多喷嘴电喷雾阵列离子源对离子迁移谱性能的影响

采用多喷嘴电喷雾阵列作为离子迁移谱仪(IMS)的离子源以提高大气压下离子迁移谱的分析性能.12喷嘴的电喷雾阵列离子源内径为46μm,采用环形排列以提高喷雾电场的均匀度,喷嘴之间的距离为0.5 cm以克服喷嘴之间的电场屏蔽效应.测定了不同比例的甲醇作为ESI溶剂在2～ 30 μL/min流速及2.5～7 kV的喷雾电压下西地那非和苏丹红Ⅱ号的响应值及相应的信噪比.实验结果表明,在优化的条件下,多喷嘴电喷雾阵列可有效的提高ESI对溶液中水含量的容忍度,降低离子化噪音.与此同时,多喷嘴电喷雾阵列可使用更高的ESI流速.在相同的条件下,12喷嘴的电喷雾阵列离子源可提高离子化效率平均达3.8倍.     

电喷雾离子迁移谱检测氨基酸及多肽的研究

建立了氨基酸及多肽的电喷雾离子迁移谱检测方法.采用自制的电喷雾离子迁移谱装置,在室温条件下以甲醇为溶剂,空气为漂移气体,流速为1000 mL/min,电喷液流速为2 mL/min,测试了甘氨酸、胱氨酸、组氨酸、精氨酸4种氨基酸及缓激肽片段(1~7)和P物质2种多肽的离子迁移谱,计算出上述化合物的约化迁移率.离子迁移谱图反映出化合物的结构信息,具有指纹谱特征.此装置在1 min的检测时间内对P物质的检测灵敏度达到855 ng/mL.结果表明,电喷雾离子迁移谱可用于氨基酸及多肽类化合物的现场快速鉴定.     

离子淌度质谱技术及其应用研究进展

离子迁移谱（ion mobility spectrometry,IMS）是利用离子迁移率K（离子碰撞截面）差异来实现不同离子的分离与测定,具有分析速度快、检测灵敏度高的优点,其与质谱联用在蛋白质组学、代谢组学、医药等领域已获得了广泛的应用. 随着分析对象复杂性的增加,对IMS的分辨能力也提出了更高要求. 行波离子迁移谱（travelling wave ion mobility spectrometry,TWIMS）采用时域连续的行波电场实现离子传输与分离,其分析通道的长度不受行波电压幅值的限制,理论上可以无限延长离子分析通道来提高分辨能力. 目前,TWIMS的分辨率最高可达1 860,对于分析存在多种同分异构体的复杂样品别具优势. 对TWIMS的原理及分辨能力的影响因素进行了介绍,进一步探讨了不同结构TWIMS仪器的特点、性能和应用,对TWIMS未来发展方向进行了展望.     

RbCl由H2O至混合溶剂(H2O-DMF)标准迁移熵的测定

电解质迁移热力学性质的测定,对于离子溶剂化的研究具有重要意义.迁移自由能主要反映离子与溶剂分子间的相互作用,迁移熵则主要反映不同溶剂分子间的相互作用,迁移熵随温度及溶剂组成的改变可为溶剂的原有结构推测及溶液秩序改变提供信息.我们曾运用离子选择性电极测定了部分碱金属卤化物在水及含水混合溶剂中的热力学性质[1-3].本文用离子选择性电极方法,通过测定不同温度下电池的标准电动势,根据溶液热力学原理,求得ＲｂＣｌ由Ｈ2Ｏ至混合溶剂(Ｈ2ＯＤＭＦ)的标准迁移自由能ΔＧｔ及其温度系数,计算ＲｂＣｌ的标准迁移熵ΔＳｔ.结果尚未见…     

