Development of reusable magnetic chitosan microspheres adsorbent for selective extraction of trace level silver nanoparticles in environmental waters prior to ICP-MS analysis

Abstract

Solid-phase extraction (SPE) based on reusable magnetic chitosan microspheres was coupled with ICP-MS for separation and quantification of silver nanoparticles (AgNPs) in the presence of silver ions in environmental water samples. The monodisperse magnetic chitosan microspheres with an average size of 2µm were engineered using suspension cross-linking technique, and characterized and investigated for its application as SPE adsorbent. Parameters affecting the SPE were optimized, and the best performance was achieved by extracting a 20mL sample (pH 4.5) with 10mg adsorbent for 90min, followed by elution with 1mL 1% (w/v) thiourea in 10% (v/v) nitric acid for 10min. The detection limit, calculated as 3s (s, standard deviation for 11 blank readings), for three AgNPs coated with polyvinyl pyrrolidone (PVP), citrate and polyvinyl alcohol (PVA) and sizes of 31, 40, 46nm, respectively, were in the range of 0.016‒0.023μg/L. The repeatability and reproducibility (RSD, n=7) at a spiking level of 0.1μg/L AgNPs were 4.2% and 8.1%, respectively. The developed method has been applied in the analysis of AgNPs in river, lake and wastewater samples, with excellent extraction efficiencies (84.9‒98.8%) for AgNPs at spiking levels of 0.86 and 8.70μg/L. The cationic chitosan microspheres showed good species selectivity and reusability for extraction of AgNPs in the presence of Ag+, and hence the proposed method is simple, cost effective and environmentally friendly.