Determination of the double bond position in monounsaturated acetates from their mass spectra

A simple method of widespread applicability in determining double bond positions in C12, C14, and C16 straight-chain monounsaturated acetates is presented. The analysis is made with a capillary gas chromatograph coupled to a low-resolution mass spectrometer which is operated in the electron impact mode. No chemical derlvatlzation of the unknowns is needed. Five pairs of selected mass spectral fragments are chosen to distinguish positional isomers. A new mathematical model is introduced which permits simultaneous comparisons of all five ratios of unknowns and references. The method can be used for analyses of very small amounts (<5 ng) of unknown acetates in insect samples