Eluent composition effect.

<p>Retention factors of polystyrene standards measured using HDC in three different eluents (column type 2, three replicates).</p

Typical ICP-MS parameters used in this study.

<p>Typical ICP-MS parameters used in this study.</p

Flow rate effect.

<p>a: Retention factors of gold nanoparticle standards measured using HDC at different flow rates (column type 1; 3 replicates for 1.7 mL min⁻¹ and 2 replicates for the other flow rates and); b: Retention factors of polystyrene standards (nominal diameters: 100 nm, 300 nm and 1000 nm) measured at different flow rates (column type 2, two replicates per suspension and flow rate value). The lines are provided for ease only.</p

Agglomerates measurements.

<p>HDC time-resolved measurements of a latex suspension induced to agglomerate by adding CaCl₂. Time was measured as of the addition of salt. The time zero point corresponds to the initial suspension before adding salts. The wavelength for the UV detector was 256 nm.</p

Effective diameters of silver nanoparticles in synthetic surface water.

<p>Estimated effective diameter using HDC-ICP-MS of citrate-stabilised silver nanoparticles (nominal diameter 40 nm) in different media: MQW and MSW containing X mg L⁻¹ of humic acid (HAX) after three hours of incubation at room temperature. The error bars represent the confidence intervals at 95% calculated using three measurements.</p

Interactions of Dissolved Organic Matter with Natural and Engineered Inorganic Colloids: A Review

This contribution critically reviews the state of knowledge on interactions of natural colloids and engineered nanoparticles with natural dissolved organic materials (DOM). These interactions determine the behavior and impact of colloids in natural system. Humic substances, polysaccharides, and proteins present in natural waters adsorb onto the surface of most colloids. We outline major adsorption mechanisms and structures of adsorption layers reported in the literature and discuss their generality on the basis of particle type, DOM type, and media composition. Advanced characterization methods of both DOM and colloids are needed to address insufficiently understood aspects as DOM fractionation upon adsorption, adsorption reversibility, and effect of capping agent. Precise knowledge on adsorption layer helps in predicting the colloidal stability of the sorbent. While humic substances tend to decrease aggregation and deposition through electrostatic and steric effects, bridging-flocculation can occur in the presence of multivalent cations. In the presence of DOM, aggregation may become reversible and aggregate structure dynamic. Nonetheless, the role of shear forces is still poorly understood. If traditional approaches based on the DLVO-theory can be useful in specific cases, quantitative aggregation models taking into account DOM dynamics, bridging, and disaggregation are needed for a comprehensive modeling of colloids stability in natural media

HDC-UVD-ICP-MS chromatograms of sunscreens extracts.

<p>HDC chromatograms of the colloids extracted from S1 (a and b) and S2 (c, d, and e). a and c: Titanium signal (three isotopes); b and e: UV-signal (absorption wavelength: 200 nm); d: Zinc signal (three isotopes). The time delay between the UVD and the ICP-MS detector was around 4 s.</p

Hydrodynamic Chromatography Coupled with Single Particle-Inductively Coupled Plasma Mass Spectrometry for Investigating Nanoparticles Agglomerates

Studying the environmental fate of engineered or natural colloids requires efficient methods for measuring their size and quantifying them in the environment. For example, an ideal method should maintain its correctness, accuracy, reproducibility, and robustness when applied to samples contained in complex matrixes and distinguish the target particles from the natural colloidal background signals. Since it is expected that a large portion of nanoparticles will form homo- or heteroagglomerates when released into environmental media, it is necessary to differentiate agglomerates from primary particles. At present, most sizing techniques do not fulfill these requirements. In this study, we used online coupling of two promising complementary sizing techniques: hydrodynamic chromatography (HDC) and single-particle ICPMS analysis to analyze gold nanoparticles agglomerated under controlled conditions. We used the single-particle mode of the ICPMS detector to detect single particles eluted from an HDC-column and determine a mass and an effective diameter for each particle using a double calibration approach. The average agglomerate relative density and fractal dimension were calculated using these data and used to follow the morphological evolution of agglomerates over time during the agglomeration process. The results demonstrate the ability of HDC coupled to single-particle analysis to identify and characterize nanoparticle homoagglomerates and is a very promising technique for the analysis of colloids in complex media