The following SPE commercial cartridges were tested: Oasis
HLB (500 mg) and Oasis MAX (150 mg) from Waters (Wexford,
Ireland), Discovery DPA-6S (500 mg), Discovery DSC-Diol (500 mg)
and Supelclean LC-SAX (200 mg) from Supelco (Bellefonte, USA),
Bond Elut Plexa (200 mg) and Bond Elut SCX (200 mg) from Agilent
(Santa Clara, USA).