A microcomputer current programmer for mass spectrometer direct exposure probes

An RCA Cosmac 1802 microcomputer has been used to program the sample heating wire current of a direct exposure probe used to obtain mass spectra of nonvolatile and thermally labile compounds. Programming is in machine language, which requires a minimum system, and is competitive in cost with hard-wired programmers, while possessing the flexibility available through software control. Current steps are synchronized with the rapid repetitive scanning of the mass spectrometer. The rapid desorption of the methyl ester of a bile acid is used for illustration of the operation.