RESUMEN
Objective: To establish a determination method for free salicylic acid in paracetamol, caffeine and aspirin powder by HPLC.Methods: The column was Welch Ultimate(C) C 18 (250 mm× 4.6 mm , 5 μm), the mobile phase was acetonitrile-tetrahydrofuran-glacial acetic acid-water(22∶5∶5∶68), the detection wavelength was 303 nm, and the flow was 1.0 ml·min-1.Results: The linear range of hydrochloride was 1.500-75.000 μg·ml-1 (r=0.999 9), the average recovery was 99.12% with RSD of 0.75% (n =9),and the detection limit was 1.5 ng (S/N =3).Conclusion: The method is simple, the result is accurate with higher sensitivity and the better reproducibility, which can be used for the determination of free salicylic acid in paracetamol, caffeine and aspirin powder.