Single particle inductively coupled plasma mass spectrometry metrology: Revisiting the transport efficiency paradigm

Abstract

Transport efficiency has become a critical parameter in single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) since it is involved in the calibrations to determine different measurands (element mass per particle, particle size and particle number concentration). Specific methods for its determination based on the use of particle standards have been developed and widely applied (particle frequency and particle size methods). A refined indirect method not relying on particle standards is also available (dynamic mass flow method). A number of discrepancies on the accuracy of these methods and their adequacy have become evident, making a revision of the topic pertinent. In fact, the application of the particle frequency and particle size methods determine the transport efficiencies corresponding to the particles or the dissolved element respectively, whereas the solvent transport efficiency is actually measured by the dynamic mass flow method. The use of each of these methods requires assuming different conditions that must be considered. These conditions, together with the sources of bias associated to each method are critically discussed to provide a holistic and harmonized view of transport efficiency in the context of SP-ICP-MS metrology.