差分离子迁移谱和迁移时间离子迁移谱联用技术检测化学战剂模拟物

采用平板式差分离子迁移谱(DMS)和迁移时间离子迁移谱(DTIMS)联用技术(DMS-IMS2)对典型化学战剂模拟物甲基膦酸二甲酯(DMMP)和水杨酸甲酯(MS)进行测定。实验结果表明,在载气800 mL/min,DMS射频电压1100 V条件下,DMS-IMS2在DIMS模式能够实现DMMP和MS两种化学战剂模拟物的有效识别和检测。另外,DMS-IMS2能够实现DMMP和MS正、负离子的同时检测,同时获得DMMP和MS的DMS补偿电压(CV)和IMS迁移时间(Td)的二维分离信息,为两种化学战剂模拟物的准确鉴定提供更多的信息。DMS-IMS2具有二维分析能力、可同时分析正负离子、响应速度快、体积小、功耗低等优点,在现场检测中具有广阔的应用前景。     

纳升电喷雾-离子迁移谱及其与高效液相色谱的联用

搭建了一套纳升级电喷雾-离子源离子迁移谱仪。首先,分别对尾吹气流速、溶剂流速等影响仪器去溶剂化效果的参数进行了研究和优化。在此基础上,用一系列胺类化合物对该仪器的去溶剂化效果、分辨能力以及灵敏度进行了表征。实验结果表明,该仪器能够对电喷雾离子液滴实现完全去溶剂化;三辛胺的检出限可以达到10 μg/L。最后,将该仪器用作高效液相色谱的检测器,在无需衍生化的条件下对胺类混合物样品进行检测。由三乙胺、二乙胺以及丁胺组成的混合样品被成功分离并测定。该系统对三乙胺、二乙胺以及丁胺的线性响应范围均达到近两个数量级。     

液相色谱-电喷雾电离-离子迁移谱联用法测定中药口服液中7种指标性成分

采用液相色谱-电喷雾电离-离子迁移谱联用技术，研究建立了中药口服液中丹参素、甘草酸、天麻素、绿原酸、葛根素、黄芩苷、芦丁等7种指标性成分的二维分离分析方法。样品溶液首先经ACQUITY UPLC BEH C₁₈色谱柱（50 mm×1 mm，1.7 μm）分离后，导入可调节式分流器（分流比50 ∶ 1），柱后流出液分别进入离子迁移谱和三重四极杆质谱检测。分别详细优化了液相色谱、喷雾电压、迁移管和气体预加热温度、漂移气流速等实验条件，同时建立了指标性成分的液相色谱-三重四极杆质谱确证方法。7种中药指标性成分的检出限为2~10 μg/mL，定量限为5~25 μg/mL。采用本方法对中药口服液实际样品进行了检测分析。通过将液相色谱和离子迁移谱进行偶联，可实现目标化合物同时基于疏水性和离子迁移率差异的二维分离，获得更为丰富的测试信息。     

一种基于离子迁移谱的气相色谱检测器及其应用

离子迁移谱作为气相色谱的检测器,兼有色谱的高分离能力和离子迁移谱的高灵敏度,有利于实现复杂混合物的实时在线监测。基于在色谱、离子迁移谱方面的研究基础,本实验室搭建了一套以离子迁移谱为检测器的气相色谱仪,分别对检测器的温度、总电压、尾吹气流速等参数进行了系统优化,并用于碘甲烷、1,2-二氯乙烷、四氯化碳和二溴甲烷4种卤代烃化合物的检测。实验结果表明,参数优化后的离子迁移谱检测器对碘甲烷、1,2-二氯乙烷、四氯化碳和二溴甲烷的检出限可分别达到2、0.02、1和0.1 ng,线性范围有两个数量级。离子迁移谱与气相色谱联用,其二维的分离能力可以为复杂混合物的准确定性提供更多的信息,还可以实现不同化合物的选择性检测。     

NEWS

离子迁移谱(IMS)基于不同结构和质量的离子在均匀电场中的飞行速度差异实现不同化合物的分离分析,常被用于同分异构体的分离检测。除了独立使用之外,也常与质谱联用,例如在生物样品分析时,离子迁移谱可以显著降低背景噪声、提高检测灵敏度;离子迁移谱还被用作色谱检测器,实现复杂样品(特别是同分异构体)的多维分离。然而,     

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.     

