QUANTITATIVE COMPARISONS USING GAS-CHROMATOGRAPHY MASS-SPECTROMETRY AND DUAL-ISOTOPE TECHNIQUES FOR DETECTION OF ISOTOPE AND IMPURITY INTERFERENCES

Dual-isotope methods for special quantitative comparisons using GC-MS are evaluated for assessing interferences in reaction experiments. The procedure is suitable for detecting interferences from impurities in reactants, errors due to isotope exchange and effects of kinetic diffe rences between labeled and non-labeled forms. Combined reaction of bot h isotopic forms of test compounds in the same reaction system, follow ed by concurrent pretreatment and GC-MS measurements, allow for specia l ratios to be tested statistically to determine if the interferences are significant. The comparisons may be relatively unaffected by large uncertainties in pretreatment and measurement steps and thus may yiel d greatly improved results relative to corresponding conventional asse ssments. Moreover, concentrations of the individual eluates need not b e known and eluate identifications may not be required for proper use of this approach.