A Simple Display System for Recording Rapid Changes in Mass Spectra

摘要

A convenient photographic readout for recording rapidly changing mass spectra (of the order of milliseconds) generated by a time-of-flight instrument is achieved by a combination of two oscilloscopes equipped with Polaroid Land cameras. One of the oscilloscopes is operated by established techniques to display, quantitatively, peak height versus time for any one of the preselected mass peaks. Simultaneously, the second oscilloscope in the system displays a raster presentation of approximatepeak height of all the peaks in the spectrum as afunction of time. In the latter case, the discrete m/e values are displayed on the horizontal axis as dots and the magnitude of the ion peaks is displayed semiquantitatively by z-axis modulation (intensification of the dots), while time is presented as the trace is displaced vertically by a raster voltage which is synchronized with the time base of the first scope. The z-axis circuitry has been employed to further advantage by applying it to the monitoring oscilloscope during the customary timeof-flight spectral presentation (ion-peak height versus m/e) to intensify all the peaks of the oscilloscopic display, thus enhancing visual observation and photographic recording for all operations of the mass spectrometer. The system is described, and several applications to the rapid analysis of gaseous products resulting from the millisecond-duration flash pyrolysis of polymers are presented. (Author)