Modeling Study on the Entrainment of Ambient Air into Subsonic Laminar and Turbulent Argon Plasma Jets

Modeling study is performed to reveal the special features of the entrainment of ambient air into subsonic laminar and turbulent argon plasma jets. Two different types of jet flows are considered, i.e., the argon plasma jet is impinging normally upon a flat substrate located in atmospheric air surroundings or is freely issuing into the ambient air. It is found that the existence of the substrate not only changes the plasma temperature, velocity and species concentration distributions in the near-substrate region, but also significantly enhances the mass flow rate of the ambient air entrained into the jet due to the additional contribution to the gas entrainment of the wall jet formed along the substrate surface. The fraction of the additional entrainment of the wall jet in the total entrained-air flow rate is especially high for the laminar impinging plasma jet and for the case with shorter substrate standoff distances. Similarly to the case of cold-gas free jets, the maximum mass flow-rate of ambient gas entrained into the turbulent impinging or free plasma jet is approximately directly proportional to the mass flow rate at the jet inlet. The maximum mass flow-rate of ambient gas entrained into the laminar impinging plasma jet slightly increases with increasing jet-inlet velocity but decreases with increasing jet-inlet temperature.     

原位电离与小型质谱在公共安全领域的应用

质谱作为一种具有高准确度、高灵敏度、高选择性的检测仪器,在公共安全领域有着重要的应用前景。公共安全领域的需求主要涉及毒品、毒物、爆炸物等化学物质的现场快速检测,因其影响广泛,检测结果需非常准确。作为实验室分析仪器,质谱的准确性和速度能满足公共安全的应用需求,但作为现场快速检测的仪器仍需要一定改进。现场快速检测一方面要求检测仪器的小型化,另一方面要求样品前处理的简单化,以使整个检测流程可以无需专业人员来完成。对于检测仪器的小型化,小型质谱的开发在近20年得到了充分发展;对于样品前处理的简单化,研究者发明了原位电离技术,使得基质复杂的被分析物无需前处理即可进行质谱检测。该文首先介绍了原位电离技术的发展及其在公共安全领域的应用,特别是对解吸附电喷雾电离、实时直接分析电离、激光烧蚀电喷雾电离、纸喷雾电离与纸毛细管喷雾电离等典型原位电离技术的原理、性能及在公共安全领域的应用进行了详细介绍,并讨论了几种原位电离现场定量方法。然后,对原位电离小型质谱的发展进行了综述,从最初的小型化离子阱,到仅能检测可挥发有机物的小型质谱,再到可检测非挥发性物质的常规大气压电离源小型质谱,最后发展成为有原位电离源的小型质谱,历经20年的发展使得原位电离小型质谱得以出现和提升。并列举了原位电离小型质谱在毒品现场检测与吸毒人员排查、爆炸物现场侦察、食品安全之农用化学品检测、药物质量检查等公共安全领域的应用。最后,对原位电离小型质谱的发展进行了展望,指出原位电离与小型质谱相结合是小型质谱发展的必然趋势,未来需使用更加智能化的原位电离小型质谱,结合云数据平台,实现更方便广泛的应用。     

Ambient mass spectrometry: bringing MS into the “real world”

Mass spectrometry has recently undergone a second contemporary revolution with the introduction of a new group of desorption/ionization (DI) techniques known collectively as ambient mass spectrometry. Performed in an open atmosphere directly on samples in their natural environments or matrices, or by using auxiliary surfaces, ambient mass spectrometry (MS) has greatly simplified and increased the speed of MS analysis. Since its debut in 2004 there has been explosive growth in the applications and variants of ambient MS, and a very comprehensive set of techniques based on different desorption and ionization mechanisms is now available. Most types of molecules with a large range of masses and polarities can be ionized with great ease and simplicity with the outstanding combination of the speed, selectivity, and sensitivity of MS detection. This review describes and compares the basis of ionization and the concepts of the most promising ambient MS techniques known to date and illustrates, via typical analytical and bioanalytical applications, how ambient MS is helping to bring MS analysis deeper than ever into the “real world” open atmosphere environment—to wherever MS is needed.     