Coupling of capillary electrophoresis with electrospray ionization multiplexing ion mobility spectrometry

In this work, ion mobility spectrometry (IMS) function as a detector and another dimension of separation was coupled with CE to achieve two‐dimensional separation. To improve the performance of hyphenated CE‐IMS instrument, electrospray ionization correlation ion mobility spectrometry is evaluated and compared with traditional signal averaging data acquisition method using tetraalkylammonium bromide compounds. The effect of various parameters on the separation including sample introduction, sheath fluid of CE and drift gas, data acquisition method of IMS were investigated. The experimental result shows that the optimal conditions are as follows: hydrodynamic sample injection method, the electrophoresis voltage is 10 kilo volts, 5 mmol/L ammonium acetate buffer solution containing 80% acetonitrile as both the background electrolyte and the electrospray ionization sheath fluid, the ESI liquid flow rate is 4.5 μL/min, the drift voltage is 10.5 kilo volts, the drift gas temperature is 383 K and the drift gas flow rate is 300 mL/min. Under the above conditions, the mixture standards of seven tetraalkylammoniums can be completely separated within 10 min both by CE and IMS. The linear range was 5–250 μg/mL, with LOD of 0.152, 0.204, 0.277, 0.382, 0.466, 0.623 and 0.892 μg/mL, respectively. Compared with traditional capillary electrophoresis detection methods, the developed CE‐ESI‐IMS method not only provide two sets of qualitative parameters including electrophoresis migration time and ion drift time, ion mobility spectrometer can also provide an additional dimension of separation and could apply to the detection ultra‐violet transparent compounds or none fluorescent compounds.     

Atmospheric-pressure ionization studies and field dependence of ion mobilities of isomeric hydrocarbons using a miniature differential mobility spectrometer

The ionization pathways and ion mobility were determined for sets of structural isomeric and stereoisomeric non-polar hydrocarbons (saturated and unsaturated cyclic hydrocarbons and aromatic hydrocarbons) using a novel miniature differential mobility spectrometer with atmospheric-pressure photoionization (APPI) to assess how structural and stereochemical differences influence ion formation and ion mobility. The analytical results obtained using the differential mobility spectrometry (DMS) were compared with the reduced mobility values measured using conventional time-of-flight ion mobility spectrometry (IMS) with the same ionization technique.The majority of differences in DMS ion mobility spectra observed among isomeric cyclic hydrocarbons can be explained by the formation of different product ions. Comparable differences in ion formation were also observed using conventional IMS and by investigations using the coupling of ion mobility spectrometry with mass spectrometry (APPI-IMS-MS) and APPI-MS. Using DMS, isomeric aromatic hydrocarbons can in the majority of cases be distinguished by the different behavior of product ions in the strong asymmetric radio frequency (rf) electric field of the drift channel. The different peak position of product ions depending on the electric field amplitude permits the differentiation between most of the investigated isomeric aromatics with a different constitution; this stands in contrast to conventional IMS in which comparable reduced mobility values were detected for the isomeric aromatic compounds.     

Monte Carlo simulation of ion transport in ion mobility spectrometry

A program for simulation of ion trajectories in ion mobility spectrometry (IMS) instruments has been developed and incorporated into SIMION 7.0 [Int. J. Mass Spectrom. 200 (2000) 3–25]. Simulations were based on elastic collisions between ions and gas particles and conducted for an IMS drift tube. The program was validated by comparing the reduced mobility of helium ions derived from the simulation with the experimental data for helium ions in neon drift gas in low electric fields. Typical IMS parameters, including pressure, temperature, and flow rate of the drift gas were taken into account in the simulations. The program demonstrates capabilities of generating IMS spectra and predicting ion transport efficiency and separating ions. For the IMS drift tube studied, a correlation between imperfection of the electric field distribution and low resolution has been observed.     

