GAS CHROMATOGRAPHY-ATOMIC EMISSION DETECTION FOR THE MEASUREMENT OF ISOTOPES - APPLICATION TO BIOEQUIVALENCE STUDIES

This study was designed to demonstrate the ability of gas chromatograp hy-atomic emission detection (GC-AED) to quantitatively measure amount s of labeled and unlabeled molecules when they are mixed together with both variable overall concentrations (labeled+unlabeled) and variable isotope ratios. To perform this study, simulations of bioequivalence trials were carried out using C-13 stable isotopically labeled molecul es (SIL) coadministered with the unlabeled drug to act as biological i nternal standards. Various methodological approaches are shown and dif ferent methods of calculation developed for the quantitative determina tion of both SIL and unlabeled molecules. The pharmacokinetic paramete rs experimentally obtained are quite in accordance with the target val ues and GC-AED appears to be a valuable alternative to mass spectromet ry for this kind of trial with concomitant use of labeled and unlabele d molecules.