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