Electrospray-dynamic mobility analysis for characterization of engineered nanomaterials in aqueous samples

Understanding the behavior and fate of engineered nanomaterials (ENMs) released to the environment requires measurement of their physicochemical properties in relevant media. Specialized instrumentation is required to be able to detect their changes in physicochemical characteristics (such as agglomeration and dissolution) as ENMs move from the manufactured state to the exposure pathway and ultimately interact with biological systems. This study combined electrospray with dynamic mobility analysis (ES-DMA) for characterizing ENMs in dispersions. The capability of this approach to measure different size ranges of silica, gold, silver and cerium dioxide nanoparticles in dispersions was evaluated. The proposed approach was found to be capable of accurately characterizing nanoparticle size and size distributions in monomodal, polymodal and polydispersed samples. The capability of ES-DMA to resolve polymodal nanoparticle size distributions over a wide size range (from 6 to 217 nm) in a single run facilitates the detection of aggregation/agglomeration processes. Results obtained using ES-DMA were compared with those using single particle inductively-coupled plasma mass spectrometry (SP-ICP-MS). Measurements of particle size and size distribution obtained using ES-DMA compared well with reference values and with results obtained using SP-ICP-MS, showing that this technique is capable of reliable characterization of dispersed ENMs.