The sorbent used in the application of solid-phase extraction (SPE) for the treatment of water samples was Oasis HLB,
a copolymer of poly(divinil-benzene-co-N-vinylpryrrolidone
(200mg, 6mL) (Waters, Milford, MA, USA). For cleanup purposes in the case of the treatment of vegetable samples
Alumina N homemade cartridge (1.5g) obtained from Supelco
was used.