Direct Measurement of the Gas Entrainment Into a Turbulent Thermal Plasma Jet

An experimental study is conducted to investigate the entrainment characteristics of a turbulent thermal plasma jet issuing from a DC arc plasma torch operating at atmospheric pressure. The mass flow rate of the ambient gas entrained into the turbulent plasma jet is directly measured by use of the so-called “porous-wall chamber” technique. It is shown that a large amount of ambient gas is entrained into the turbulent plasma jet. With the increase of the gas mass flow rate at the plasma jet inlet or the plasma torch exit, the mass flow rate of entrained ambient gas almost linearly increases but its ratio to the jet-inlet mass flow rate decreases. The mass flow rate of the entrained gas increases with the increase of the arc current or jet length. It is also found that using different ways to inject the plasma-forming gas into the plasma torch affects the entrainment rate of the turbulent plasma jet. The entrainment rate expression established previously by Ricou and Spalding (J. Fluid Mech. 11: 21, 1961) for the turbulent isothermal jets has been used to correlate the experimental data of the entrainment rates of the turbulent thermal plasma jet, and the entrainment coefficient in the entrainment rate expression is found to be in range from 0.40 to 0.47 for the turbulent thermal plasma jet under study.     

Research Advances in Ambient Ionization and Miniature Mass Spectrometry

The development and applications of ambient ionization and miniature mass spectrometry are current research focus in chemical measurement. The analytical technology based on the combination of ambient ionization and miniature mass spectrometry can bypass chromatographic separation and eliminate or simplify sample pretreatment process. The protocol can reverse the labor-intensive and time-consuming drawbacks of traditional analytical methodologies, and realize rapid, on-site analysis with high sensitivity and high throughput. In this paper, the research progress and applications of ambient ionization and miniature mass spectrometry in the fields of food safety, consumer product safety, public security, life sciences and environmental monitoring, are reviewed, and future trends and prospects are discussed, which may provide technical guidance for the researchers engaged in relevant fields.     

Ambient ionisation mass spectrometry for the characterisation of polymers and polymer additives: A review

The purpose of this review is to showcase the present capabilities of ambient sampling and ionisation technologies for the analysis of polymers and polymer additives by mass spectrometry (MS) while simultaneously highlighting their advantages and limitations in a critical fashion. To qualify as an ambient ionisation technique, the method must be able to probe the surface of solid or liquid samples while operating in an open environment, allowing a variety of sample sizes, shapes, and substrate materials to be analysed. The main sections of this review will be guided by the underlying principle governing the desorption/extraction step of the analysis; liquid extraction, laser ablation, or thermal desorption, and the major component investigated, either the polymer itself or exogenous compounds (additives and contaminants) present within or on the polymer substrate. The review will conclude by summarising some of the challenges these technologies still face and possible directions that would further enhance the utility of ambient ionisation mass spectrometry as a tool for polymer analysis.     

复杂样品质谱分析技术的原理与应用

原位、实时、在线、非破坏、高通量、低耗损的质谱学方法是质谱分析技术发展的重要趋势.在无需样品预处理的条件下对复杂基体样品中痕量待测物直接离子化技术的出现,极大地提高了质谱分析的效率,使实际样品的快速质谱分析成为可能.本文着重综述了能够在无需样品预处理情况下对复杂基体样品离子化的新兴质谱技术及其应用研究,系统阐述了直接离子化技术的基本原理和方法,介绍了几种典型的常压直接离子化技术和装置,对直接离子化质谱分析技术在食品、药品、环境、活体分析、代谢组学、蛋白质组学以及生物组织质谱成像等领域的典型应用进行了述评,讨论了提高复杂样品快速质谱分析选择性的可能方法,并展望了常压直接离子化技术未来发展的可能趋势.     

Desorption sonic spray ionization for (high) voltage-free ambient mass spectrometry

Sonic spray ionization is shown to create a supersonic cloud of charged droplets able to promote efficient desorption and ionization of drugs directly from the surfaces of commercial drug tablets at ambient conditions. Compared with desorption electrospray ionization (DESI), desorption sonic spray ionization (DeSSI) is advantageous since it uses neither heating nor high voltages at the spray capillary. DeSSI therefore provides a more friendly environment in which to perform ambient mass spectrometry (MS). DeSSI-MS is herein evaluated for the analysis of drug tablets, and found to be, in general, as sensitive as DESI-MS. The (high) voltage-free DeSSI method provides, however, cleaner mass spectra with less abundant solvent cluster ions and with enough abundant analyte signal for tandem mass spectrometry (MS/MS). These features may therefore facilitate the DeSSI-MS detection of low molar mass components or impurities, or both. The higher-velocity supersonic DeSSI spray also facilitates matrix penetration thus providing more homogenous sampling and longer lasting ion signals.     

介质阻挡放电离子源质谱分析

敞开式离子化质谱可对表面样品进行直接快速分析而受到关注,成为质谱分析的热点研究方向.介质阻挡放电离子源是一种基于等离子体放电机理的敞开式离子源,近年来得到了较快的发展.本文着重介绍该离子源的基本原理、性能特征以及应用进展,并对其发展趋势进行了展望.     

