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

Single particle inductively coupled plasma mass spectrometry is an emergent ICPMS method for detecting, characterizing, and quantifying nanoparticles. Although the number of applications reported to date is limited, the relatively simple instrumental requirements, the low number concentration detection levels attainable, and the possibility to detect both the presence of dissolved and particulate forms of an element make this methodology very promising in the nanoscience related areas.

The metrological criteria for the implementation of the single particle inductively coupled plasma mass spectrometry (SP-ICPMS) methodology applied to nanoparticle size characterization and quantification have been investigated. The SP-ICPMS basis involves a process of counting events corresponding to individual nanoparticles, which requires (i) isolation of the contribution of the nanoparticles from that of the background/dissolved analyte, and (ii) avoiding the occurrence of multiple-nanoparticle events. A criterion based on three times the standard deviation of the continuous background (3s) was selected as the threshold for discrimination of nanoparticle events from the background. Because the detectability of nanoparticles depends on both the size and number concentration, this 3s criterion was also selected for detection of nanoparticles at the size detection limit and concentrations over the number concentration detection limit. However, at very low number concentrations, a less restrictive criterion must be used. The selection of a critical nanoparticle number concentration, based on the sample introduction and data acquisition parameters, allows the minimization of the occurrence of multiple-nanoparticle events, as well as controlling of the precision associated with the counting of nanoparticle events. Under such conditions, the standard uncertainty associated with the determination of number concentrations was 5%. The uncertainty for the determination of nanoparticle diameters was also studied, varying from 3 to 10% for diameters in the range of 100–40 nm, respectively. Reliable average number concentrations and sizes were obtained, although the number size distributions showed a significant broadening contribution due to the SP-ICPMS measurement process. The feasibility of SP-ICPMS for the implementation of the European Commission definition of "nanomaterial" was studied by analyzing commercial silver nanoparticle suspensions

A set of three types of silver nanoparticles (Ag NPs) are prepared, which have the same Ag cores, but different surface chemistry. Ag cores are stabilized with mercaptoundecanoic acid (MUA) or with a polymer shell [poly(isobutylene-alt-maleic anhydride) (PMA)]. In order to reduce cellular uptake, the polymer-coated Ag NPs are additionally modifi ed with polyethylene glycol (PEG). Corrosion (oxidation) of the NPs is quantifi ed and their colloidal stability is investigated. MUA-coated NPs have a much lower colloidal stability than PMA-coated NPs and are largely agglomerated. All Ag NPs corrode faster in an acidic environment and thus more Ag(I) ions are released inside endosomal/lysosomal compartments. PMA coating does not reduce leaching of Ag(I) ions compared with MUA coating. PEGylation reduces NP cellular uptake and also the toxicity. PMA-coated NPs have reduced toxicity compared with MUA-coated NPs. All studied Ag NPs were less toxic than free Ag(I) ions. All in all, the cytotoxicity of Ag NPs is correlated on their uptake by cells and agglomeration behavior

A method for determining the size of silver nanoparticles and their quantification by asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (ICP-MS) is proposed and was tested in consumer products. Experimental conditions were studied in detail to avoid aggregation processes or alteration of the original size distributions. Additionally, losses from sorption processes onto the channel membrane were minimized for correct quantification of the nanoparticles. Mobile phase composition, injection/focusing, and fractionation conditions were evaluated in terms of their influence on both separation resolution and recovery. The ionic strength, pH, and the presence of ionic and nonionic surfactants had a strong influence on both separation and recovery of the nanoparticles. In general, better results were obtained under those conditions that favored charge repulsions with the membrane. Recovery values of 83 ± 8% and 93 ± 4% with respect to the content of silver nanoparticles were achieved for the consumer products studied. Silver nanoparticle standards were used for size calibration of the channel. The results were compared with those obtained by photon correlation spectroscopy and images taken by transmission electron microscopy. The quantification of silver nanoparticles was performed by direct injection of ionic silver standard solutions into the ICP-MS system, integration of the corresponding peaks, and interpolation of the fractogram area. A limit of detection of 5.6 μg L(-1) silver, which corresponds to a number concentration of 1×10(12) L(-1) for nanoparticles of 10 nm, was achieved for an injection volume of 20 μL.

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The occurrence of SeNPs in commercial Se-rich yeasts was confirmed by SP-ICPMS for the first time.

A method for the detection and quantification of nanoplastics (NPTs) at environmentally relevant concentrations was developed. It is based on conjugating nanoplastics with functionalized metal (Au)-containing nanoparticles (NPs), thus making them detectable by highly sensitive inductively coupled plasma mass spectrometry (ICP-MS) operated in single particle (SP) mode. The selectivity of the method was achieved by the coupling of negatively charged carboxylate groups present at the surface of nanoplastics with a positively charged gelatin attached to the custom-synthesized AuNPs. The adsorbed Au produced a SP-ICP-MS signal allowing the counting of individual nanoplastic particles, and hence their accurate quantification (< 5% error). Polystyrene (PS) particle models with controlled surface functionalization mimicking the nanoplastics formed during natural degradation of plastic debris were used for the method development. The nanoplastic number concentration quantification limit was calculated at 8.4 x 10 5 NPTs L-1 and the calibration graph was linear up to 3.5 x 10 8 NPTs L-1. The method was applied to the analysis of nanoplastics of up to 1 µm in drinking, tap and river water. The minimum detectable and quantifiable size depended on the degree of functionalization and the surface available for labeling. For a fully functionalized nanoplastic, the lower size detectable by this strategy is reported as 135 nm. In this study, authors use the recommendation for the definition of nanoplastics as plastic particles with sizes ranging between 1 nm and 1 µm, although it has not been accepted by a dedicated organization.