On-line radiometric determination of [14C]-urapidil and its main metabolises in rat plasma, using post-column ion-pair extraction and solvent segmentation techniques

Radiochromatography in pharmaceutical and biomedical analysis

Recent advances in the chromatographic analysis of radiolabelled compounds are discussed, with emphasis on the optimization of radioactivity detection in modern chromatographic techniques. Applications are mentioned only infrequently. The state-of-the-art of common radioactivity detection methods is reviewed, as well as promising new detection principles. The latter include flow-through liquid scintillation counting of reversed-phase column eluates based on post-column extraction and solvent segmentation, flow-through heterogeneous counting using a flow cell constructed from axially aligned scintillation fibres, flow cells especially constructed for the detection of beta-emitting radioisotopes in capillary zone electrophoresis, position-sensitive analysers employed in radio planar chromatography and, finally 14C atom counting (as opposed to 14C decay counting) by accelerator mass spectrometry.

Post-column reactors for sensitive and selective detection in high-performance liquid chromatography: categorization and applications

The increasing interest in the rapid trace analysis of large series of biomedical samples using column liquid chromatographic techniques requires the use of well balanced combinations of sample pretreatment, separation and detection techniques. In such work, selectivity, sensitivity and reproducibility are the key parameters. The application of automated or semi-automated on-line pre-column technology and/or post-column reaction detection are excellent ways to meet these requirements. A critical review is presented of the theoretical background of on-line post-column reactors with emphasis on their categorization, viz., open-tubular, packed-bed, segmented-stream and hollow-fibre membrane reactors. The evaluation of these reactor systems is performed by discussing selected applications of, for instance, systems based on electrochemical and redox, hydrolytic, photochemical, ion-pairing, true chemical derivatization, peroxyoxalate chemiluminescence and solid-phase reactions. As automation is becoming even more important, a number of labelling procedures, which can be performed in an on-line pre-column mode, are briefly discussed and a comparison is made between the potential of on-line pre- and post-column procedures.