Thermionic sodium ion source versus corona discharge in detection of alkaloids using ion mobility spectrometry

IMS spectra obtained by using a thermal ionization sodium ion (SI) source and a corona discharge (CD) source were compared in terms of resolution, selectivity and sensitivity. The reactant ion peak (RIP) for the SI source is a single narrow peak which appears in a shorter drift time compared to the main RIP of the CD ion source, (H2O)(n)H3O+. Comparison of the IMS spectra of selected alkaloids obtained with both the CD and the SI sources shows that the latter exhibits simpler pattern, including a narrow single peak for each compound, well separated from other samples peak. Furthermore, the product ion peaks (PIP) in the SI source appeared at higher drift times leading to higher peak-to-peak resolution. However, the sodium ion source is less sensitive to the selected alkaloids compared to the CD ion source.