Sols of Silver Nanoparticles as Analytical Reagents for the Determination of Active Chlorine in Water Samples by Spectrophotometry and Photometric Titration

Resumo

Sols of silver nanoparticles surface-stabilized by cetyltrimethylammonium bromide or polyvinylpyrrolidone can be used for the determination of active chlorine in water samples. As analytes modeling active chlorine in water, we used freshly prepared sodium hypochlorite solutions. Because of the high values of standard electrode potentials of reduction half-reactions, active forms of chlorine can oxidize silver nanoparticles, exhibiting the effect of surface plazmon resonance with an absorption maximum near 400 nm. The absorption intensity of silver nanoparticles correlates with the concentration of sodium hypochlorite. This effect was used for the qualitative and quantitative determination of active chlorine in water samples. The quantitative characteristics of the described method were obtained for two versions of analysis, spectrophotometry and photometric titration. The calibration graphs for both versions were similar and linear in the range of sodium hypochlorite concentrations 0.1–2.5 mM.