High performance liquid chromatography/electrospray ionization mass spectrometry for simultaneous analysis of alkylamides and caffeic acid derivatives from Echinacea purpurea extracts - Cech,N.B.; Eleazer,M.S.; Shoffner,L.T.; Davis,A.C.; Crosswhite,M.R.; Mortenson,A.M. (J Chromatogr A, 2006)