The sample (3.0 g of liver, kidney, lung, muscle, thyroid or 3 mL of plasma or milk) is placed in a 16 x 100 mm glass tube with Teflon-coated screw caps. After preheating for 1 min in a 85 °C water-bath, 4 mL of boiling phosphate buffer are added. Then, 500 µL of the aqueous solution of internal standard is added. The scattering of the blended matrices is achieved by vigorous manual shaking. The extract is kept in the water-bath for 10 min and stirred periodically with Vortex, then cooled and centrifuged at 1000 x g for 10 min. The supernatant is transferred to a 15 x 100 mm test tube. The extraction is repeated twice with 3 mL of phosphate buffer.

Column conditioning: The SPE cartridges are solvated with 3 mL of methanol and 2 mL of acetonitrile, then washed with 20 mL of distilled water with special care in order to prevent any air from entering.

Sample application: The solution to be purified (about 10 mL) is placed in the cartridge reservoir and then percolated.

Column washing: The phase is rinsed with 2 mL of distilled water to eliminate most of the polluting substances and dried under aspiration for 1 min.

Elution: 2 mL methanol / acetonitrile (50:50, v/v)

Evaporation: The eluate is placed in a 10 mL conic flask and then evaporated to dryness with a rotating evaporator under vacuum (40 °C).