Time-of-flight ion mobility spectrometry and differential mobility spectrometry: A comparative study of their efficiency in the analysis of halogenated compounds

The ion mobilities of halogenated aromatics which are of interest in environmental chemistry and process monitoring were characterized with field-deployable ion mobility spectrometers and differential mobility spectrometers. The dependence of mobility of gas-phase ions formed by atmospheric-pressure photoionization (APPI) on the electric field was determined for a number of structural isomers. The structure of the product ions formed was identified by investigations using the coupling of ion mobility spectrometry with mass spectrometry (APPI-IMS-MS) and APPI-MS. In contrast to conventional time-of-flight ion mobility spectrometry (IMS) with constant linear voltage gradients in drift tubes, differential mobility spectrometry (DMS) employs the field dependence of ion mobility. Depending on the position of substituents, differences in field dependence were established for the isomeric compounds in contrast to conventional IMS in which comparable reduced mobility values were detected for the isomers investigated. These findings permit the differentiation between most of the investigated isomeric aromatics with a different constitution using DMS.     

Micro-plasma: a novel ionisation source for ion mobility spectrometry

Ion mobility spectrometry is an analytical method for identification and quantification of gas-phase analytes in the ppb_v-ppt_v range. Traditional ionisation methods suffer from low sensitivity (UV light), lack of long-term stability (partial discharge), or legal restrictions when radioactive sources are used. A miniaturised helium plasma was applied as ionisation source in an ion mobility spectrometer (IMS). Experiments were carried out to compare plasma IMS with β-radiation IMS. It could be demonstrated that the plasma IMS is characterised by higher sensitivity and selectivity than β-radiation ionisation. Plasma IMS is approximately 100 times more sensitive than the β-radiation IMS. Furthermore, variable sensitivity can be achieved by variation of the helium flow and the electric field of the plasma, and variable selectivity can be achieved by changing the electric field of the IMS. The experimental arrangement, optimisation of relevant conditions, and a typical application are presented in detail. Figure Micro-plasma used in ion mobility spectrometry     

Feasibility of higher-order differential ion mobility separations using new asymmetric waveforms

Technologies for separating and characterizing ions based on their transport properties in gases have been around for three decades. The early method of ion mobility spectrometry (IMS) distinguished ions by absolute mobility that depends on the collision cross section with buffer gas atoms. The more recent technique of field asymmetric waveform IMS (FAIMS) measures the difference between mobilities at high and low electric fields. Coupling IMS and FAIMS to soft ionization sources and mass spectrometry (MS) has greatly expanded their utility, enabling new applications in biomedical and nanomaterials research. Here, we show that time-dependent electric fields comprising more than two intensity levels could, in principle, effect an infinite number of distinct differential separations based on the higher-order terms of expression for ion mobility. These analyses could employ the hardware and operational procedures similar to those utilized in FAIMS. Methods up to the 4th or 5th order (where conventional IMS is 1st order and FAIMS is 2nd order) should be practical at field intensities accessible in ambient air, with still higher orders potentially achievable in insulating gases. Available experimental data suggest that higher-order separations should be largely orthogonal to each other and to FAIMS, IMS, and MS.     

Characterization of proton-bound acetate dimers in ion mobility spectrometry

Ionized acetates were used as model compounds to describe gas-phase behavior of oxygen containing compounds with respect to their formation of dimers in ion mobility spectrometry (IMS). The ions were created using corona discharge at atmospheric pressure and separated in a drift tube before analysis of the ions by mass spectrometry. At the ambient operational temperature and pressure used in our instrument, all acetates studied formed dimers. Using a homolog series of n-alkyl-acetates, we found that the collision cross section of a dimer was smaller than that of a monomer with the same reduced mass. Our experiments also showed that the reduced mobility of acetate dimers with different functional groups increased in the order n-alkyl 相似文献   

