You should use reverse phase chromatography to separate the local anesthetic hexylresorcinol and the blood thinner warafin in the same sample (see the structure of the analytes below). As a stationary phase, you have a C18 column, and the mobile phase you use is an 80:20 mixture of 0.1 M phosphate buffer (pH 3): methanol. . CH3 Hexylresorcinol, pKa = 9.55, logP= 3.77 :0 Warfarin, pka = 5.87, logP= 2.70