Organics non-spectral interferences on nanoparticle characterization by means single particle inductively coupled plasma mass spectrometry

Abstract

The number of works devoted to nanomaterials characterization in organic matrices by means spICP-MS grows every year, but limited information is available about the non-spectral interferences generated by this type of matrices. A better understanding of this interference is a prerequisite for developing more robust methodologies and improving spICP-MS metrology. The goal of this work is to investigate non-spectral interferences due to organics on nanoparticles (NPs) characterization (i.e., number concentration and size distribution) by means spICP-MS. To this end, the influence of NPs composition and size (i.e., Au-, Pt- and SeNPs), carbon source (i.e., 6% w w-1 glycerol and 10% w w-1 ethanol), ICP-MS operating conditions (i.e., sampling depth and nebulizer gas flow) and instrument design on matrix effects have been evaluated. It was observed that 10% w w-1 ethanol give rise to positive matrix effects on the number concentration due to changes on aerosol generation and transport with regard water standards. Irrespective of the organic source employed, either positive or negative bias on the size distributions can be obtained and these effects depend on plasma operating conditions, instrument characteristics and NPs composition. In addition to changes on transport efficiency, matrix effects on size distribution also depend on plasma characteristics and carbon-based charge transfer reactions (Au and Se). Organic non-spectral interferences can be mitigated by means internal standardization. When operating with 10% w w-1 ethanol, two internal standards (ionic solution plus a NPs suspension of known concentration) are simultaneously required for correcting changes on analyte ionization and transport. For 6% w w-1 glycerol, however, just a single internal standard (ionic solution) is necessary since this matrix does not affect aerosol generation and analyte transport. A novel measurement procedure is proposed for measuring the internal standards and the NPs of interest without compromising sample throughput.