其离子光学系统.通过此一次离子源,大气压下产生的一次离子可以被加速、聚焦并传输到位于真空条件下的样品表面并电离样品得到可供质谱仪分析的二次离子.通过理论模拟结合实验系统研究了此一次离子源的主要组成部分——离子光学系统的原理、结构和性能.以电喷雾电离源为例,成功地将大气压...     

在线气体分析的电晕放电大气压电离质谱

研制了适合在线气体分析的电晕放电大气压电离源(corona discharge atmospheric pressure ionization source)及其与商品质谱仪(LTQ-MS)的接口,对其试剂离子的产生机理进行了研究,以H2O. (H2O)为试剂离子,对乙醇气体进行检测,并分析了该离子的产生机制。实验结果表明:在潮湿氮气中电晕放电产生的主要试剂离子是m/z36、37和55;而在含丙酮的潮湿氮气中则产生m/z59和76等离子。利用静态顶空-电晕放电大气压电离质谱对不同浓度的乙醇水溶液进行分析,结果表明:以m/z64为检测对象,乙醇气体浓度的最低检出限可达2.4×10-7g/L;而以m/z47为检测对象,检出限为5.9×10-6g/L。同时还利用动态顶空-电晕放电大气压电离质谱对栀子花香气成分进行了检测,为生物挥发性物质的在线检测提供了一种新方法。     

调控微波等离子体能量进行药片活性分子结构的质谱分析

采用微波等离子体质谱(MPT-MS)技术,对替硝唑和马来酸氯苯那敏药片进行快速质谱分析.通过调控等离子体能量,在一级谱图中可得到目标物的准分子离子及丰富的碎片离子,这些碎片离子与其对应串联质谱数据基本一致,甚至更加丰富;结合标准品比对分析,最终确定这些碎片离子来自目标物而非基质.因此,MPT兼具硬电离和软电离性质,采用MPT-MS技术从一级质谱图中获得的数据可对药片中活性分子的结构进行鉴定.该方法具有快速、准确及环保等特点,在发展MPT与简单的质量分析器联用,实现质谱仪的小型化等方面有广阔的应用前景.     

大气采样辉光放电质谱仪的设计与应用

针对某些弱极性类物质难以通过大气压离子源直接电离的问题,提出基于大气采样辉光放电电离方式实现弱极性物质在大气压下直接进样、电离和质谱分析的方法.通过在大气压接口-四极质谱仪的第一级真空中的离子透镜上施加交流高压产生放电,简化了辉光放电离子源的设计,能直接离子化大气压接口吸人的物质,离子在离子透镜的传输下进入四极杆质量分析器实现质谱分析.实验表明,本方法能电离电喷雾电离离子源和大气压化学电离离子源未能电离的弱极性物质——艾试剂,并且负离子工作模式比正离子工作模式的信号至少强40倍.     

Atmospheric identification of active ingredients in over-the-counter pharmaceuticals and drugs of abuse by atmospheric pressure glow discharge mass spectrometry (APGD-MS)

Atmospheric pressure glow discharge mass spectrometry was used to characterize the active ingredients in pharmaceutical over-the-counter (OTC) drug formulations (Tylenol Allergy, Alka-Seltzer Plus Nighttime, Sudafed, Aleve and Mucinex DM) and drugs of abuse (crack cocaine, methamphetamine, MDMA (ecstasy) and hydrocodone). Material was desorbed and directly ionized under atmospheric conditions by allowing the substance to come in direct contact with the plasma followed by mass spectrometric detection. With this technique, controlled substances and OTC medications were readily distinguished from one another. Characteristic mass spectra were identified for the active ingredients in the OTC and drugs of abuse. Importantly, all drug compounds studied here, both OTC and illicit, demonstrated signals for either molecular ions or protonated molecules as well as fragmentation patterns that are readily identified in the National Institute of Standards and Technology (NIST) electron ionization (EI) mass spectral library. It is believed that this technique holds promise for forensic and law enforcement communities for real-time atmospheric analysis of drugs with database-searchable spectra of controlled substances.     

Atmospheric pressure microwave induced plasma ionization source for molecular mass spectrometry

An atmospheric pressure microwave induced plasma ionization (AP-MIPI) source design for molecular analysis is presented. It consists of three sections: the torch, the microwave cavity, and the vacuum interface. The torch uses an oscillating capillary nebulizer for introduction of aqueous solutions into the afterglow of the MIP. Samples introduced into the afterglow of the plasma are ionized by protonated solvent molecules in a fashion similar to the chemical ionization process. The ions are then transported into the mass spectrometer using a heated capillary tube. The combination of an improved torch design and the heated capillary tube provides a stable ionization source for direct aqueous solution introduction with flow rates of up to 0.5 mL/min. The system works well with solvent compositions similar to those used in high performance liquid chromatography. For most samples studied, the protonated molecules were the base peaks of the mass spectra. A linear dynamic range of at least two orders of magnitude and an upper limit of quantitation of 5 ng were observed for alanine. The technique was shown to maintain reproducibility and moderate loss of sensitivity (33% reduction) when an amino acid solution containing a sodium phosphate buffer was analyzed. The optimization of experimental parameters with respect to the torch and vacuum interface is discussed.     

