Hydrogen peroxide assessment in exhaled breath condensate: Condensing equipment-rapid flow injection chemiluminescence method

Abstract

Several biomolecules in Exhaled Breath Condensate (EBC) can be used as breath biomarkers providing useful clinical information concerning inflammatory lung diseases. Hydrogen peroxide has a special place among biomarkers as it can be directly linked to oxidative stress built up in the human body. Methods for hydrogen peroxide in EBC are essential for a vast number of studies spanning from basic studies to disease diagnosis. Methods currently in use are not automated, time-consuming and tedious. Moreover, most condensing equipment in use is not portable. To address these, we developed portable condensing equipment as an extra alternative and a fully automated Flow Injection (FI) - Chemiluminescence method for hydrogen peroxide determination. The proposed condensing equipment provides collection efficiency better than 86% allowing the collection of 2-3 mL sample in 20 min. The method involves mixing a luminol solution stream that is used as sample carrier with a cobalt(II) stream. Reaction of EBC with luminol in the presence of cobalt(II) catalyst produces light proportional to hydrogen peroxide concentration. The automated FI method features a 10 nmol L-1 detection limit and good linearity (r=0.997). Precision and recoveries are better than 6.0% RSD and 64.9%, respectively. Comparison with the, commonly used for EBC, manual fluorimetric method showed no significant difference, P > 0.001, while correlation of the methods is high, r=0.94. The method provides automation in sample handling, sample throughput of 180 samples h-1 and low detection limit. ©2007 Sociedade Brasileira de Química.