Quantitative detection of hydrogen peroxide in rain, air, exhaled breath, and biological fluids by NMR spectroscopy

Hydrogen peroxide (H(2)O(2)) plays a key role in environmental chemistry, biology, and medicine. H(2)O(2) concentrations typically are 6 to 10 orders of magnitude lower than that of water, making its quantitative detection challenging. We demonstrate that optimized NMR spectroscopy allows direct, interference-free, quantitative measurements of H(2)O(2) down to submicromolar levels in a wide range of fluids, ranging from exhaled breath and air condensate to rain, blood, urine, and saliva. NMR measurements confirm the previously reported spontaneous generation of H(2)O(2) in microdroplets that form when condensing water vapor on a hydrophobic surface, which can interfere with atmospheric H(2)O(2) measurements. Its antimicrobial activity and strong seasonal variation speculatively could be linked to the seasonality of respiratory viral diseases.