Simple Extraction and Ultrasensitive Determination of Nanoscale Silver from Environmental Waters

Silver speciation is an important step for any program aiming to provide precise insights into the chemical transformation and evaluate the biological toxicity. Nonetheless, reliable speciation by easy-to-use and sensitive analytical approaches is still challenging for silver in natural waters at environmentally relevant levels. Herein, this study established a simple, fast, and robust analysis approach combining protein corona-mediated extraction with inductively coupled plasma mass spectrometry analysis to selectively separate nanoscale silver (n-Ag) from waters and sensitively quantify its mass concentration. Bovine serum albumin (BSA) was selected as the extractant to form protein corona on the n-Ag surface, followed by the selective extraction of n-Ag with addition of Na2S2O3. After the optimization of the extraction solvent concentration (i.e., 50 mg/L BSA), pH (i.e., 4.0), extraction time (i.e., 5 min), inorganic salt concentration (i.e., 1% m/v NaNO3), and incubation temperature and time (i.e., 80 degrees C and 45 min), acceptable recoveries of the spiked n-Ag (67.3-83.1%) were achieved in three environmental samples with a detection limit of 0.95 ng/L. The interference from natural humic acid, salinity, and other particles could be efficiently negligible. Transmission electron microscopy analysis showed that no size and/or shape changes were observed after extraction, making this approach attractive in practical application. Compared with the conventional cloud point extraction method, this new method exhibited superior selectivity to n-Ag at environmentally relevant levels in waters. Consequently, our work offers a promising way to highly enrich and sensitively quantify n-Ag in complex water matrices, which will allow the improvements to track the nanoparticles in the environment, promote the research on the environmental behaviors of n-Ag, and better evaluate its risk to the environment and human health.