This CEN Technical Report specifies a method for the determination of the mass of water soluble NO3-, SO42-, Cl-, NH4+, Na+, K+, Mg2+, Ca2+ in PM2,5 samples which can be used to comply with Directive 2008/50/EC. This CEN Technical Report describes a measurement method which comprises sampling of anions and cations as part of the PM2,5 particulate phase, sample extraction and analysis of anions and cations by ion chromatography. Alternately, cations, excluding ammonium can be analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). This CEN Technical Report may be used at rural background monitoring sites that are in accordance with the requirements of Directive 2008/50/EC. However, since this CEN Technical Report has not been validated in the field for these, or any other, monitoring site types, it may be considered equally applicable to all site types. NOTE The detection limits described in this CEN technical report method will be limited by the noise level of the detector and the variability of the mass in laboratory blank filters rather than by the concentrations of anions and cations in ambient air.