Chromatographic analysis were carried out on a LC-6A Shimadzu liquid chromatograph equipped with a SPD-6A Shimadzu UV/Vis detector. The detector signal was recorded on a Shimadzu C-R3A Chromatopac integrator. The column was a Gemini C18, 5mm, 4.6150mm with two cartridges of SecurityGuard Gemini C18, 43.0mm (Phenomenex, CA, USA).