QUANTITATIVE COMPARISONS OF REACTION-PRODUCTS USING LIQUID-CHROMATOGRAPHY WITH DUAL-LABEL RADIOACTIVITY MEASUREMENTS

Dual-label methods for radiometric measurements with liquid chromatography are evaluated. The procedures show marked improvements in data quality for comparisons of product formations and relative product abundances in multiple-pathway reaction systems. The results from these procedures are shown to be relatively unaffected by large variations in uncertainties in pretreatment steps and volume measurements. Moreover, these methods yield much better quantitative results than do commonly used corresponding conventional comparisons. These quantitative comparisons use reference substances generated by a reference reaction system as internal standards. A suite of reaction products is compared via the internal standards for components common to both reference and sample reaction systems. The dual-label methods are especially suitable for toxicologic metabolism comparisons, but could easily be adapted to other reaction systems such as syntheses or degradations. Moreover, the dual-label procedures should be amenable to non-radioactive measurements with isotope-selective methods such as mass fragmentometry, emission spectrometry or resonance methods. © 1990.