Analysis of silver and gold nanoparticles in environmental water using single particle-inductively coupled plasma-mass spectrometry.

The production and use of engineering nanomaterials (ENMs) leads to the release of manufactured or engineered nanoparticles into environment. The quantification and characterization of ENMs are crucial for the assessment of their environmental fate, transport behavior and health risks to humans. To analyze the size distribution and particle number concentration of AgNPs and AuNPs in environmental water and track their stability at low number concentration, a systematic study on SP-ICPMS was presented. The Poisson statistics was used to discuss the effect of dwell time and particle number concentration theoretically on the detection of NPs in solution by SP-ICPMS. The dynamic range of SP-ICPMS is approximately two orders of magnitude. The size detection limits for silver and gold nanoparticle in ultrapure water are 20 and 19nm respectively. The detection limit of nanoparticle number concentration is 8×10(4)particlesL(-1). Size distribution of commercial silver and gold nanoparticle dispersions is determined by SP-ICP-MS, which was in accordance with the TEM results. High particle concentration recoveries of spiked AgNPs and AuNPs are obtained (80-108% and 85-107% for AgNPs and AuNPs respectively in ultrapure and filtered natural water). It indicates that SP-ICPMS can be used to detect AgNPs and AuNPs. The filtration study with different membranes showed that filtration might be a problematic pre-treatment method for the detection of AgNPs and AuNPs in environmental water. Furthermore, the stability of citrate-coated AgNPs and tannic acid-coated AuNPs spiked into filtrated natural and waste water matrix was also studied at low concentration using SP-ICP-MS measurements. Dissolution of AgNPs was observed while AuNPs was stable during a ten day incubation period. Finally SP-ICPMS was used to analyze NPs in natural water and waste water. The results indicate that SP-ICPMS can be used to size metallic nanoparticles sensitively of low concentration under realistic environmental conditions.