Coupling of column liquid chromatography and thermospray mass spectrometry via phase-system switching with an ion-exchange trapping column

Abstract

A benzenesulphonic acid-type cation exchanger (pKa < 1) is used as trapping-column material in a phase-system switching for the on-line coupling of column liquid chromatography and thermospray mass spectrometry. Phase-system switching is used to remove non-volatile constituents from the mobile phase, so that eluents containing non-volatile buffers and ion-pairing agents can be used without contaminating the mass spectrometer. The total analytical system is optimized using four benzalkonium test compounds (quaternary ammonium compounds). The reversed-phase separation of the test compounds as well as the parameters involved in the sorption on and desorption from the trapping column are studied. Important parameters during sorption are the concentration of the phosphate buffer and the percentage of acetonitrile in the mobile phase. During desorption of the test compounds from the ion-exchanger the percentage of acetonitrile in the desorption eluent and the pH are the most important factors. As an example, the analysis of domiphen in nasal drops is shown.