(369e) High Throughput Collection and Detection of Environmental Nanoparticles

The increasing prevalence of manufactured nanoparticles in the environment poses new risks to human health, pointing to the need for advanced nanoparticle sampling and analysis approaches capable of continuously monitoring room-sized volumes so that dynamic changes in exposure levels can be rapidly detected. Here we describe our efforts to address this need through development of a new technique that enables nanoparticles to be collected and concentrated at very high flow rates, so that they can be directly detected using a continuous-flow microfluidic approach coupled with particle sizing analysis. Nanoparticle detection is accomplished by harnessing interfacial fluorescence phenomena that uniquely emerge in a microfluidic environment. Fundamental parameters including sensitivity and specificity are characterized to establish detection limits for comparison with current-generation instrumentation. We then explore feasibility of coupling this component with an autonomous Wetted Wall Cyclone (WWC) collector developed in our laboratory and fabricated at Northrop Grumman Inc. This system is capable of performing continuous air sampling at 400 L/min with a cutpoint of 500 nm.  Performance was characterized by sampling colloidal (anatase, 5-30 nm) and amorphous powder (5-30 nm) TiO₂ nanoparticles aerosolized and collected in a laboratory flowcell, and comparing the results against a standard glass fiber filter sampler. Environmental monitoring capability was assessed by sampling air in a freshly painted classroom for 24 hours at 100 L/min. Each hydrosol sample was weighed and quantitated alongside suspensions extracted from the reference filter using inductively coupled plasma mass spectrometry. This analysis indicated that the WWC system achieved collection efficiencies of 83.5% and 56.5% for aerosolized colloidal and amorphous power TiO₂ nanoparticles, respectively. The level of TiO₂ in the painted room air was around 0.2 ppt, however, SiO₂ was also detected at 1 ppb. Spectral analysis of the interfacial fluorescence offers potential to enable chemical fingerprinting to be rapidly performed in order to obtain a detailed picture of nanoparticle exposure levels while simultaneously providing the ability to respond to sudden environmental changes