Easy dual-mode ambient mass spectrometry with Venturi self-pumping, canned air, disposable parts and voltage-free sonic-spray ionization

An exceptionally easy to assemble source for ambient mass spectrometry is described. Based on Venturi easy ambient sonic-spray ionization (V-EASI), the source was further simplified by the use of a can of compressed air which simultaneously provides solution or solvent Venturi self-pumping and continuous, stable and abundant low-noise ion signal via voltage-free sonic-spraying. Further simplification was also attained by the use of inexpensive and readily commercially available parts: a surgical 2-way catheter, an aerosol can of compressed air, a 30 cm long fused-silica capillary and a hypodermic needle. This "Spartan" V-EASI source seems to offer one of the easiest and cheapest ways to make ions for ambient desorption/ionization mass spectrometry analysis of both liquid and solid samples.     

Ambient ionization mass spectrometry: a tutorial

Ambient ionization is a set of mass spectrometric ionization techniques performed under ambient conditions that allows the direct analysis of sample surfaces with little or no sample pretreatment. Using combinations of different types of sample introduction systems and ionization methods, several novel techniques have been developed over the last few years with many applications (e.g., food safety screening; detection of pharmaceuticals and drug abuse; monitoring of environmental pollutants; detection of explosives for antiterrorism and forensics; characterization of biological compounds for proteomics and metabolomics; molecular imaging analysis; and monitoring chemical and biochemical reactions). Electrospray ionization and atmospheric pressure chemical ionization are the two main ionization principles most commonly used in ambient ionization mass spectrometry. This tutorial paper provides a review of the publications related to ambient ionization techniques. We describe and compare the underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques.     

敞开式离子化质谱技术及其在微生物分析中的应用

敞开式离子化质谱(Ambient ionization mass spectrometry,AI-MS)是近年来兴起的质谱分析技术,可在敞开的大气环境下实现离子化,无需或只需少许样品前处理步骤,具有实时、简便、快速、高通量等诸多优点。近年来AI-MS技术的发展与应用已成为质谱领域备受关注的热点之一。该文综述了AI-MS的技术分类与原理特点,总结了AI-MS在微生物领域的应用。重点介绍了AI-MS在微生物种属鉴定与分型、微生物代谢物分析与生物膜分析、质谱成像等领域的应用。目前,环境电离与便携式质谱仪相结合已得到越来越广泛的应用,即将成为质谱领域的新热点。     

新型空气动力辅助离子源与不同类型质量分析器的快速接口技术

报道了新型空气动力辅助离子化(AFAI)装置与不同类型商业化质量分析器的快速接口技术. 在前期研究基础上, 进一步提高了AFAI系统的抽气流速, 在更宽范围内考察了流速对质谱灵敏度的影响; 对AFAI离子源进行模块化设计和制作, 重点解决快速接口问题, 通过更换接口板可实现其与不同厂家、 不同类型质量分析器的兼容及联用, 尤其可以与具有气帘接口的质量分析器联用. 本离子源装置结合不同质量分析器可以进行全扫描、 子离子扫描、 母离子扫描、 中性丢失扫描和高分辨等多种类型质谱分析, 而且AFAI可在电喷雾(ESI)、 解析电喷雾(DESI)和大气压化学电离(APCI)等多种离子化模式下工作, 从而实现对不同性质化合物的快速检测. 本研究结果进一步提高了AFAI离子化技术的功能, 拓展了其应用范围.     

大气环境中的水分子团簇分布和H+(H2O)n(n=4～16)离子的解离

报道了用质谱学方法首次测得的大气中各种水的团簇分布情况.表明在室内大气环境下,水主要是以几个至几十个水分子所组成的分子团簇的形式存在,且团簇的分布与空气湿度,即水在空气中的分压有关.实验中,除观测到空气中也存在前人已报道过的具有笼状结构的H+(H2O)21外,还观测到其他几种较稳定结构的水的团簇,即H+(H2O)4,H+(H2O)10和H+(H2O)15.实验中所测得的水分子团簇分布结果与使用的离子源以及质量分析器种类无关.我们还用碰撞诱导解离(CID)的方法研究了H+(H2O)n(n=4～16)离子的碰撞解离产物,结果表明,对于H+(H2O)n(n=4～16)的离子,其较稳定的离子的碰撞解离产物均为H+(H2O)n(n=4～6).我们还进一步研究了H+(H2O)10离子的碰撞解离产物与碰撞气体(即Ar气)密度的关系,得到了碰撞气体密度与碰撞解离产物分布的关系.     

