High-Resolution Time-of-Flight Spectra Obtained Using the MULTUM II Multi-Turn Type Time-of-Flight Mass Spectrometer with an Electron Ionization Ion Source

Abstract

This paper describes experiments demonstrating the high mass-resolving power of the MULTUM II multi-turn type time-of-flight (ToF) mass spectrometer with a 1.308-meter circuit controlled by four toroidal electric sector fields¹ and an electron ionization (EI) ion source. A mass resolution of 250,000 [full-width at half maximum: (FWHM)] was obtained for N₂⁺ after a flight time of 9.0 ms (flight cycles: 1200, flight length: 1500 m). A doublet of ¹²C₅H₅¹⁴N and ¹³C¹²C₅H₆ (m/Δm = 9746; Δm: mass difference of doublet, m: mass of lighter ion of doublet) was separated and a mass resolution of 91,000 (FWHM) was obtained. A doublet of CDCl₂ and CH₂Cl₂ (m/Δm = 54,162) was also separated. A mass resolution of 115,000 (FWHM) was then achieved. When one peak of these doublets was used as a calibrant, the mass of the other peak was determined within a few ppm by mass difference. The ToF depending on the square of m/z was significantly larger than the systematic errors in the ToF, so that good mass accuracy was obtained by one-point mass determination.