AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Single Particle Characterization of Nanoparticle Metal-Oxides by ICP-MS
BRIAN MAJESTIC, Manuel Montano, James Ranville, University of Denver
Abstract Number: 566 Working Group: Engineered Nanoparticles: Emissions, Transformation and Exposure
Abstract Metal oxide nanoparticles (NP) (e.g. Fe$_2O$_3, Al$_2O$_3, SiO$_2) are used in a variety of products ranging from groundwater remediation, photoactive cosmetics and polishing slurries in microchip fabrication, but can also be effective vectors for contaminant transport in the environment and may be responsible for inhalation health effects. Single-particle (sp) inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool capable of detecting, counting and sizing nanoparticles in complex matrices. Individual nanoparticles in their pure elemental state (e.g., Ag and Au) have been successfully sized by ICPMS at sizes down to ~ 20 nm. Metal oxides are more difficult to detect using ICPMS because 1) they often suffer from significant molecular interferences, as is the case for $^(56)Fe ($^(40)Ar$^(16)O) and $^(28)Si ($^(14)N$_2) and 2) there is less analyte mass per particle due to the presence of oxygen. In these cases, a collision cell pressurized with helium gas can be used to reduce/remove the interferences allowing for sizing of the analyte. In the current study, collision cell sp-ICP-MS has been used to study silica (SiO$_2) nanoparticles and alpha-hematite (Fe$_2O$_3) colloids to develop a method for detecting these particles in environmental samples. alpha-Hematite particles as small as 60 nm and silica particles as small as 200 nm have been detected by sp-ICP-MS. However, the sizing of the particles has proven to be troublesome and requires further method development. Research is ongoing to not only characterize these particles, but to also study adsorbed contaminants onto nanoparticles (e.g., copper adsorbed onto hematite or metals adsorbed onto black carbon). When paired with a water-trap type of sampler, such as a particle-into-liquid sampler (PILS), this technique has the capability to potentially size and detect, in semi-real time, individual airborne nanoparticles.