Gas Chromatography–Atmospheric Pressure Photoionization Mass Spectrometry: Detection of Unknown Low-Molecular-Weight Organic Components of Complex Mixtures at the Trace Level

The limit of detection of gas chromatography–electron ionization mass spectrometry (in scanning in the full ion current mode) is 10–11 to 10–10 g, depending on the substance. A full electron ionization mass spectrum of a substance can be recorded for 10–10 to 10–9 g, while the peak of the molecular ion in these mass spectra is often either absent or of low intensity. The minimum amount of a substance that can be detected by gas chromatography–atmospheric pressure photoionization mass spectrometry is 10–12 to 10–10 g and by gas chromatography–atmospheric pressure photochemical ionization mass spectrometry is 10–14 to 10–12 g, depending on the analyte and the reagent substance. For the amount of substance in the range from 10–9 to 10–10 g and up to the limit of detection, a mass spectrum consisting of the peaks of the M+ ^∙ or MH+ ion or both of them is recorded. It gives selective information about the molecular weight of the analyte throughout the studied range. Identifying trace amounts of unknown components in complex mixtures can be achieved by sharing data from the mass spectra of electron ionization and atmospheric pressure photoionization.