Figure 9.

Separation of a mixture of phenolic acid standards in HPLC. Stationary phase—RP-18, mobile phase: water: methanol: formic acid, (75:25:0.5 v/v). Each compound is characterized by retention time in minutes (given above peaks): (1)—gallic acid (3,4,5-trihydroxybenzoic); (2)—protocatechuic acid (3,4-dihydroxybenzoic); (3)—gentisic acid (2,5-dihydroxybenzoic); (4)—vanillic acid (4-hydroxy-3-metoxybenzoic); (5)—caffeic acid (3,4-dihydroxycinnamic); (6)—syringic acid (4-hydroxy-3,5-dimetoxybenzoic); (7)—p-coumaric acid (4-hydroxycinamic); (8)—ferulic acid (4-hydroxy-3-metoxycinnamic); (9)—chlorogenic acid (depside of caffeic and quinic acids). Wavelength 254 nm.