Direct desorption/ionization of analytes by microwave plasma torch for ambient mass spectrometric analysis

Ambient ionization is the new revolution in mass spectrometry (MS). A microwave plasma produced by a microwave plasma torch (MPT) at atmospheric pressure was directly used for ambient mass spectrometric analysis. H₃O⁺ and NH₄⁺ and their water clusters from the background are formed and create protonated molecules and ammoniated molecules of the analytes. In the full‐scan mass spectra, both the quasi‐molecular ions of the analytes and their characteristic ionic fragments are obtained and provide evidence of the analyte. The successful detection of active compounds in both medicine and garlic proves that MPT has the efficient desorption/ionization capability to analyze solid samples. The obtained decay curve of nicotine in exhaled breath indicates that MPT‐MS is a useful tool for monitoring gas samples in real time. These results showed that the MPT, with the advantages of stable plasma, minimal optimization, easy, solvent‐free operation, and no pretreatment, is another potential technique for ambient MS. Copyright © 2013 John Wiley & Sons, Ltd.     

Atmospheric pressure laser desorption/chemical ionization mass spectrometry: a new ionization method based on existing themes

We have designed and constructed an atmospheric pressure laser desorption/chemical ionization (AP-LD/CI) source that utilizes a laser pulse to desorb intact neutral molecules, followed by chemical ionization via reagent ions produced by a corona discharge. This source employs a heated capillary atmospheric pressure inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. Preliminary results demonstrate that this technique provides approximately 150-fold increase in analyte ions compared to the ion population generated by atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI).     

Spectroscopic characterization of a microplasma used as ionization source for ion mobility spectrometry

We report a miniaturized excitation source for soft ionization of molecules based on a dielectric barrier discharge. An atmospheric plasma is established at the end of a 500 μm diameter capillary using He as buffer gas. The plasma jet which comes out of the capillary is dependent on the gas flow rate. The mechanism of the production of N₂⁺ outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated by spatially resolved spectroscopic measurements throughout the plasma. Possible application of such miniaturized plasmas is the ionization of gaseous compounds under atmospheric pressure as an alternative to traditional APCI (atmospheric pressure chemical ionization). The miniaturized plasma was applied as ionization source for ion mobility spectrometry where the common sources are radioactive, thus limiting the place of installation. First measurements of gaseous compounds with such a plasma ion mobility spectrometer with promising results showed detection limits comparable or even better than those obtained using common radioactive ionization sources.     

Immobilized artificial membrane chromatography coupled with atmospheric pressure ionization mass spectrometry

Liquid chromatographic separations on monolayers of cell membrane phospholipids covalently immobilized to silica particles at high molecular density is used for mimicking solute partitioning into biological membranes that generally correlates with membrane transport. This technique called immobilized artificial membrane chromatography usually employs ultraviolet (UV) detection where a single compound is analyzed in a chromatographic run limiting thereby its throughput for drug discovery applications. For coupling with atmospheric pressure ionization mass spectrometry, the phosphate-buffered saline mobile phase was replaced with one that used ammonium acetate as a volatile buffer. While atmospheric pressure chemical ionization accommodated a purely aqueous effluent, interfacing with electrospray ionization required effluent splitting and the addition of an organic modifier (5%, v/v, acetonitrile). Neuropeptide FF antagonists as early-phase drug candidates were used for the comparative evaluation of the methods. Whereas electrospray ionization produced essentially no fragment ions, several compounds involved in our study yielded low-abundance molecular ions with atmospheric pressure chemical ionization. The use of mass spectrometry yielded data that correlated well with those obtained by the method employing UV detection. Both atmospheric pressure ionization methods permitted the simultaneous determination of the k'(IAM), capacity factors and, therefore, an increased-throughput ranking of potential new leads emerged from the drug discovery process based on affinity to artificial membranes.     

全氯代多环芳烃的大气压化学电离质谱

８种全氯代多环芳烃的大气压化学电离质谱（ＡＰＣＩ－ＭＳ）测试结果表明,在ＡＰＣＩ离原中,所有全氯代多环芳烃均能形成质量较样品分子量少１９的负离子,该类负离子是样品分子离子解离一个氯原子后再结合一个氧原子的产物。当样品含有一个五元环时,仍能观察到样品的分子离子峰。ＡＰＣＩ－ＭＳ是一种全氯代多环芳烃或其它弱极性有机物的理想质谱分析方法。     

On-line characterization of gaseous and particulate organic analytes using atmospheric pressure chemical ionization mass spectrometry

A modified atmospheric pressure chemical ionization ion source is applied for direct analysis of volatile or low volatile organic compounds in air. The method is based on the direct introduction of the analytes in the gas phase and/or particle phase into the ion source of a commercial ion-trap mass spectrometer. Two methods are employed for the production of primary ions at atmospheric pressure, photoionization and corona discharge. It is shown that in the presence of a dopant, photoionization can be a highly efficient ionization method also for real-time analysis with detection limits for selected analytes in the lower ppt-range. Using corona discharge for the production of primary ions, which is instrumentally easier since no additional chemicals have to be added to the sample flow, we demonstrate the analytical potential of on-line atmospheric pressure chemical ionization mass spectrometry for reaction monitoring experiments. To do so, an atmospherically relevant gas phase reaction is carried out in a 500 l reaction chamber and gaseous and particulate compounds are monitored in the positive and negative ion mode of the mass spectrometer.