title: Detection and quantification of reactive oxygen species (ROS) in indoor air.
abstract: Reactive oxygen species (ROS), such as free radicals and peroxides, are environmental trace pollutants potentially associated with asthma and airways inflammation. These compounds are often not detected in indoor air due to sampling and analytical limitations. This study developed and validated an experimental method to sample, identify and quantify ROS in indoor air using fluorescent probes. Tests were carried out simultaneously using three different probes: 2',7'-dichlorofluorescin (DCFH) to detect a broad range of ROS, Amplex ultra Red® (AuR) to detect peroxides, and terephthalic acid (TPA) to detect hydroxyl radicals (HO(•)). For each test, air samples were collected using two impingers in series kept in an ice bath, containing each 10 mL of 50 mM phosphate buffer at pH 7.2. In tests with TPA, that probe was also added to the buffer prior to sampling; in the other two tests, probes and additional reactants were added immediately after sampling. The concentration of fluorescent byproducts was determined fluorometrically. Calibration curves were developed by reacting DCFH and AuR with known amounts of H2O2, and using known amounts of 2-hydroxyterephthalic acid (HTPA) for TPA. Low detection limits (9-13 nM) and quantification limits (18-22 nM) were determined for all three probes, which presented a linear response in the range 10-500 nM for AuR and TPA, and 100-2000 nM for DCFH. High collection efficiency (CE) and recovery efficiency (RE) were observed for DCFH (CE=RE=100%) and AuR (CE=100%; RE=73%) by sampling from a laboratory-developed gas phase H2O2 generator. Interference of co-occurring ozone was evaluated and quantified for the three probes by sampling from the outlet of an ozone generator. The method was demonstrated by sampling air emitted by two portable air cleaners: a strong ozone generator (AC1) and a plasma generator (AC2). High ozone levels emitted by AC1 did not allow for simultaneous determination of ROS levels due to high background levels associated with ozone decomposition in the buffer. However, emitted ROS were quantified at the outlet of AC2 using two of the three probes. With AuR, the concentration of peroxides in air emitted by the air cleaner was 300 ppt of H2O2 equivalents. With TPA, the HO(•) concentration was 47 ppt. This method is best suited to quantify ROS in the presence of low ozone levels.
authors: Comisión Nacional de Energía Atómica, Avenida Gral. Paz 1499, 1650 San Martín, Provincia de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Avenida Rivadavia 1917, 1033 Ciudad Autónoma de Buenos Aires, Argentina; Universidad de Buenos Aires, FCEN, INQUIMAE, DQIAQF, Ciudad Universitaria Pabellón II, 1428 Ciudad Autónoma de Buenos Aires, Argentina.
authors: V Nahuel
authors: VN
authors: Montesinos
authors: Lawrence Berkeley National Laboratory, Indoor Environment Group, 1 Cyclotron Road MS 70-108B, Berkeley, CA, USA; Clermont Université, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France; CNRS, UMR 6296, ICCF, BP 80026, F-63177 Aubière, France.
authors: Mohamad
authors: M
authors: Sleiman
authors: Lawrence Berkeley National Laboratory, Indoor Environment Group, 1 Cyclotron Road MS 70-108B, Berkeley, CA, USA.
authors: Sebastian
authors: S
authors: Cohn
authors: Comisión Nacional de Energía Atómica, Avenida Gral. Paz 1499, 1650 San Martín, Provincia de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Avenida Rivadavia 1917, 1033 Ciudad Autónoma de Buenos Aires, Argentina; Universidad de General San Martín, Instituto de Investigación e Ingeniería Ambiental, Peatonal Belgrano 3563, 1650 San Martín, Pcia. Buenos Aires, Argentina.
authors: Marta I
authors: MI
authors: Litter
authors: Lawrence Berkeley National Laboratory, Indoor Environment Group, 1 Cyclotron Road MS 70-108B, Berkeley, CA, USA. Electronic address: HDestaillats@lbl.gov.
authors: Hugo
authors: H
authors: Destaillats
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D005452:Fluoresceins / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D057230:Limit of Detection; D010126:Ozone / Q000032:analysis*; D010795:Phthalic Acids / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000032:analysis*
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D010795:Phthalic Acids; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; C037631:2',7'-dichlorofluorescein; C406866:2-hydroxyterephthalic acid; D010126:Ozone; D006861:Hydrogen Peroxide
keywords: Hydrogen peroxide; Hydroxyl radical; Plasma air cleaner; Reactive oxygen species (ROS)