In order to investigate the recycling of the TEPA-MP, all the TEPA-MP used for dSPE cleanup procedure were collected and soaked in sodium hydroxide solution at a concentration of 1.0 mol/L for at least 0.5 h, and then were washed with water and methanol to remove the redundant sodium hydroxide until the eluent pH value was about 7.0. Finally, the TEPA-MP was separated and dried under a vacuum at 60 °C for 12 h and reused for dSPE