Development of a cloud point extraction method combined with ETAAS and ICP-MS for the preconcentration and quantification of silver as nanoparticles in saline samples.

The increasing industrial use of silver nanoparticles (AgNPs) has led to interest in their determination in different types of environmental complex samples, including saline matrices such as aquaculture waters. A simple, reliable, and green analytical method using instrumentation available in most of the laboratories has been developed for the determination of silver as nanoparticles in saline samples. Cloud point extraction (CPE) was used for the separation of AgNPs from seawater, and silver was then determined in the surfactant-rich extracts by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to ETAAS and the cloud point extraction procedure (Triton X-114 concentration, volume of complexing agent (EDTA), pH and type of buffer, effect of repetitive extraction, matrix modifier, etc) were evaluated. A concentration of Triton X-114 of 12% (v/v), a volume of 750 μL of saturated EDTA, and a pH of 7.0 were selected as the optimum conditions for the separation of AgNPs. Standard addition calibration solutions in a concentration range from 0 to 3.0 μg L^-1 of AgNPs were subjected to the CPE procedure and used for silver determination by ETAAS. The LOD and LOQ were 0.038 and 0.125 μg L^-1 of silver (as AgNPs), respectively. The method is precise (whole procedure 9.7%) and accurate (recovery percentages 99±4%), showing a good selectivity for the extraction of AgNPs, while ionic Ag remains in the aqueous phase. Moreover, the results of size analysis of the nanoparticles in the surfactant extracts of seawater samples spiked with AgNPs (40 and 60 nm) by SP-ICP-MS and TEM were in good agreement.