Explorations into Nanoparticle Analysis by Single Particle Inductively Coupled Plasma Mass Spectrometry

Abstract

The growing use of nanoparticles in a wide variety of industries has facilitated an increasing need to detect, quantify, and size these materials. Quality control and detection of environmental contaminations are pressing areas of concern for nanoparticle analysis. A wide range of techniques promises the ability to achieve these goals; however, many struggle in certain key areas, namely reproducibility, expense, and time required to take measurements. A technique that is growing in popularity for nanoparticle analysis is single particle inductively coupled plasma mass spectrometry (spICPMS) as it solves many of the issues that other techniques struggle with, namely reproducibility and time required for analysis. A new peak area calibration technique is shown for spICPMS and compared to the conventional average intensities approach. The peak area technique does not require measurement of the transport efficiency while still providing statistically similar results, thus eliminating one potential source of error. One area where spICPMS struggles is the sensitivity of the analysis. The sensitivity is limited by the transport efficiency of the spray chamber. To attempt to improve the sensitivity of the spICPMS method, this thesis examines modified sample introduction techniques. Flow injection and mono segmented flow analysis (MSFA) are both techniques where a discrete amount of sample is injected into a carrier stream for analysis. Additionally, infrared (IR) heating of the sample introduction system to create smaller droplets increasing the amount of sample that reaches the plasma is also examined. MSFA give similar size distributions to the conventional approach while improving the transport efficiency leading to improved precision for the measurement of nanoparticles as well as improved sensitivity and limits of detection for solution analysis. IR heating of the sample introduction system also improved the transport efficiency and therefore the sensitivity of the analysis; however, raising the temperature too high resulted in the background signal being increased. The optimal temperature that was found was 60°C. Calibrating spICPMS with the peak areas approach reduces the number of measurements required and lowers the error associated with the analysis, while using an MSFA approach as well as IR heating can increase transport efficiency and improve the sensitivity.