The characterization of crude products from solid-phase peptide synthesis by mu-HPLC/fast atom bombardment mass spectrometry.

Crude product mixtures from the solid-phase synthesis of a series of peptides were analyzed by on-line packed, fused silica column mu-HPLC/Continuous Flow Fast Atom Bombardment Mass Spectrometry (mu-HPLC/CF-FABMS). The technique is superior to the direct FAB analysis of crude product mixtures since competitive ionization and suppression effects are not generally observed. Positive correlation between a chromatographic peak and the desired synthetic product may be obtained. An accurate assessment of peptide deprotection can be made without ambiguity arising from the MS fragmentation of the more labile t-butyl and BOC protecting groups used in FMOC-based solid-phase peptide synthesis strategies. mu-HPLC combined with in-line UV detection and MS analysis allows the use of minimum sample and injection volumes, typically 10-50 pmol contained in 0.2-0.5 microliters.

Relative bioavailability of metaproterenol in humans utilizing a single dose, stable isotope approach.

The relative bioavailability of metaproterenol (3,5-dihydroxy-alpha-[(isopropylamino)methyl]benzyl alcohol) following a single dose (10-mg metaproterenol sulfate tablet) was studied in six normal male volunteers using coadministration of a solution of a deuterated analogue (metaproterenol-d7 sulfate). The bioavailability of the tablet formulation relative to that of the oral solution was 92 +/- 9%, with excellent power at the 5% significance level. Comparison of the coadministration of the labeled and unlabeled metaproterenol sulfate solutions in two subjects after a one-week washout demonstrated the absence of an isotope effect on either absorption or elimination. A GC-MS assay for metaproterenol was developed to measure plasma concentrations resulting from oral administration. The assay was linear over the range of 0.5-8 ng/mL, corresponding to typical plasma metaproterenol concentrations obtained after a single 10-mg oral dose. Accuracy and precision data were obtained at metaproterenol concentrations of 1.0 and 2.0 ng/mL plasma to demonstrate the applicability of the assay for bioavailability studies. Following oral administration, metaproterenol showed peak plasma concentrations of 2.2 to 13 ng/mL at 0.75 to 3.0 h, with a terminal harmonic mean half-life of 2.1 h over the plasma concentration range studied. The renal clearance of 133-158 mL/min for metaproterenol slightly exceeds the glomerular filtration rate in humans.