紫外离子迁移谱在线监测芳香族化合物

利用自制紫外离子迁移谱仪,在迁移电场为311V/cm、离子门开门时间0.2ms和室温的条件下,测定了空气中的苯、甲苯、二甲苯以及萘、芴、蒽、1,2,3-三氯苯、5-氯苯酚等芳香族化合物,得到苯的校正迁移率为1.86cm2V-1s-1,且校正迁移率随着分子量的增大而减小。仪器对苯的检出限达到1mg/m3;线性范围达到4个数量级;响应时间小于10s。研究发现,电场强度增大有利于提高仪器的灵敏度,测定时载气流速100mL/min,迁移气流速300mL/min时,效果最佳。     

Development of an ion mobility spectrometer for use in an atmospheric pressure ionization ion mobility spectrometer/mass spectrometer instrument for fast screening analysis

An ion mobility spectrometer that can easily be installed as an intermediate component between a commercial triple-quadrupole mass spectrometer and its original atmospheric pressure ionization (API) sources was developed. The curtain gas from the mass spectrometer is also used as the ion mobility spectrometer drift gas. The design of the ion mobility spectrometer allows reasonably fast installation (about 1 h), and thus the ion mobility spectrometer can be considered as an accessory of the mass spectrometer. The ion mobility spectrometer module can also be used as an independently operated device when equipped with a Faraday cup detector. The drift tube of the ion mobility spectrometer module consists of inlet, desolvation, drift, and extraction regions. The desolvation, drift and extraction regions are separated by ion gates. The inlet region has the shape of a stainless steel cup equipped with a small orifice. Ion mobility spectrometer drift gas is introduced through a curtain gas line from an original flange of the mass spectrometer. After passing through the drift tube, the drift gas serves as a curtain gas for the ion-sampling orifice of the ion mobility spectrometer before entering the ion source. Counterflow of the drift gas improves evaporation of the solvent from the electrosprayed sample. Drift gas is pumped away from the ion source through the original exhaust orifice of the ion source. Initial characterization of the ion mobility spectrometer device includes determination of resolving power values for a selected set of test compounds, separation of a simple mixture, and comparison of the sensitivity of the electrospray ionization ion mobility spectrometry/mass spectrometry (ESI-IMS/MS) mode with that of the ESI-MS mode. A resolving power of 80 was measured for 2,6-di-tert-butylpyridine in a 333 V/cm drift field at room temperature and with a 0.2 ms ion gate opening time. The resolving power was shown to be dependent on drift gas flow rate for all studied ion gate opening times. Resolving power improved as the drift gas flow increased, e.g. at a 0.5 ms gate opening time, a resolving power of 31 was obtained with a 0.65 L/min flow rate and 47 with a 1.3 L/min flow rate for tetrabutylammonium iodide. The measured limits of detection with ESI-MS and with ESI-IMS/MS modes were similar, demonstrating that signal losses in the IMS device are minimal when it is operated in a continuous flow mode. Based on these preliminary results, the IMS/MS instrument is anticipated to have potential for fast screening analysis that can be applied, for example, in environmental and drug analysis.     

A simulation model study of the coupled field in the IMS drift tube

The performance of the IMS was influenced by many parameters, like temperature, gas flow rate, etc. in the drift tube. An exact and comprehensive simulation model was very useful for the IMS design and optimization. A combined simulation model was build up for the parameters simulation in the drift tube. Based on this simulation model, the heat transfer, velocity distribution, humidity and ion transportation inside the drift tube in bidirectional flow stream was simulated, and the impact on the IMS was studied. And the simulation was also validated using an IMS constructed in our laboratory. The experiment showed that the RIP intensity weakened as the humidity increasing, but the signal intensity of NO was enhanced first, and then decreased with the humidity increasing sequentially. This can be explained from the simulation results. The simulation results showed that the distribution of the velocity and temperature was not uniformed in the drift tube. And this phenomenon was more clearly when the gas flow velocity increased. It can be seen from the simulation that the humidity in the drift tube region was smaller than the sample moisture, and the resolution of the ion mobility spectrometry will be reduced by the humidity. But in the region rich in water molecules, ultraviolet photons re-acting with acetone would be obviously decreased and fewer re-agent ions were produced owing to the strong absorption of photons by water neutrals. The results showed that the coupled field simulation model can be used to study parameters effects on the IMS.