Abstract Several sets of reference air filters were pre- pared as part of an IAEA evaluation of the performance of laboratories involved in air-pollution studies. Each set comprised three polycarbonate membrane filters, two of which were loaded with urban air particulate matter (APM) obtained in Vienna or Prague, and one unloaded filter. The filters were loaded by filtration of a suspension of the APM materials in water. The homogeneity both of bulk APM materials and of the loaded filters was evalu- ated and found suitable by determining several elements by instrumental neutron-activation analysis (INAA), pro- ton-induced X-ray emission (PIXE), and micro-X-ray en- ergy-dispersive fluorescence analysis (μ-EDXRF). After evaluation of the homogeneity, INAA, PIXE, EDXRF, atomic absorption spectrometry (AAS), inductively cou- pled plasma optical emission spectrometry (ICP–OES), and ICP mass spectrometry (ICP–MS) were used to char- acterize the filter materials and establish “target values” and their associated standard deviations for 15 elements. Problems encountered during the preparation of these unique, simulated air filters and the criteria for setting both the target values and standard deviations are pre- sented. Introduction The unavailability of appropriate air filter reference mate- rials (RMs) for air pollution studies [1–3] has been one of the main reasons for the lack of progress in implementa- tion of quality-control measures in this field. The charac- teristics of the ideal RM containing airborne particulate matter (APM) loaded onto a filter have recently been summarized by Heller-Zeisler et al. [2]. In addition to these, the particle-size distribution and the thickness of the deposit should also match those of real aerosol sam- ples because these samples are frequently assayed by PIXE and XRF analytical techniques whose accuracy, es- pecially in PIXE analysis [4], is strongly influenced by these latter factors. For approximately four years, the International Atomic Energy Agency (IAEA) has been developing simulated APM filters, in limited quantities, for quality-control pur- poses in air pollution studies – in particular to meet the needs of those laboratories employing nuclear and nu- clear-related techniques [2, 6, 7]. The goal of this work was to prepare two sets of different reference air filters in a greater number, according to a recently published proce- dure [2], with each set consisting of approximately 250 poly- carbonate (Nuclepore, Costar) membrane filters – one loaded with an APM from Vienna, the second with an APM from Prague. The set also contains one filter (herein referred to as a “blank” for convenience) which was used as received from the supplier. These sets of filters were in- tended to be used in a proficiency test to evaluate the per- formance of those laboratories involved in on-going air pollution studies organized by the IAEA [6, 7] and if suf- ficient sets remain, for a world-wide intercomparison ex- ercise. Although these first two sets have a larger varia- tion in element content than would be considered desir- able for an RM, with some modification and improvement in the preparation procedure, the modified approach might be employed, if found suitable, for the preparation of an RM set. Materials and methods APM materials. The Vienna (Austria) APM material (herein re- ferred to as the “Vienna APM”) was obtained from the air intake ducts of the Vienna General Hospital on three separate occasions during the periods September 1994 to December 1995. The three batches were processed at the IAEA Laboratories in Seibersdorf J. Kučera · B. Smodiš · K. Burns · P. De Regge · M. Campbell · V. Havránek · M. Makarewicz · A. Toervenyi · E. Zeiller Preparation and characterization of a set of IAEA reference air filters for quality control in air-pollution studies Fresenius J Anal Chem (2001) 370 : 229–233 © Springer-Verlag 2001 Received: 26 October 2000 / Revised: 8 January 2001 / Accepted: 10 January 2001 SPECIAL ISSUE PAPER J. Kučera () · V. Havránek Nuclear Physics Institute, 250 68 Řež, near Prague, Czech Republic e-mail: kucera@ujf.cas.cz B. Smodiš · K. Burns · P. De Regge · M. Campbell · M. Makarewicz · A. Toervenyi · E. Zeiller International Atomic Energy Agency, Wagramer Strasse 5, 1400 Vienna, Austria