【作者】 金伟；

【导师】 金钦汉；

【作者基本信息】 吉林大学 ， 测试计量技术及仪器， 2007， 博士

【摘要】 本论文结合电喷雾离子化离子阱质谱仪和便携式VOCs检测仪的研制任务,开展了其中几种关键部件的研制,取得了较好的结果。论文由两部分组成:第一部分:结合电喷雾离子化-矩形离子阱(RIT)质谱仪(ESI-RIT-MS)的研制,自行设计制作了一种易于加工、装调的矩形离子阱,同时与合作者一起开发了电喷雾离子化源(ESI)、截取器(Skimmer)、和六极杆等关键部件。申请发明专利二项。第二部分:一种以小型飞行时间质谱仪为基础的便携式VOCs检测仪关键部件的研制,开发了一种双层膜进样(MI)系统和有特色的电子轰击(EI)源。并申请发明专利一项。更多还原

【Abstract】 Part1: Development of key components of an ESI-RIT mass spectrometerThe most crucial components in ESI-RIT-MS is electrospray ionization (ESI), skimmer, hexapole, ion lens, rectilinear ion trap (RIT), gradient vacuum system and signal processing system. In this paper the first 5 components have been designed by the author according to the project requirements.1. Development of various kinds of soft ionization methods is now a hot study topic in mass spectrometry field. ESI has high sensitivity and reliable accuracy. In this paper an ESI source has been designed independently according to the requirements of the project.2. Skimmer plays a key role in forming gradient vacuum and separation neutral particles and ions. A processing technique for overcoming the difficulty of skimmer’s machining was developed in this paper and an innovation patent is pending.3. Hexapole has much better focus efficiency then quadrupole for ion transmission. The RF of hexapole can promise higher ions throughput and so can reduce the ion loss. Two processing techniques were developed to improve the sensitivity of the analyzer.4. An advanced RIT was designed, and machined and assembled independently. The RIT developed has larger ion storage space, smaller space-charge effect and is easier to be machined and assembled.5. The problem of having glow discharge in the second stage of the vacuum system was solved. The gradient vacuum formed is well suited to the introduction of ions from atmospheric pressure to vacuum system. And made the whole MS system work effectively.The ESI-RIT-MS platform developed has been tested. The developed prototype worked properly and it was shown that the mass range it could measure was up to 650(Figure 1). However, the mass resolution and sensitivity are still to be improved. Taking into consideration of the main factors affecting the performance of the instrument, our further study will focus on the improvement of materials performance used, machining precision of components, power stability, structural design of RIT and various circuit designs.Part2: Development of key components for an intelligent VOCs analyzerDuring the development of an intelligent VOCs analyzer some key components, such as membrane introduction (MI) of sample and electron impact (EI) ionization source are developed, and time-of-flight (TOF) mass analyzer and vacuum system are improved.1. Sample introduction include direct and indirect methods. Membrane introduction technique(MI)is a simple and mature sampling technique. By using this technique, the heavy turbo molecular pump and its power supply system are omitted, and it is very beneficial to the miniaturization of MS. The polydimethylsiloxane (PDMS) membrane we chose has a large permeation rate for VOCs molecules and small or zero permeation for background chemicals (especially, for N2 and O2). A double-membrane structure was adopted to keep vacuum system sealing and reduce the response time. Double-membrane structure divided vacuum chamber into a gradient vacuum with two stages. This reduces the thickness of the membrane used, only a 0.15mm thick membrane can keep a vacuum of 10-5Pa.2. A vacuum chamber was designed according to the requirement of the project. Taking into consideration of the merits of different pumps, a double-pump system consisting of a getter pump and a sputter ion pump has been used to keep the high vacuum. And then, the main requirements for processing and assembling the vacuum chamber were put forward.3. There are four kinds of ionization sources in common use: electron impact source(EI), chemical ionization(CI), adsorptions ionization (DI) and spray ionization(SI). Because of there are a great deal of advantages of EI, such as stable ion flow, higher ionization efficiency, better reproducibility, easy to be made and the fragments containing more information etc. An EI source with direct thermal cathode structure (made from rhenium wire) and auxiliary magnetic field has been independently developed.4. The structure of this VOCs has a time-of-flight mass analyzer which is relatively simple and has better mass resolution. The structure of orthogonal injection made all ions have the same initial velocity in drift tube. And a“Space Focus”is realized. and by utilizing reflective drift tube an“Energy Focus”is also realized.5. The ion detector used is a multichannel plate detector (MCP). The intelligent VOCs analyzer developed is based on a local control system, a data transmission system and a remote control system. The analytical to performance including detection limit, resolution, dynamic linear range, stability and remote monitoring operating parameters were all tasted.A preliminary study was also carried out and the results show that the prototype developed has a mass range up to 700(Figure 2) and could detect most volatile organic compounds with quite good detection limits(Table 1). This prototype has passed the check by the related authority and be accepted. It is currently the only miniature mass spectrometer whit a battery as a power supply in our country. It should be able to meet the needs of such fields as indoor and outdoor environmental monitoring, food safety and commodity inspection etc.更多还原