An efficient and reproducible method for measuring hydrogen peroxide in exhaled breath condensate

We investigated the sensitivity and reproducibility of a test procedure for measuring hydrogen peroxide (H 2 O 2 ) in exhaled breath condensate and the effect of storage of the condensate on the H 2 O 2 concentration, and compared the results to previous studies. Twenty stable COPD patients breathed into our collecting device twice for a period of 10 min. The total exhaled air volume (EAV) and condensate volume were measured both times and the H 2 O 2 concentration of the condensate was determined fluorimetrically. The concentration was measured again after freezing the reaction product at −70°C for a period of 10, 20 and 40 days. We collected 2–5 ml condensate in 10 min. The EAV and condensate volumes were strongly correlated. There was no significant difference between the mean H 2 O 2 concentration of the first and second test. We obtained a detection limit for the H 2 O 2 concentration of 0·02 μ moll −1 . The H 2 O 2 concentration appeared to remain stable for a period up to 40 days of freezing. Compared to previous studies we developed a more efficient breath condensate collecting device and obtained a lower H 2 O 2 detection limit. The measurement of exhaled H 2 O 2 was reproducible. In addition, storage of the samples up to 40 days showed no changes in H 2 O 2 concentration.