An integrated approach for the chemical characterization and oxidative potential assessment of indoor PM 2.5 Victor G. Mihucz a,b, ⁎, Tamás Szigeti a,b , Christina Dunster c , Martina Giannoni d , Yvonne de Kluizenaar e , Andrea Cattaneo f , Corinne Mandin g , John G. Bartzis h , Franco Lucarelli d , Frank J. Kelly c , Gyula Záray a,b a Cooperative Research Centre for Environmental Sciences, Eötvös Loránd University, H-1117 Pázmány Péter stny 1/A, Budapest, Hungary b Hungarian Satellite Trace Elements Institute to UNESCO, H-1117 Pázmány Péter stny 1/A, Budapest, Hungary c MRC-PHE Centre for Environment and Health, King's College London, SE1 9NH London, UK d Department of Physics and Astronomy, University of Florence and INFN, 50019 Sesto Fiorentino, Italy e Urban Environment and Safety, The Netherlands Organization for Applied Scientific Research (TNO), P.O. Box 49, 2600 AA, Delft, The Netherlands f Department of Science and High Technology, University of Insubria, 22100 Como, Italy g CSTB — Centre Scientifique et Technique du Bâtiment, Université Paris Est, 84 avenue Jean Jaurès, 77447 Marne-la-Vallée Cedex 2, France h Department of Mechanical Engineering, University of West Macedonia, Sialvera & Bakola Str., Kozani, West Macedonia T. K. 50100, Greece abstract article info Article history: Received 13 October 2014 Accepted 19 October 2014 Available online 24 October 2014 Keywords: Elemental/organic carbon Occupational exposure Antioxidant depletion Particulate matter Trace elements Inorganic ions An integrated approach has been developed for the multi-component analysis of indoor PM 2.5 collected onto the same quartz fiber filter (QFF) by using an innovative combination of techniques such as inductively coupled sec- tor field plasma mass spectrometry (ICP-SF-MS) with vapor-phase microwave-assisted aqua regia or sonication- assisted water extraction, ion chromatography, thermal–optical transmittance as well as high performance liquid chromatography and enzyme-linked 5,5′-dithio-bis(2-nitrobenzoic acid) assay for the determination of elemen- tal composition, major inorganic ions, elemental/organic carbon (EC/OC) as well as oxidative potential (OP) through ascorbate (AA) and reduced glutathione (GSH) depletion, respectively. The low mass of PM 2.5 collectable indoors, the elemental blank values of the QFFs and the sample volume/acidity requirements of the ICP-SF-MS represented a challenge for elemental determination. Finally, this approach was successfully applied for determi- nation of 15 elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn and Pb) at the ng m -3 level in more than two-thirds of indoor PM 2.5 (n = 25) collected in mechanically ventilated offices within the European Union pro- ject OFFICAIR at increased sampling flow rates (0.6 m 3 h -1 –2.3 m 3 h -1 ) and sampling time (cca. 100 h) in the acidic/aqueous extracts. The concentration of Cl - , NO 3 - , SO 4 2- , Na + , NH 4 + ,K + , Ca 2+ , Mg 2+ , OC and EC was at the μgm -3 level in the aqueous extracts. This new approach aiming at the comprehensive characterization of low mass indoor PM 2.5 samples allowed assessment of OP AA and OP GSH in all samples. The PM 2.5 critical sample mass to achieve elemental determination was approximately 400 μg. © 2014 Elsevier B.V. All rights reserved. 1. Introduction In the past decade, the number of chemical studies aiming at under- standing the adverse effects of exposure to atmospheric particulate matter (PM) with an aerodynamic diameter smaller than 2.5 μm (PM 2.5 ) on human health at workplaces has increased substantially [1–15], since people living in urban areas spend more than 90% of their time indoors [16]. Only some of these reports have, however, dealt with indoor air quality in offices located in mechanically ventilated buildings [1,3,4,11–14]. Given the increased use of forced ventilation in modern office blocks, a better understanding of air quality in these en- vironments is required. Airborne PM is a complex and heterogeneous matrix containing minerals, salts, organic matter and elemental carbon (EC). The organic fraction is composed of many chemical compounds, rendering the com- plete characterization of typically collected small masses of PM ex- tremely difficult. Airborne PM has been associated with adverse health effects such as respiratory disease and cardiovascular diseases [17–19]. The smaller particles have been hypothesized to be more harmful since they penetrate deeper into the respiratory system. Less is known about which constituents of PM 2.5 are primarily responsible for the adverse health effects [20–22]. Therefore, there is a strong need for innovative approaches for multi-component analysis of PM 2.5 by harmonizing existing sampling strategies involving collection of PM onto filters with instrumental analytical techniques – each with their own strengths and limitations – aiming at a better understanding Microchemical Journal 119 (2015) 22–29 ⁎ Corresponding author at: Cooperative Research Centre for Environmental Sciences, Eötvös Loránd University, H-1117 Pázmány Péter stny 1/A, Budapest, Hungary. Tel.: +36 1 372 2500/ext.1227; fax: +36 1 372 2608. E-mail address: vigami72@yahoo.es (V.G. Mihucz). http://dx.doi.org/10.1016/j.microc.2014.10.006 0026-265X/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc