Insight Into Halogen Chemistry and Indoor Air Quality Using Iodide CI-TOFMS

Indoor Air Quality CI-TOFMS

Observations and Impacts of Bleach Washing on Indoor Chlorine Chemistry 

Wong et al. 
DOI: 10.1111/ina.12402
Indoor Air, 2017 

Bleach cleaning solutions used indoors can produce gaseous chlorine (Cl2) and hypochlorous acid (HOCl),  along with other species that aggressively react with organic molecules on and in human skin, indoor surfaces, water, and fine particles. The precursors and products of these reactions are frequently encountered by people indoors, but their identities and behavior were not well characterized.  

A team of researchers from Georgia Tech, the University of York, Caltech and the University of Toronto used a chemical ionization time-of-flight mass spectrometer equipped with an iodide reagent ion source (CI-TOFMS) to detect and identify the chlorine-containing molecules created when cleaning a room with a commercial bleach solution. The instrument was operated with a resolution of 3000 (m/dm FWHM) and compounds were identified on the basis of their high-resolution exact mass-to-charge ratios and isotope patterns. They additionally used an aerosol time-of-flight mass spectrometer (CTOF-AMS) to characterize aerosol in the room. 

Chlorine-containing compounds identified as part of the study included gaseous chlorine (Cl2), hypochlorous acid (HOCl), nitryl chloride (ClNO2), dichlorine monoxide (Cl2O), and chloramines (NHCl2, NCl3). Additionally, ClO was detected, which may indicate either the ClO radical itself, or the presence of larger chlorine-containing molecules.  

Significant concentrations of chlorine-containing species are immediately created by cleaning with bleach. In particular, hundreds of ppbs of HOCl were observed. Chlorine-containing aerosol also increased. The researchers found evidence for reaction with surfaces other than the surface that was cleaned, indicating that bleach cleaning may affect all objects and surfaces in the room where it is used. The authors concluded that the high concentrations of chlorine-containing species were unexpected, and that bleach washing may contribute to surface and gas-phase oxidation.  

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