Page 274 - Multidimensional Chromatography

Biomedical and Pharmaceutical Applications 269

Figure 11.6 (a) Schematic illustration of a restricted-access sorbent particle. (b) On-line
SPE–LC–MS using an alkyl-diol RAM pre-column for the determination of cortisol, corti-
sone, prednisolone and fludrocortisone (100 ng/ml each) in untreated plasma. Part (a)
reprinted from Journal of Chromatography, A 797, J. Hermansson et al., ‘Direct injection of
large volumes of plasma/serum of a new biocompatible extraction column for the determi-
nation of atenolol, propanolol and ibuprofen. Mechanisms for the improvement of chromato-
graphic performance,’ pp 251–263, copyright 1998, with permission from Elsevier Science.
Part (b) reprinted from Journal of Chromatography, A 762, R. A. M. van der Hoeven et al.,
‘Liquid chromatography–mass spectrometry with on-line solid-phase extraction by a
restricted-access C 18 precolumn for direct plasma and urine injection,’pp. 193–200, copyright
1997, with permission from Elsevier Science.

relatively large volumes (200–500 l) of plasma and serum. By using these pre-
columns in an on-line SPE–LC set-up with fluorescence detection, Hermansson
et al. (96) could quantitatively determine atenolol and propanolol in serum down to
the low ng/ml level. The stability and performance of the system was good, even