Targeted mass spectral ratio analysis: A new tool for gas chromatography—mass spectrometry

Abstract An algorithm, referred to as targeted mass spectral ratio analysis (TMSRA) is presented whereby the ratios between intensities as a function of mass channel ( m / z ) of a target analyte mass spectrum are used to automatically determine which m / z are sufficiently pure to quantify the analyte in a sample gas chromatogram. The standard perfluorotributylamine (PFTBA) was used to evaluate the reproducibility of the collected mass spectra, which aided in selecting a mass spectral threshold for TMSRA application to a subsequent case study. Results with PFTBA suggested that a threshold of all m / z at or above 1% of the highest recorded m / z intensity should be included for targeted analysis. For the case study, 1-heptene was selected as the target analyte and n-heptane was selected as the interfering compound. These two compounds were chosen since their mass spectra are very similar. Chromatographic data containing a pure peak for these analytes were extracted, and mathematically added at various temporal offsets to generate various degrees of chromatographic resolution, R s , for the purpose of evaluating algorithm performance, and indeed, TMSRA successfully quantified 1-heptene. At the higher R s studied (0.6≤ R s ≤1.5) a deviation within±1% and a RSD generally below 1% were achieved for 1-heptene quantification. As the R s decreased, the deviation and RSD both increased. At a R s =0, a deviation of ∼9% and a RSD of∼9% were achieved.