Chemical analysis of fresh and aged Australian e‐cigarette liquids

To the Editor: In their recent article, Larcombe and colleagues1 describe the analysis of 65 electronic cigarette fluid samples. The gas chromatography mass spectrometry method, as described in the Supporting Information, used “the ratio between the peak area corresponding to the fragment with the highest signal‐to‐noise ratio … and the peak area of the internal standard” for quantification.1 Direct comparison of the peaks for the analyte of interest and the internal standard does not take into account differences in response factor and/or ionisation efficiency for the different molecules. For accurate quantification, individual calibration curves should be prepared for all molecules of interest.