Determination of raclopride in human plasma by on-column focusing packed capillary liquid chromatography-electrospray ionisation mass spectrometry.

A packed capillary liquid chromatography-electrospray ionisation mass spectrometry method was developed for the quantitative determination of raclopride in human plasma samples. Plasma samples containing the drug and its isotopically substituted analogue (2H3)raclopride as internal standard were extracted on solid-phase extraction discs, evaporated and reconstituted in a solvent with less elution strength than the mobile phase. Packed capillary columns of 100 mm x 500 microm I.D. were used to obtain high mass sensitivity in the analysis and large volume injections (20 microl) were performed with analyte enrichment on top of the column. The assay exhibited satisfactory accuracy and precision over the concentration range of 0.2-15 nM (70-5200 pg/ml) with a limit of quantification of 0.2 nM. Raclopride in plasma was determined after intravenous injection in a positron emission tomography study performed in the tracer dose range.