two-dimensional liquid chromatography-tandem mass spectrometry strong-cation-exchange reversed-phase high-performance liquid chromatography atmospheric pressure chemical ionisation tandem mass spectrometry 2009-06-19T01:45:33Z SCX-RP HPLC-APCI-MS/MS A method where the sample is first subjected to two-dimensional high-performance liquid chromatography (passed through two columns in sequence –-a primary ion-exchange column where the particles show no loss or gain of charge with varying pH, and a secondary column where the stationary phase is significantly less polar than the mobile phase). The eluent is then subjected to mass spectrometry where it is ionised by interaction (electron or proton transfer) with reagent (N2, O2, H2O) gaseous ions at atmospheric pressure. The sample is analysed by two mass spectrometers in series. https://orcid.org/0000-0001-5985-7429 CHMO:0002009 SCX-RP HPLC-APCI-MS2