Non-spectral interferences in single-particle ICP-MS analysis: An underestimated phenomenon

This work demonstrates the effect of NaCl and carbon-related interferences on the analysis of arsenic and silver nanoparticles (NPs) by single-particle inductively coupled plasma mass spectrometry. Spectral interference caused by ArCl⁺ ions disturbing arsenic NPs analysis was eliminated using ammonia as reaction gas in a dynamic reaction cell of inductively coupled plasma mass spectrometer. In comparison to aqueous dispersions, non-spectral interferences caused by sodium lead to under-evaluation of arsenic and silver NPs diameter by about 7% and 15% at NaCl concentration of 450 mg L^-1 and about 28% and 41% at NaCl concentration of 4500 mg L^-1, respectively. As a consequence of lower transport efficiency, sodium non-spectral interferences also lead to about a 9% lower number of detected NPs for dispersions of both arsenic and silver NPs in 4500 mg L^-1 NaCl. On the contrary, measurement of NPs in matrices containing methanol gives results where Ag and As NPs diameter is over-evaluated by about 3% and 15% at a methanol content of 1% (v/v) and about 6% and 20% at a methanol content of 2% (v/v), respectively, in comparison to aqueous dispersions. In addition, the organic carbon species behave as surfactants and increase the transport efficiency; this leads to an increase in the determined number concentration of NPs. In comparison to aqueous dispersions, this is over-evaluated by about 17% for Ag NPs and about 10% for As NPs at a methanol content of 5% (v/v).