Sustainable development and environmental analysis

From Impure to Purified Silver Nanoparticles: Advances and Timeline in Separation Methods

“…Thus, cloud-point extraction (CPE) is based on the solubilization ability and on the cloud points of non-ionic surfactants. It is considered an approach for the separation, extraction, and preconcentration of trace elements, before their determination [57], such as for beryllium and chromium in water samples [58], silver in environmental waters [59], cobalt in water and food samples [60], and cadmium, copper, and lead in biological fluids [61], among others. The extraction protocol for trace elements is based on three steps.…”

“…At the cloud-point, the solution with the surfactant becomes turbid, and it is separated into two distinct phases (the surfactant-rich phase and a dilute aqueous phase). The analytes separated in the surfactant-rich phase can then be extracted and concentrated, due to the analyte-micelle interaction [1,57]. In the case of separation of AgNPs, the addition of some salts, such as NaNO 3 or Na 2 S 2 O 3 , improves the separation of the phases and increases the efficiency of the extraction.…”

“…For the detection of Ag + through colorimetric assay after CPE, the supernatant was discarded, and an amount of H2O2 was added to the concen- CPE is also a method of choice for extracting pollutants (e.g., metal NPs) from environmental and biological samples, without modifying their sizes and shapes. It is a simple, low-cost, and environment-friendly technique, which has a high capacity to concentrate trace elements [57]. Nevertheless, a limitation of this method is the low extraction efficacy when the analytes are protein-coated NPs, like AgNPs functionalized with BSA.…”

Cloud Point Extraction as a Method for Preconcentration of Metal Ions

“…The use of micellar systems, in methods such as CPE, has attracted considerable attention in recent years mainly because it is in line with the principles of "green chemistry" (Rasoolzadeh, Hashemi, & Serenjeh 2017). Green chemistry can be defined as a set of procedures to reduce or eliminate the use or generation of toxic substances for human health and the environment (Hussain & Keçili 2020). CPE is a "green" method due to the fact that, as an extractor, it uses dilute solutions of surfactants that are less toxic than classical organic solvents used in liquid-liquid extraction.…”