Optimization of Critical Parameters in Chiral Analysis of Prothioconazole by Supercritical-Fluid Chromatography-Mass Spectrometry

This chapter highlights attempts to understand the key variables for separation and subsequent ionization of the chiral molecules prothioconazole and prothioconazole-desthio by supercritical-fluid chromatography-mass spectrometry (SFC-MS). The addition of water as a proton donor was investigated and found to be a critical parameter in ionization via electrospray ionization (ESI) under certain separation conditions. Also, the optimal mode and polarity for ionization of prothioconazole and prothioconazole-desthio were investigated, finding that optimal ionization conditions can vary greatly between reversed-phase liquid chromatography (RPLC) and SFC. The best ion polarity for ionization of prothioconazole reversed from positive ion polarity in RPLC to negative ion polarity when analyzed by SFC. The limit of quantitation for these molecules using different chromatographic techniques was also investigated. A sixfold increase in sensitivity was observed for prothioconazole-desthio in SFC versus RPLC, indicating certain molecules may be ideal for analysis by SFC when sensitivity is a critical parameter. © 2019 American Chemical Society.