Self-standing chitosan film loaded with silver nanoparticles as a tool for selective determination of Cr(VI) by ICP-MS

• Ecofriendly method for synthesis of silver nanoparticles and their incorporation in chitosan nanocomposite.
• Selective sorption of Cr(III) on self-standing chitosan film loaded with silver nanoparticles.
• Simple method for determination of Cr(VI) in surface waters usable in the routine analytical practice.

A fast, simple and sensitive method was developed for separation and speciation of Cr species using dispersive solid phase extraction prior determination by ICP-MS. The selective determination of toxic Cr(VI) in surface waters is achieved after separation of Cr(III) by sorption on self-standing chitosan film loaded with silver nanoparticles (CHS-AgNPs). Completely green synthetic procedure was used for the preparation of AgNPs, which includes d-(+) raffinose as a non-toxic, environmentally benign reducing and capping agent and NaOH as a base reaction catalyst. The raffinose-coated Ag NPs were blended with chitosan to form polyelectrolyte complex that was cast into stable self-standing film. The parameters affecting the extraction efficiency (pH, sorption time, sample volume) of nanocomposite film toward Cr(III) and Cr(VI) were carefully optimized. Effective separation of Cr species between solid and liquid phase is demonstrated by simply tuning the pH value of the sample solution. The analytical method developed is validated under optimized conditions - the detection limit of 0.02 μg L− 1 and determination limit of 0.06 μg L− 1 were achieved for both Cr species; the relative standard deviation varied from 3 to 5% for Cr concentrations in the sample solution over the range 0.05–5 μg L− 1. The accuracy is established by analyzing certified reference materials.