Improvements in the detection and characterization of engineered nanoparticles using spICP-MS with microsecond dwell times

Abstract

The imminent release of engineered nanomaterials (ENPs) into the environment has raised several questions regarding their fate, transport, and toxicity. However, their small size, expected low concentrations (ng L⁻¹), and the high environmental background of naturally occurring nanomaterials make detection and characterization difficult. In recent years, single particle ICP-MS (spICP-MS) has been developed as a promising technique to detect and characterize engineered nanoparticles in biological and environmental matrices. Improvements in the spICP-MS technique were made in this study by employing 100 microsecond dwell times. Commercially available hardware and software were developed to fully capture multiple data points over the fast transient (~500 μs) nanoparticle events, which provides accurate particle sizing and counting. Reducing the background signal facilitated the characterization of Ag NPs even in the presence of ten-fold higher Ag⁺ concentration. By improving the time resolution between particle events, the upper limit of the dynamic range of Au NP concentration was increased to several μg L⁻¹. These short dwell times also provide detection of two elements in the same nanoparticle, opening the door for possible environmental applications with the prospect of obtaining particle-by-particle elemental compositions. These improvements help further establish spICP-MS as a leading analytical technique for the detection and characterization of metal-containing ENPs, and introduces new possibilities for differentiating engineered nanomaterials from their naturally occurring analogues.