Simultaneous analysis of butene isomer mixtures using process mass spectrometry

The feasibility of simultaneous analysis of mixtures containing two to four butene isomers and up to six total components using process mass spectrome try is assessed. As for typical (nonisomeric) applications of process mass spectrometry, simultaneous analysis is based on the assumption that the ele ctron ionization mass spectra of mixtures are Linear combinations of the sp ectra of the individual constituents. Limits of detection for binary isomer mixtures are on the order of 0.1% to 10%, Limited by the ability to distin guish small differences between similar spectra. As spectral and mixture co mplexity increase, both accuracy and precision decrease. Not surprisingly t he similarity of the spectra of stereoisomers cis- and trans-2-butene is gr eater than that of the other (nonstereoisomeric) isomer pairs, and mixtures containing both cis- and trans-2-butene are the most difficult to quantita te. However, even for mixtures of all four butenes, accuracy (root-mean-squ are error = 2.43%), precision (average coefficient of variation = 6.72%), a nd linearity (correlation coefficient of a plot of measured versus actual c oncentration r(2) = 0.985 +/- 0.002) are reasonably good. (J Am Soc Mass Sp ectrom 2000, 11, 1079-1085) (C) 2000 American Society for Mass Spectrometry .