2 research outputs found
Detection and Characterization of ZnO Nanoparticles in Surface and Waste Waters Using Single Particle ICPMS
The increasing production of ZnO
nanoparticles (nZnO) makes their
analysis and characterization extremely important from an ecological
risk perspective, especially at the low concentrations at which they
are expected to be found in natural waters. Single particle ICPMS
(SP-ICPMS) is one of the few techniques available to detect and characterize
nanoparticles at environmentally relevant concentrations. Unfortunately,
at the very low particle concentrations where SP-ICPMS is performed,
significant dissolution of the nZnO generally increases background
levels of dissolved Zn to the point where measurements are not generally
possible. By hyphenating SP-ICPMS with an ion-exchange resin, it was
possible to characterize and quantify nZnO in order to gain insight
into the nature of the nZnO in natural waters. Spiked and unspiked
water samples were analyzed using a SP-ICPMS that was coupled to a
column containing a strong metal binding resin (Chelex 100). In addition
to the detection of ZnO nanoparticles and the determination of a size
distribution in natural waters, it was possible to partition the dissolved
Zn among free and/or labile and strongly bound Zn fractions. In two
natural waters, a high proportion (ca. 93–100%) of dissolved
Zn was measured, and the residual ZnO particles were mainly composed
of small agglomerates (average sizes ranging from 133.6 to 172.4 nm
in the surface water and from 167.6 to 216.4 nm in the wastewater
effluent). Small numbers of small nanoparticles were also detected
in nonspiked waters
Improvements to Single Particle ICPMS by the Online Coupling of Ion Exchange Resins
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