An experiment for the quantitative determination of two co-eluting isomers, which are 3-pentanone and valeraldehyde, by using extract ion chromatogram in gas chromatographmass spectrometry (GC–MS) is described. The application is carried out by the internal standard method and the importance of molecular ion fragmentation via McLafferty rearrangement is emphasized. The unknown concentrations are readily calculated from the calibration curves generated by the students and compared with the actual data. The powerful capability of extract ion chromatogram in chemical analysis is appropriately demonstrated by this experiment, which can be fit into one session of the undergraduate instrumental analysis laboratory or other related scientific classes.
Ji et al. (Tue,) studied this question.