In this work, a methodology for estimating the concentration of ions present in samples of particulate matter (PM) collected on filer papers determined by Ion Chromatography (IC) is proposed. Criteria for differentiating the ion concentration in the filter blank material (FBM)and in the PM sample are taken into account, due to in the analysis of water soluble ions by IC, the ions are desorved from the sample in ultra-pure water, and the levels apported by the constituent material of the blank filter paper could be relevant in most of the cases where the ion concentrations in PM and in the FBM can be comparable. During the development of the procedure is demonstrated the important role that mass determination plays in order to get a precise estimation of the ion concentration. Mathematical relations between estimating error in function of considering negligible the difference between the mass of the filter blank paper and the mass of the collected material are gotten.