MacMS is a program for Mac-OS compatible computers that simulates a magnetic sector mass spectrometer (1-4) designed to operate in the mass-to-charge (m/z) ratio range of 1-200 amu. MacMS has two operational modules. The first module (see Figure 1) is called the "Path" module and enables the user to quantitatively examine the trajectory of an ion of given m/z ratio in the electric and magnetic fields of the simulated "instrument". By systematically measuring a series of trajectories of different ions under different electric and magnetic field conditions, the user can determine how the resolution of the "instrument" is affected by these experimentally variable parameters. The user can thus choose suitable instrumental conditions for scanning a given m/z ratio range with good separation between the peaks.

The second module (see Figure 2) is called as the "Spectrometer" module and enables the user to record, under any chosen instrumental conditions, the mass spectrum of (i) the instrumental background, (ii) neon, (iii) methane, or (iv) the parent ion of carbon tetrachloride. Both voltage scanning and magnetic scanning are possible (5). A hard copy of any mass spectrum that has been recorded can also be obtained. MacMS can read ASCII data files containing mass spectral information of compounds other than those that are "built-in" to the simulator. The appropriate format for creating such data files is described in the program documentation.

There are a number of instructional exercises that can be conducted using the mass spectral information contained within the simulator. These are included in the program documentation. For example, the intensities of the ²⁰Ne⁺, ²¹Ne⁺, and ²²Ne⁺ species can be determined from hard copies of mass spectra of neon that are obtained under different instrumental sensitivities. The relative abundances of the three isotopes of neon can thus be calculated and compared with the literature values (6). The simulator also includes adjustable, fixed-value range and gain settings, which can be used to enhance the resolution and sensitivity of the instrument respectively.

Hardware and Software Requirements

Literature Cited

1. Kiser, R. N. Introduction to Mass Spectrometry and its Applications; Prentice-Hall: Englewood Cliffs, N. J., 1965; pp 1-3; pp 32-65.
2. Johnstone, R. A. W.; Rose, M. E. Mass Spectrometry for Chemists and Biochemists, 2nd ed.; Cambridge University Press: Cambridge, 1996.
3. Hill, H. C.; Loudon, A. G. Introduction to Mass Spectrometry; 2nd ed.; Heyden: London, 1972; p 5.
4. Farmer, J. B. In Mass Spectrometry, McDowell, C. A., Ed.; McGraw-Hill: New York, 1963; pp 10-11.
5. Message, G. M. Practical Aspects of Gas Chromatography-Mass Spectrometry, Wiley: New York, 1984; Chapter 3.
6. CRC Handbook of Chemistry and Physics, 55th ed.; CRC: Cleveland, 1974.