APPLICATION OF ο -TOLIDINE AS SUBSTRATE FOR THE ELECTROCHEMICAL DETERMINATION OF HEMOGLOBIN OR HYDROGEN PEROXIDE

Abstract

In this paper hemoglobin (Hb) was used to catalyze the oxidative reaction of o-tolidine (OT) with H 2 O 2. The oxidative product of OT with H 2 O 2 was an azo substrate, which was electroactive and had a sensitive linear sweep voltammetric reductive peak at-0.52 V (vs. SCE) on hanging mercury drop working electrode (HMDE) in pH 5.0 Britton-Robinson (B-R) solution. The conditions of Hb catalytic reaction and voltammetric detection were optimized. Under the optimal conditions, the electrochemical behaviour of the oxidative product was carefully investigated and the electrode process of the product on mercury electrode was proposed. Based on the increase of the reductive peak current of the oxidative product with the concentration of the H 2 O 2 or Hb, a new electrochemical method for the determination of trace amount of H 2 O 2 or Hb was proposed. The calibration graph had a linear range of 6.0 x 10-8 to 4.0 x 10-5 M for H 2 O 2 and 1.0 x 10-9 to 7.0 x 10-7 M for Hb with the detection limit of 1.0 x 10-8 M H 2 O 2 and 5.0 x 10-10 M Hb (3σ), respectively. This new proposed method was further attempted to determine the content of H 2 O 2 in fresh rainwater with satisfactory results.