Herein, we introduce
the first relative single-particle
inductively
coupled plasma mass spectrometry (spICP-MS) approach where size calibration
is carried out using the target NP itself measured under different
instrumental conditions without external dependence on the complex
and prone-to-error determination of transport efficiency or mass flux
calibrations, in contrast to most spICP-MS approaches. The simple
approach proposed allows determining gold nanoparticle (AuNP) sizes,
with errors ranging from 0.3 to 3.1% (corroborated by HR-TEM). It
has been demonstrated that the changes observed in the single-particle
histograms obtained for a suspension of AuNPs under different sensitivity
conditions (n= 5) are directly and exclusively related
to the mass (size) of the target AuNP itself. Interestingly, the relative
nature of the approach shows that once the ICP-MS system has been
calibrated with a generic NP standard, it is no longer necessary to
repeat the calibration for the size determination of different unimetallic
NPs carried out along time (at least 8 months), independently of their
size (16–73 nm) and even nature (AuNP or AgNP). Additionally,
neither the NP surface functionalization with biomolecules nor protein
corona formation led to significant changes (relative errors slightly
increased 1.3- to 1.5-fold, up to 7%) in the NP size determination,
in contrast to conventional spICP-MS approaches where relative errors
increased 2- to 8-fold, up to 32%. This feature could be especially
valuable for the analysis of NPs in real samples without the need
of matrix-matched calibration.