Direct monitoring of drug degradation by easy ambient sonic-spray ionization mass spectrometry: the case of enalapril

Using enalapril maleate as a test case, the ability of ambient mass spectrometry, namely, via easy ambient sonic‐spray ionization mass spectrometry (EASI‐MS), to perform direct monitoring of drug degradation has been tested. Two manufacturing processes were investigated (direct compression and wet granulation), and the formation of degradation products was measured via both EASI‐MS and high‐performance liquid chromatography with ultraviolet detection for a total period of 18 months. Both techniques provide comparable results, which indicate that direct analysis by ambient mass spectrometric techniques presents a viable alternative for drug degradation monitoring with superior simplicity, throughput, and reliability (no sample manipulation), and comparable quantitative results. In terms of qualitative monitoring, the full mass spectra with intact species provided by EASI‐MS allow for comprehensive monitoring of known and unknown (or unexpected) degradation products. Copyright © 2011 John Wiley & Sons, Ltd.     

质谱技术在反应监测中的发展和应用

质谱因具有分辨率高、 灵敏度好、 响应快速以及结构鉴定能力强等特点, 近年来在反应监测研究领域应用广泛. 本文介绍了基于质谱的经典在线直接采样实时监测方案; 综合评述了常压质谱离子化技术在反应监测领域的发展和应用, 主要包括基于常压质谱的快反应监测、 微滴加速在长时间反应研究中的应用, 以及其它常压质谱在反应监测中的应用; 并对质谱在反应监测研究领域面临的挑战和发展趋势进行了总结和展望.     

敞开式离子化质谱在贸易产品化学风险物质筛查中的应用及前景

敞开式离子化质谱是一种新兴的质谱快检技术,具有分析速度快、操作流程简单、特异性强等特点。该技术无需对样品做复杂预处理,尤其在与便携式质谱仪联用时,可用于大量样品的现场、快速、准确筛查,在贸易产品化学风险物质的筛查中展现出广泛的应用前景。该文主要综述敞开式离子化质谱近年来在贸易产品化学风险物质筛查方面的研究进展,并对其未来的发展前景进行了展望。     

常压下能量与电荷在分子间的传递机制

离子源是质谱仪的心脏,制备待测物的离子是质谱分析的首要前提.如何有效地电离含有复杂基体的实际样品中的痕量待测物分子是制约实际样品直接质谱分析的重要瓶颈.本文提出了用电子云模型帮助理解能量与电荷传递和中性分子电离过程的关系,从分子的基本物性参数、能量耦合方式等角度讨论了能量与电荷在不同相态、组成和维度的复杂基体样品分子间传递的过程,着重阐述了能荷传递过程中分子的电子云变化规律及其对分子电离的影响,并简要讨论了这些影响在质谱分析中的应用.     

On-line analysis of ambient air aerosols using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy is developed for the detection of aerosols in ambient air, including quantitative mass concentration measurements and size/composition measurements of individual aerosol particles. Data are reported for ambient air aerosols containing aluminum, calcium, magnesium and sodium for a 6-week sampling period spanning the Fourth of July holiday period. Measured mass concentrations for these four elements ranged from 1.7 parts per trillion (by mass) to 1.7 parts per billion. Ambient air concentrations of magnesium and aluminum revealed significant increases during the holiday period, which are concluded to arise from the discharge of fireworks in the lower atmosphere. Real-time conditional data analysis yielded increases in analyte spectral intensity approaching 3 orders of magnitude. Analysis of single particles yielded composition-based aerosol size distributions, with measured aerosol diameters ranging from 100 nm to 2 μm. The absolute mass detection limits for single particle analysis exceeded sub-femtogram values for calcium-containing particles, and was on the order of 2–3 femtograms for magnesium and sodium-based particles. Overall, LIBS-based analysis of ambient air aerosols is a promising technique for the challenging issues associated with the real-time collection and analysis of ambient air particulate matter data.     

等离子体常压解吸离子源质谱

近年来,常压开源质谱解吸/离子化(ambient desorption/ionization mass spectrometry)技术的开发促进了质谱分析的蓬勃发展.作为常压开源质谱技术的一大重要分支,基于等离子体的常压质谱解吸/离子化技术因无需样品预处理、无溶剂化过程、高灵敏度、高通量、能实时在线检测样品等优点,受到了学术界及仪器制造、化学和生物分析等相关产业界的广泛关注.本文从离子源的种类、原理及应用等角度对目前我国在开源质谱领域中自主研发的基于等离子体的常压离子源的研究进展进行了总结,并对此类等离子体常压离子源的发展进行了展望,重点涉及微波等离子体源、常压微辉光放电等离子体源和解吸电晕束离子源.