Keywords: Metformin-HCl (C4H11N5.HCl); Phenformin (C10H15N5.HCl); Insulin (C267H404N72O78S6); Guanidine hydrochloride (NH2C(=NH)NH2 · HCl); Galegine analogue (2-methylthio-2-imidazoline hydroiodide, C4H8N2S·HI); Arginine (C6H14N4O2); Urea (CH4N2O); Food analysis;