On-line SPE-RP-LC for the determination of insulin derivatives in biological matrices

An automated and on-line solid-phase extraction (SPE)-liquid chromatography (LC) procedure is described for the determination of insulin in biological matrices. The total procedure consists of two SPEs in series, followed by RP-LC separation. During the first SPE a strong anion-exchange (SAX) cartridge (ISOLUTE, 40-90 mum, 10 x 4 mm i.d.) is used, followed by a RP-cartridge (Luna C-8, 4 x 2.0 mm W.). The second SPE cartridge contains the same material as the LC column and is used to transfer the sample from the SAX cartridge to the LC column. The developed system can detect 100 nmol/l insulin in aqueous samples and 200 nmol/l insulin in spiked plasma samples using UV. When electrospray ionization (ESI)-mass spectrometry (MS), was coupled with the developed system, the LODs were lowered by a factor two to 50 and 100 nmol/l for aqueous and spiked plasma samples, respectively. (C) 2003 Published by Elsevier Science B.V.