Figure 6 Reaction of OPA with a primary amine and a thiol. (From Ref. 132.)

OPA has shown potential as a derivatization agent for glutathione (γ-GluCys-Gly) determination using electrochemical detection at glassy carbon electrodes [137]. The derivatization reaction is fast (complete in 10 s) as the thiol required to form the electroactive derivative is part of the analyte molecule. The peak potential of the resulting product is pH dependent in the pH 8-11 range. Using this methodology, glutathione derivatives were analyzed and detection limits around 40 pmol (0.67 µM) were achieved at +0.80 V versus. Ag/AgCl.