A sensitive chemiluminescence method for the determination of H2O2 in exhaled breath condensate

In this paper, a novel flow injection chemiluminescence (FI-CL) method is proposed for the determination of picomolar L(-1) levels of hydrogen peroxide (H(2)O(2)) in exhaled breath condensate (EBC). This method is based on the oxidation of a low concentration of luminol (10(-7) M) by H(2)O(2) at a low concentration level (< 10(-8) M) in an alkaline medium catalyzed by a complex, K(5)[Cu(HIO(6))(2)] (DPC), which is not interfered by other metal ions or horseradish peroxidase (HRP). Under the optimum conditions, H(2)O(2) was determined over the range of 1.0 x 10(-10) to 1.0 x 10(-8) mol L(-1) with a detection limit of (3sigma) of 4.1 x 10(-11) mol L(-1). The relative standard deviation (RSD) was 3.2% for 5 nmol L(-1) H(2)O(2) (n = 7). The proposed method offers the advantages of ultra-sensitivity, selectivity, simplicity and rapidity for H(2)O(2) determination. It was successfully applied to directly determine trace amounts of H(2)O(2) (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).