Integration of ion-exchange chromatography fractionation with reversed-phase liquid chromatography-atmospheric pressure chemical ionization mass spectrometer and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for isolation and identification of compounds in Psoralea corylifolia - Chen, X; Kong, L; Su, X; Pan, C; Ye, M; Zou, H (J Chromatogr A, 2005)