Single-particle inductively coupled plasma mass spectrometry for the analysis of inorganic engineered nanoparticles: Metrological and quality issues

Abstract This chapter covers the metrological aspects of the SP-ICP-MS technique including the different types of analytical information available and the quality of such information. Basic expressions to relate the different signal domains in SP-ICP-MS with the corresponding information domains, together with the measurands involved, are summarized in the first section, paying special attention to the different calibrations needed. The effects of the limited availability of appropriate reference materials and standards on the traceability of the results is discussed. The validation of the methods requires harmonized performance parameters applied to both particle size (diameter for spherical particles) and mass/number concentrations. The few validated methods available in literature have been reviewed and selectivity, precision, trueness, limits of detection or measurement range are summarized and compared. Evaluation of the uncertainty has shown the relevance of using well-characterized standards for particle diameter determination due to the large uncertainty associated to it. Analysis of the uncertainty associated with the measurement of number concentration by SP-ICP-MS shows that the determination of the transport efficiency is the main contribution factor. Quality control procedures have been applied to some extent in different studies focused on the detection, size characterization and quantification of metal-bearing nanoparticles in complex samples, like consumer products, foods, environmental or biological samples. In many cases, the unknown nature of the nanoparticles, along with their small sizes and instrumental constraints, limit the information achievable, which cannot be considered quantitative and is restricted to the detection of the presence of nanoparticles containing the element measured.