Evaluation of a cloud point extraction method for the preconcentration and quantification of silver nanoparticles in water samples by ETAAS

A simple and reliable analytical method using instrumentation available in most of the laboratories has been developed for the separation and determination of silver nanoparticles in water samples. Cloud point extraction (CPE) was used for the separation of silver nanoparticles (AgNPs) from the sample and these nanoparticles were then determined by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to the cloud point extraction procedure (Triton X-114 concentration, type of complexing agent (EDTA or Na2S2O3), pH, incubation temperature, incubation and centrifugation time) were selected using a multivariate approach (designs of experiments); 8.6% (v/v) Triton X-114, 750 mu L saturated EDTA and pH 7 were selected as the optimum conditions. Calibration standards in a concentration range from 0 to 10 mu g L-1 of AgNPs were subjected to the CPE procedure to obtain quantitative recoveries. The LOD and LOQ were 0.04 and 0.13 mu g L-1, respectively. The method is selective for the extraction of AgNPs, and ionic Ag remains in the aqueous phase. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was used to evaluate the effect of the CPE procedure in particle size, and no changes were observed. Finally, the procedure was applied to wastewater samples spiked with nanoparticles with quantitative recoveries.