article priority journal Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization chemistry unclassified drug Mass spectrometry mass spectrometry matrix assisted laser desorption ionization time of flight mass spectrometry carbohydrate analysis chemical structure Química Spectrometry, Mass, Electrospray Ionization gentisic acid nonhuman Carbohydrates harman Ultraviolet Rays controlled study electrospray mass spectrometry harmine photochemistry ultraviolet radiation Fluorescence Harmine chemical reaction metabolism ultraviolet spectrophotometry Ciencias Exactas Desorption Electrospray ionization