Antonius T. M. Van Kessel

Antonius T. M. Van Kessel coauthored the visible-light co-oxidation assay with Evan A. Haidasz and Derek A. Pratt for characterizing radical-trapping antioxidants.^[ref] A central analytical distinction is between reaction speed and finite trapping capacity: an inhibitor can intercept radicals rapidly yet be exhausted after relatively few events.

An original competition model holds the concentrations of donor and reporter approximately constant over a short interval. Let the effective rates for a radical be $a=k_A{c}_A$ for interception and $b$ for a competing reporter route. The probability of interception as the first event isChoosing $a=10{\mathrm{s}}^{-1}$ and $b=2{\mathrm{s}}^{-1}$ gives $f_A=5/6$. Halving $k_A$ without changing concentration gives $f_A=5/7$. The kinetic response changes even if the two preparations have the same total number of donor molecules.

Under a separate ideal capacity model, two intercepted radicals per donor at $c_A=10\mu \mathrm{mol}{\mathrm{L}}^{-1}$ and constant initiation rate $R_i=0.10\mu \mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$ give an inhibited interval $2c_A/R_i=200\mathrm{s}$. That capacity estimate alone does not distinguish the two chosen rate constants. Actual co-oxidation traces require the appropriate chain-reaction and reporter model; the simple competition and capacity calculations illustrate different kinds of information, not individual experimental tasks attributed to Van Kessel.