Selective identification, characterization and determination of dissolved silver(i) and silver nanoparticles based on single particle detection by inductively coupled plasma mass spectrometry

Abstract

The different behaviours of dissolved silver and silver nanoparticles under ICP-MS single particle detection conditions have been used to differentiate directly between both forms of silver in aqueous samples. Suspensions containing silver nanoparticles at number concentrations below 10^9 L-1 and/or dissolved Ag(I) are introduced into the ICP-MS by conventional pneumatic nebulization and measured with a time resolution of 5 ms. Each silver nanoparticle is converted in the ICP into a packet of ions, which are detected as a single pulse, whose intensity is proportional to the number of silver atoms in the nanoparticle, whereas dissolved silver produces pulses of averaged constant intensity. The frequency plots with respect to the intensity measured for each pulse show independent distributions for dissolved silver and silver nanoparticles, whose profiles are also different (Poisson and lognormal, respectively). Size limits of detection for pure Ag nanoparticles of 18 nm, equivalent to a silver mass of 32 ag, were obtained. Number concentration limits of detection of 1 X 10^4 L-1 can be achieved. A methodological approach for identification, characterization and determination of mass and number concentration of dissolved Ag(I) and silver nanoparticles at environmentally relevant concentrations is presented

Rapid Chromatographic Separation of Dissoluble Ag(I) and Silver-Containing Nanoparticles of 1–100 Nanometer in Antibacterial Products and Environmental Waters

“…While single particle ICP-MS was proposed for quantification of AgNPs and dissolved Ag(I), it only allows for the quantification of NPs with sizes ≥20 nm, as small NPs are hardly distinguished from the metal ions. 28,29 Although filtration, 30 centrifugation, 7 centrifugal ultrafiltration, 11 and diffusion gradient thin film (DGT) 31 were off-line coupled with ICP-MS, inductively coupled plasma optical emission spectrometer (ICP-OES) or atomic absorption spectroscopy (AAS) for the analysis of AgNPs and Ag(I), these separation techniques are unable to distinguish the small sized AgNP clusters from Ag(I). While this limitation can be overcome by separation with dialysis, 18 cloud point extraction (CPE), 32−37 and ion-exchange resin method, 35,38 these techniques required a relatively long separation time that is between 40 min and 45 h. To overcome this restriction, ICP-MS was online coupled with asymmertric flow field-flow fractionation 39−41 for selective determination of AgNPs in the presence of Ag(I), and with liquid chromatography (LC) 42 or capillary electrophoresis (CE) 43 for speciation test of AgNPs and Ag(I).…”

Current status and future direction for examining engineered nanoparticles in natural systems

“…[92][93][94][95][96] However, the size detection limit for this technique is dependent on the signal generated by the ablation of the nanoparticle, which may require a significant amount of ions to generate a recognisable intensity pulse. In addition, although its elemental specificity is a desirable attribute, it may be unable to differentiate between an engineered and naturally occurring nanomaterial of the same elemental composition.…”

Determination of emerging contaminants in environmental matrices

“…In practice, the minimum complete PSD that can be detected depends also on the polydispersity (width) of the sample. In the current case, it was possible to detect the complete PSD of Ag-NPs standards with 30 nm nominal size, in accordance with previous studies (Mitrano et al, 2012a;Laborda et al, 2011).…”