Improvements to Single Particle ICPMS by the Online
Coupling of Ion Exchange Resins
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Abstract
Single
particle ICPMS (SP-ICPMS) is becoming a very promising technique for
nanoparticle detection and characterization, especially at very low
concentrations (∼10<sup>–12</sup>–10<sup>–10</sup> M). Nonetheless, the ability of the technique to detect smaller
nanoparticles is presently limited by the setting of threshold values
for the discrimination of nanoparticles from the dissolved metal background.
In this study, a new approach to attaining lower particle size detection
limits has been developed by the online coupling of an ion exchange
column (IEC) with SP-ICPMS (IEC-SP-ICPMS). The IEC effectively removes
the continuous signal of dissolved metal, allowing for both lower
detection limits and an improved resolution of solutions containing
multiple particles. The feasibility and the efficiency of this coupling
were investigated using silver nanoparticles in the presence of various
concentrations of Ag<sup>+</sup> and other major ions (Mg<sup>2+</sup>, Ca<sup>2+</sup>, Na<sup>+</sup>, K<sup>+</sup>, and Cl<sup>–</sup>). The online elimination of the dissolved metal made data processing
simpler and more accurate. Following the addition of 1 to 4 μg
L<sup>–1</sup> of Ag<sup>+</sup> spikes, symmetric particle
size distributions were obtained using IEC-SP-ICPMS, whereas the use
of SP-ICPMS alone led to asymmetric distributions, especially for
nanoparticle sizes below 60 nm. Although this proof of principle study
focused on nanosilver, the technique should be particularly useful
for any of the metal based nanoparticles with high solubilities