Direct coupling of packed column supercritical fluid chromatography to continuous corona discharge ion mobility spectrometry

In this study, packed column supercritical fluid chromatography (SFC) was directly coupled to a continuous corona discharge (CD) ion mobility spectrometer (IMS) with several modifications. The main advantage of the developed detector is its capability to introduce full column effluent up to 2000 mL min−1 CO2 gas directly into the IMS cell relative to 40 mL min−1 CO2 gas as a maximum tolerance, reported for the previous IMS detectors. This achievement was made possible because of using corona discharge instead of 63Ni as an ionization source and locating the inlet and outlet of the CO2 gas in the counter electrode of the CD in opposite direction. In addition, a heated interface was placed between back pressure regulator (BPR) and the IMS cell to heat the output of the BPR for introducing sample as the gas phase into the IMS cell. Furthermore, a make-up methanol flow was introduced between the column outlet and BPR to provide a more uniform flow through the BPR and also to prevent freezing and deposition of the analytes in the BPR. The performance of the SFC-CD-IMS was evaluated by analysis of testosterone, medroxyprogesterone, caffeine, and theophylline as test compounds and figures of merit for these compounds have been calculated.