Ligand-assisted magnetic solid phase extraction for fast speciation of silver nanoparticles and silver ions in environmental water

In this work, poly(1-vinylimidazole) functionalized magnetic nanoparticles (PVIM-MNPs) were prepared and adopted for the adsorption of silver nanoparticles (AgNPs) and silver ions (Ag ions). With the use of mercaptosuccinic acid as a ligand exchanger, both of AgNPs and Ag ions could be adsorbed on the PVIM-MNPs and the sequential desorption of Ag ions and AgNPs was easily achieved by using Na2S2O3 and HNO3, respectively. Based on it, a new approach by coupling ligand-assisted magnetic solid phase extraction (MSPE) with graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the speciation of AgNPs and Ag ions in environmental water samples. Factors affecting MSPE of AgNPs and Ag ions were investigated and the optimized conditions were established. With an enrichment factor of 100-fold, the detection limits of the proposed method were 7.5 and 8.2 ng L-1 for Ag ions and AgNPs with relative standard deviations of 6.4% and 7.0% (c = 50 ng L-1, n = 7), respectively. The proposed ligand-assisted MSPE-GFAAS method has the advantages of high sensitivity, low cost and easy operation, and could be used for the quantification of Ag ions and various coating modified AgNPs with a size range of 5-120 nm in environmental waters.