Single particle inductively coupled plasma mass spectrometry (spICP-MS)

Abstract Single particle ICP-MS (spICP-MS) is gaining increasing popularity for the determination of nanoparticle number-based concentration due to its high sensitivity, elemental specificity, and the development of much improved hardware with fast detectors and software able to handle large amount of data produced during spICP-MS experiments, even when using microsecond detection. In spICP-MS, a very dilute suspension is introduced into the instrument, such that only one particle at a time enters the plasma. The ICP atomizes and ionizes the constituents of the particle, which are then detected using the mass spectrometer. Apart from number concentration, other particle characteristics such as mass concentration and the mass of individual particles can be determined using spICP-MS. The latter can be converted to particle diameter for objects of known geometries, also providing information about the number-based size distribution of particles in the sample. SpICP-MS, unlike other particle counting techniques, is also capable of measuring the dissolved fraction of the element within the same run. This chapter will address the principles, advantages, and remaining challenges of spICP-MS for number concentration and size determination of inorganic nanoparticles (NPs). It will also discuss the main parameters that contribute to the accuracy and uncertainty of the number concentration data with particular emphasis on the determination of the NP transport efficiency and the existing approaches for its determination.