The MIP-SPE cartridges had been previously conditioned with 3 mL of MeOH, 3 mL of MeCN, and 3 mL of water. After the loading step, the sorbents were cleaned up with water and MeCN/water (40:60 v/v). Next, the sorbents were completely dried and further washed with MeCN and MeOH/MeCN (10:90 v/v). After elution, the eluates were evaporated to dryness and the residues were reconstructed in 500 μL of a MeOH/water (50:50 v/v) solution for LC−MS analysis.