A Sensitive Chemiluminescence Method for the Determination of H₂O₂ in Exhaled Breath Condensate

Abstract

In this paper, a novel flow injection chemiluminescence (FI-CL) method is proposed for the determination of picomolar L^-1 levels of hydrogen peroxide (H₂O₂) in exhaled breath condensate (EBC). This method is based on the oxidation of a low concentration of luminol (10^-7 M) by H₂O₂ at a low concentration level (< 10^-8 M) in an alkaline medium catalyzed by a complex, K₅[Cu(HIO₆)₂] (DPC), which is not interfered by other metal ions or horseradish peroxidase (HRP). Under the optimum conditions, H₂O₂ was determined over the range of 1.0 × 10^-10 to 1.0 × 10^-8 mol L^-1 with a detection limit of (3σ) of 4.1 × 10^-11 mol L^-1. The relative standard deviation (RSD) was 3.2% for 5 nmol L^-1 H₂O₂ (n = 7). The proposed method offers the advantages of ultra-sensitivity, selectivity, simplicity and rapidity for H₂O₂ determination. It was successfully applied to directly determine trace amounts of H₂O₂ (nmol L^-1) in human's EBC of both rheum and healthy volunteers. A statistically significant difference was found between patients with rheum (n = 11) and control subjects without rheum (n = 11).