Asymmetrical flow field-flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, was tested for stability studies of dispersions of citrate-capped silver nanoparticles (AgNPs) in several water matrices. The main goal is to provide knowledge to understand their possible behavior in the environment for short times since mixturing (up to 180 min). Ultrapure (UPW), bottled (BW1, BW2), tap (TW), transitional (TrW) and sea water (SW) matrices were assayed. Observations were compatible with the aggregation of AgNPs, a change in the plasmon band and a size growth with time were done. Fractograms showed different evolution fingerprints in the function of the waters and batches. The aggregation rate order was BW2, SW, TrW, BW1 and TW, being BW2 the lowest and TW the highest. NP aggregation can be induced by increasing the salt concentration of the medium, however transitional and sea waters did not follow the rule. Both matrices presented a lower aggregation rate in comparison with other aqueous matrices with much lower ionic strength (BW1 and TW), which can be explained by the potential presence of dissolved organic matter and/or the high concentration of halides providing their stabilization and passivation, respectively. AF4 provides relevant information with respect to static DLS and UV-Vis Spectroscopy showing that at least two populations of aggregates with different sizes between them, depending on both, the mixture time for a given matrix and type of water matrix for the same time.

Among different nanomaterials, gold and silver nanoparticles (AuNPs and AgNPs) have become useful tools for a wide variety of applications in general, and particularly for plasmonic assays. Particle size and stability analysis are key elements for their practical applications since the NPs properties depend on these parameters. Hence, in the present work, asymmetrical flow field flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, has been evaluated for stability studies of citrate-capped AuNPs and AgNPs aqueous dispersions. First, experimental parameters, such as mobile phase or cross-flow rate were optimized. Sodium azide to pH 7 for AuNPs and pH 9.2 for AgNPs were selected as the optimum mobile phase. The analytical response of bulk dispersions of AuNPs (20, 40, 60 and 80 nm) and AgNPs (20, 40 and 60 nm) and their dilutions have been studied. Fractograms showed a decrease on the absorbance signal in diluted dispersions as a function of time and particle size for the diluted dispersions that can be explained by dissolution in diluted dispersion since hydrodynamic diameter was constant. The results indicated that the dependence of the signal with time was more intense for AgNPs than for AuNPs, which can be correlated with its lower stability. These findings should be considered when plasmonic assays are realized. Here, assays involving non-oxidant acidic acids as use cases, were tested for several batches of NPs and considerations about their stability and operability stablished.

The use of current metric tools for sample preparation has proven highly valuable in identifying the strengths and weaknesses of various analytical approaches. However, as Analytical Sciences increasingly move towards sustainability, it becomes evident that existing metrics may not fully cover all the dimensions required for a comprehensive assessment. An overview to encourage the evolution towards more advanced metric tools for sample preparation by reflecting on which parameters should be evaluated and on the principles that ought to guide their design. The tutorial highlights the need for new or improved metrics capable and identify the most relevant criteria and how they can be integrated. The discussion is particularly focused in the context of miniaturization and the development of new extractive materials. Through case studies, solvents and sorbents are examined using analytical performance, green, and market-related criteria, emphasizing the importance of integrating these perspectives into future tools. Solid-phase (SPME) and liquid-phase microextraction (LPME) are evaluated using the metric tools currently available, pointing out the challenges associated with the application. The results reveal the need to advance towards more advanced metric tools contextualizing the outcomes within the complexity of the analytical problem. This manuscript highlight the need to advance metric tools towards models capable of integrating environmental, analytical, and practical dimensions within a coherent sustainability-oriented framework. The tutorial offers guidance for researchers and developers aiming to create more effective tools for the design and evaluation of sample preparation methods, tools that not only address greenness but also deliver greater robustness, relevance, and applicability in real analytical scenarios.

An improved and more sustainable waste management system is required for successful development of technologies based on renewable sources. Rice straw is submitted to controlled combustion reactions and the produced ashes are chemically treated to produce silica. After a chemical activation step, the activated silica shows potential as an adsorbent agent and will be used to remove the excess of nitrates in groundwater and wells in the area of Alginet (Valencia, Spain), selected as a vulnerable zone within the Nitrates Directive. The demonstration activity aims to have a local impact on municipalities of 200 inhabitants or fewer, decreasing from current nitrate concentrations close to 50 mg/L, to a target of 25 mg/L. In a successive step, the methodology will be transferred to other municipalities with similar nitrate problems (Piemonte, Italy) and replicated to remove different pollutants such as manure (the Netherlands) and waste waters from the textile industry (Italy).

The release of engineered nanoparticles (ENPs) into the environment is an emerging concern with significant implications for organism exposure due to the possible toxicity caused by these materials. Understanding the dissolution and transformation of silver nanoparticles (AgNPs) under dynamic flow conditions is critical, as these processes directly govern the mobility, persistence, and bioavailability of this material in natural aquatic systems, ultimately influencing its ecological risk and environmental impact. In this work, a methodology based on continuous- flow systems to assess the dissolution and transformation behavior of nanomaterials (NMs) under environmentally relevant conditions has been applied specifically to AgNPs. In this way, AgNPs nanopowder has been analyzed employing different environmental conditions (presence of oxygen, background electrolyte, types of buffers and NOM,). Results confirmed the expected dependency of AgNPs dissolution on the oxygen availability, corroborating previous batch assays. The evaluation of the AgNPs sulfidation in oxic and anoxic regimes were applied under different flow rates. AgNPs sulfidation is a complex process that takes place in two steps, oxidation followed by the AgS formation. Two different sulfide compounds with different solubilities can be formed: amorphous AgxSy which is related to an elevated Ag ion release, and high ordered Ag_xS_y phase which create a protective layer that reduces the ion release. Overall, the proposed continuous-flow methodology offers a reliable tool to investigate the dissolution and transformation of ENPS under environmentally relevant conditions. It provides valuable insights into the mechanisms that govern nanoparticles behavior, particularity during the initial stages of reaction.