Détection et caractérisation de nanoparticules d’oxyde de zinc par spectrométrie de masse à plasma inductif en mode particule unique (single-particle ICPMS)
The increased production, use and release of engineered nanomaterials (NM) is concerning considering their possible persistence in the environment and their potential toxic issues. Unfortunately, actual knowledge about their presence in natural media is limited, mainly because of their very low concentrations (ng L-1) and the complex matrices in which they are suspected to be found. Therefore, there is a great need to develop analytical techniques that are sensitive, selective and adapted to those natural matrices. To do so, single-particle inductively coupled plasma (SP-ICPMS) is a very promising analytical technique. Allowing the one by one detection of metallic particles, SP-ICPMS has already been used for the characterization of NM in complex media. However, size detection limits (SDL) are higher for some metallic NM, which are, like the Zn base NM, rapidly dissolved or that have a natural high concentration of the ionic form in the sample. As a result, the use of SP-ICPMS for the detection and characterization of zinc oxide nanoparticles (ZnO NP), which is one of the most used in the industry, is a big challenge. To overcome it, an ion-exchange technique was used to remove the Zn2+ and its weakly bonded forms present in solution before their analysis. This technique has successfully been adapted to a highly sensitive ICPMS in order to lower the SDL of ZnO NP, going from 32 to 8.2 nm. To test the setup for a natural media, ZnO NP were spiked and analyzed in river water. After 24 h, particles were found to be more stable in the river water, most probably because of its higher pH. Also, the developed method allowed the analysis of natural zinc and copper containing colloids in river and in rainwaters. Stability of these particles in the rainwater was followed during one month during which the metal mass of the particles on average slightly decreased.
Single-particle inductively coupled plasma mass spectrometry Nanoparticles Zinc oxide Natural waters