Mass Spectra Analysis Using a Programmable Calculator The analwis of a mass snectrum hv.assienment of all nossible atomic arrangements can be quite tedious and subiect t o
errors nf o m i k o n as well aserrors due to imorohable assiened comhinations.~hecaoabilities of modern handheld nro-
values (12). A program has been designed, based on the Hewlett-Packard HP-25 scientific programmable calculator in which the Reverse Polish Notation (RPN) is used. The program is designed to ealculste all the possible combinations of carbon, hydrogen, and oxygen that might account for a given mass measurement. The program utilizes three simple chemical rules: 1) There must he a t least one carbon atom in the formula, and the number of carbon atoms, N,, cannot exceed the maximum allowable number, N, where N is determined by the mass: 1 5 N , 5 N . 2 ) The number of hydrogen atoms, Nh, must he no more than 2 N , 2, for a saturated carbon compound or mass fragment: 0 5 N h 5 2N. 2. 3) The number of oxygen atoms, No, must he no more than 2 N , for a saturated carbon compound or mass fragment: 0 5 N , 5 2N,. These rules will avoid the assignment of chemically improhahle structures. The following assignments to mass identifications are not covered by these rules: H, 0 , OH. However, this is not a crucial matter since only three well-known masses, 1,16, 17, are involved, and the investigator would normally he aware of these possibilities. The theoretical mass for each combination of N,, Nh, No can he calculated with a few keystrokes, using stored and computed data. The total number of rings and double bonds can also he determined with a few keystrokes. We have described here a procedure for analyzing mass spectra with the utilization of a programmable calculator. This procedure is particularly suitahle for a small mass spectrometer laboratory where access t o a large computer is not possible. Analysis of mass spectra can he performed in the lahoratory by students under optimal learning conditions. Copies of the program listing and documentation are available, free of charge, upon request, from A. E. Attard.
+
+
Literature Cited (11 (21 (3) (41 (51 (6)
"HP-25 Owner's Handhmk," Hewlett-Packard, Cupertino. California, 1975. "HP-25 Applications Programs: Hewiett-Packard, Cupertino, California, 1975. Fuwler, R. W., "A Collection of HP-25 Routinen: R. W. Fowler, Silver Springs, MD.. 1976. Schmidt, S. A.,Am. J. Physics, 45.79 (19771. Murgieh.J.. J. CHEM.EDUC.54.421 (1977). Smith, J. W., "Scientific Analysis on the Pocket Calculator: John Wiley & Sans. New York. 1915.
Department of Forensic Science Center for Annlied .. Research University of New Haven New Haven, Connecticut 06516
428 / Journal of Chemical Education
Alfred E. Attard Henry C. Lee
