Riboflavin as a new versatile solute for the determination of OH radical rate constants by the competition kinetic technique

Abstract

Riboflavin (RF) has been used as a standard for the determination of OH radical rate constants by the competition kinetic method. In oxygenated solutions its radiolytic decomposition was found to closely correspond to G(-RF) = ( 1 2 )G OH . Its rate constant was first evaluated by employing ethanol as the standard and taking k OH+C 2H 5OH = 1.85 × 10 9 dm 3mol -1s -1. The k OH+RF value was found to be constant (= 1.2 ± 0.05 × 10 10dm 3mol -1s -1) over the pH range 1–11. Using this value the rate constant for reaction of a number of other solutes have been determined and compared with literature values. The advantages of riboflavin over other standard solutes are discussed.