Journal of the Mass Spectrometry Society of Japan
Online ISSN : 1880-4225
Print ISSN : 1340-8097
ISSN-L : 1340-8097
59 巻, 2 号
選択された号の論文の2件中1~2を表示しています
技術報告
  • 林 雅宏, 内藤 康秀
    2011 年 59 巻 2 号 p. 23-33
    発行日: 2011/02/01
    公開日: 2011/04/15
    ジャーナル フリー
    Simultaneously detecting arrival times and two-dimensional (2D) positions of individual ions is essential for imaging mass spectrometry (imaging MS) in the microscope (stigmatic) mode which is superior in terms of spatial resolution to the more commonly used microprobe mode imaging MS. A detection system for microscope mode imaging MS was developed using an in-house constructed laser desorption/ionization (LDI) linear time-of-flight mass spectrometer as a platform for use and a delay line detector (DLD) was used as the position-sensitive ion detector. A signal readout system for DLD was configured using high-speed analog-to-digital converter (ADC) modules to detect multiple m/z-resolved ions. An efficient acquisition/processing technique for the data, which was acquired using an ADC-based system was developed to achieve an increased permissible laser pulse repetition rate, reduced data size and real time data processing. Multiple stigmatic images of m/z-resolved ions were obtained from a model sample formed of micro-dots of three types of dyes without using an ion gate for m/z selection. The measurement time was 18 minutes at an ionizing laser pulse repetition rate of 10 Hz, and the size of the data, which was comprised of lists of flight times and 2D positions of individual detected ions in ASCII format, was below 5 MB. The ability of LDI microscope mode imaging MS to obtain a complete series of m/z-resolved snapshots of LDI-generated ions in a single measurement was demonstrated. The present approach provides a realistic solution that can make use of a high-speed ADC for the DLD signal readout, and may facilitate further technical developments of microscope mode imaging MS.
総説
  •  
    長尾 敬介
    2011 年 59 巻 2 号 p. 35-49
    発行日: 2011/02/01
    公開日: 2011/04/15
    ジャーナル フリー
    The basic physical aspects of atoms and isotopes, as well as the physical and chemical processes responsible for variations in isotopic ratios are overviewed. The major techniques in current use for isotope ratio measurements are stable isotope mass spectrometry (MS), noble gas MS, thermal ionization MS, inductively coupled plasma MS, secondary ion MS, and accelerator MS. The types of ion sources suitable for use in isotope ratio MS are electron ionization for gases, thermal ionization for non-volatile elements, inductively coupled plasma ionization for the majority of elements, and sputtering ionization by means of a high energy positive or negative ion beam for solid target elements. A variety of ion detection methods using a Faraday cup, a Daly collector system, and an ion counting system with a secondary electron multiplier are capable of covering a wide dynamic range of ion beam intensity, from ∼10-8 to ‹10-19 A. Methods used for data processing and for evaluating the reliability of data for the isotope ratios that are obtained using MS are described.
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