Detection of nanoparticles by single-particle ICP-MS with complete transport efficiency through direct nebulization at few-microlitres-per-minute uptake rates

Measurement of nanoparticle (NP) concentration and size by single-particle inductively coupled plasma mass spectrometry (spICP-MS) usually requires the use of a NP reference material to determine the loss of NPs and/or ions during their transport from the sample solution to the detection system. The determination of this loss, qualified as nebulization efficiency (eta(Nebulization)) and/or transport efficiency (eta(Transport)), is time-consuming, costly and lacks reliability. Nebulization of the NPs directly into the plasma (without a spray chamber) results in eta(Nebulization) = 100% and is thus a promising strategy to avoid these calibration steps. In this work, we used the mu-dDIHEN introduction system: a demountable direct injection high-efficiency nebulizer (dDIHEN) hyphenated to a flow-injection valve and a gas displacement pump. For the first time with a continuous flow nebulizer, complete transport efficiency was reached (i.e. eta(Transport) = 100%). Operated at a very low uptake rate (as low as 8 mu L min(-1)), the mu-dDIHEN accurately and reproducibly determined average diameters of Au-, Ag- and Pt-NPs, in full agreement with their reference values. It was also successfully tested for Au-NPs in complex matrices, such as surface waters. spICP-MS analyses with the mu-dDIHEN sample introduction system only require a dissolved standard calibration to determine NP average diameter (d(NPs) in nm) and number concentration (N-NPs) from the simplified set of equations: (d(NPs)) over bar 3 root 6.I-((NPs) over bar)-Ibckgd). t(d).q(liq) and N-((ps) over bar) = (D-NPs) over bar /q(liq). D. t(d).