Detection and characterization of silver nanoparticles in aqueous matrices using asymmetric-flow field flow fractionation with inductively coupled plasma mass spectrometry.

Engineered nanomaterials (EN) may be released into the environment as a result of their use in various consumer products. Silver nanoparticles (nAg) are widely used as an antimicrobial agent in personal care and household products, and in textiles. Since there is high potential for nAg to be released into municipal wastewater and then discharged into the aquatic environment, there is a need to develop methods for the analysis of these materials in aqueous matrices. Asymmetric-flow field flow fractionation (AF4) with on-line detection by ultra violet-visible (UV-Vis) spectroscopy or inductively coupled plasma mass spectrometry (ICP-MS) was used to detect and characterize nAg in aqueous matrices. Analysis of a mixture of 20, 40 and 60 nm nAg standards suspended in water resulted in a well resolved fractogram. Retention times of nAg separated by AF4 were correlated with the particle sizes of the standards. The limit of detection (LOD) for analysis of nAg using the on-line AF4/ICP-MS method was 0.80 ng mL(-1). Two calibration approaches (i.e., external calibration and standard addition) were used to quantify nAg concentrations, and both methods gave similar results. Using the on-line AF4/ICP-MS analytical method, nano-sized Ag was detected and quantified in untreated wastewater (i.e., influent) collected from a wastewater treatment plant. The concentration and the modal size of nAg in the influent were 1.90 ng mL(-1) and 9.3 nm respectively.