Alkyl diol silica:: restricted access pre-column packings for fast liquid chromatography-integrated sample preparation of biological fluids

A silica-based pre-column packed with a 'restricted access material' was used for fully automated solid-phase extraction of drugs and metabolites from untreated biological fluids via a simple valve-switching method. The bifunctional sorbent employed, alkyl diol silica, is characterised by a different chemical modification of the outer surface (diol groups) and the pore surface of the particles (alkyl chains: C-4, C-8 or C-18). This allows for a fast and efficient clean-up of complex biological samples, such as blood, serum, urine or milk, with exclusion of the macromolecular matrix (proteins, nucleic acids) in less than 1.5 min. (C) 2001 Elsevier Science B.V. All rights reserved.