Book of abstracts of the13th International Conference on Electroanalysis ESEAC, 2010; PIN50:357: Chitosan is a natural widely available biopolymer and increasingly used for most diverse applications. Different chitosans of various molecular weight and deacetylation degrees have been previously checked as for their complexing activity towards selected target heavy metals, such as Zn, Pb, Cd, Cu, Mo and Cr [1,2]. Some rheological properties of cementitious matrices have been seen to improve upon incorporation of those biopolymers, such as water retention, setting time and consistency (through the flow table test). In this paper we report the different complexing patterns found for Zn and Pb when a chitosan derivative is used. These results will be discussed by comparison with the behaviour of the aforementioned non-modified chitosans.