A critical review of single particle inductively coupled plasma mass spectrometry - A step towards an ideal method for nanomaterial characterization

Single particle inductively coupled plasma mass spectrometry (spICP-MS or SP-ICP-MS depending on the author) is becoming an important tool for the characterization of nanoparticles (NPs). The method allows determining the size, size distribution, and particle number concentrations of NPs in suspensions after a mere few minutes of measurement. This review is modeled after the concept of an ideal method for atomic spectroscopy introduced by Gary M. Hieftje in his publication dedicated to Howard Malmstadt. This review discusses the instrumental developments in spICP-MS of recent years step-by-step, from the sample introduction system to the detector. The authors identify necessary improvements and suggest directions for further developments which have the potential to bring the method closer to an ideal method for atomic spectroscopy. The review also discusses the literature on coupling spICP-MS to separation and fractionation techniques including capillary electrophoresis (CE), field flow fractionation (FFF), and differential mobility analysis (DMA). The second part of the review is dedicated to the applications of spICP-MS. Key steps in sample preparation and selected instrumental conditions that were used in the published literature are summarized in a tabular form. Most frequently, spICP-MS is used for silver (Ag), gold (Au), and titanium dioxide (TiO2) nanomaterial analysis. Data acquisition was typically performed with millisecond dwell times in the past while a time resolution of hundreds of microseconds has been used more often in the last five years. The table may serve as a guide to choose an experimental procedure depending on the matrix that is present in the sample under investigation.