Anne Joyce

A. Joyce coauthored the 1983 investigation of chain-breaking antioxidant activity in human plasma and erythrocyte membrane preparations with G. W. Burton and K. U. Ingold.^[ref] The experiment compared an inhibited autoxidation assay with high-performance liquid chromatography measurements of vitamin E, linking a functional reaction readout with a chemically selective measurement.

An original comparison shows how the two measurements can test a proposed attribution. Suppose an inhibited interval is $300\mathrm{s}$ and a calibrated radical initiation rate is $0.10\mu \mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$. Under a model of two intercepted radicals per donor molecule, the interval corresponds toIf independent chromatography instead reports $20\mu \mathrm{mol}{\mathrm{L}}^{-1}$ of the proposed donor, the activity-equivalent concentration is 75 percent of that compositional value.

This discrepancy does not uniquely identify its cause. Extraction recovery, the assumed trapping stoichiometry, accessibility within the reaction medium or an incorrect initiation rate could affect the relation. Agreement would likewise support the attribution only within the measurement model and its measurement uncertainty. The chosen numbers are not results from Joyce's paper; they explain the value of measuring composition and activity by different methods without equating either observation automatically with an effect in a living person.