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.

Determination of specific radioactivity for (76)Br-labeled compounds measuring the ratio between (76)Br and (79)Br using packed capillary liquid chromatography mass spectrometry.

Packed capillary liquid chromatography with electrospray mass spectrometry was used for direct determination of the specific radioactivity by calculation of isotope ratios between the (76)Br- and (79)Br-labeled analogues of N-((3-aminomethyl)benzyl)-4-bromobenzamide. Using 20 microL injections on packed capillary columns, sufficient mass sensitivity was attained for the determination on an injected amount of radioactivity corresponding to approximately 2 MBq (0.3 pmol of the (76)Br isotopic analogue).

Reversed-phase ion-pair chromatography coupled to electrospray ionisation mass spectrometry by on-line removal of the counter-ions.

A strong anion-exchanger was used as a trapping column to perform on-line coupling of ion-pair chromatography with electrospray ionisation mass spectrometry. Ion-pairing reagents were used to retain polar analytes of low molecular mass away from the solvent front in reversed-phase LC. The trapping column enabled removal of the non-volatile counter-ions from the mobile phase prior to detection, so that the electrospray process could be performed with favourable ionisation conditions and without contamination of the interface. The efficiency of the trapping process was studied for 1-octanesulfonic acid and sodium dodecyl sulfate as ion-pairing reagents. Using this on-line trapping method, biopterin and guanidine could be retained with a k'>2 and detected by electrospray mass spectrometry with a stable signal.

Compounds labelled with short-lived beta(+)-emitting radionuclides and some applications in life sciences. The importance of time as a parameter.

Some examples of recent development of the synthesis of compounds labelled with short-lived beta(+)-emitting radionuclides will be discussed with an emphasis on the importance of time in selecting a synthetic strategy. Furthermore the use of such labelled compounds to monitor certain processes in areas within the field of analytical chemistry and in various applications in drug development will be presented.