title: Can cloud point-based enrichment, preservation, and detection methods help to bridge gaps in aquatic nanometrology?
abstract: Coacervate-based techniques are intensively used in environmental analytical chemistry to enrich and extract different kinds of analytes. Most methods focus on the total content or the speciation of inorganic and organic substances. Size fractionation is less commonly addressed. Within coacervate-based techniques, cloud point extraction (CPE) is characterized by a phase separation of non-ionic surfactants dispersed in an aqueous solution when the respective cloud point temperature is exceeded. In this context, the feature article raises the following question: May CPE in future studies serve as a key tool (i) to enrich and extract nanoparticles (NPs) from complex environmental matrices prior to analyses and (ii) to preserve the colloidal status of unstable environmental samples? With respect to engineered NPs, a significant gap between environmental concentrations and size- and element-specific analytical capabilities is still visible. CPE may support efforts to overcome this "concentration gap" via the analyte enrichment. In addition, most environmental colloidal systems are known to be unstable, dynamic, and sensitive to changes of the environmental conditions during sampling and sample preparation. This delivers a so far unsolved "sample preparation dilemma" in the analytical process. The authors are of the opinion that CPE-based methods have the potential to preserve the colloidal status of these instable samples. Focusing on NPs, this feature article aims to support the discussion on the creation of a convention called the "CPE extractable fraction" by connecting current knowledge on CPE mechanisms and on available applications, via the uncertainties visible and modeling approaches available, with potential future benefits from CPE protocols.
authors: Department G2-Aquatic Chemistry, Federal Institute of Hydrology, Am Mainzer Tor 1, 56068, Koblenz, Germany. duester@bafg.de.
authors: Lars
authors: L
authors: Duester
authors: Department G2-Aquatic Chemistry, Federal Institute of Hydrology, Am Mainzer Tor 1, 56068, Koblenz, Germany.
authors: Anne-Lena
authors: AL
authors: Fabricius
authors: Thermal and Separation Processes, Hamburg University of Technology, Eißendorfer Straße 38, 21073, Hamburg, Germany.
authors: Sven
authors: S
authors: Jakobtorweihen
authors: Environmental Chemistry, University of Koblenz-Landau, Fortstraße 7, 76829, Landau, Germany.
authors: Allan
authors: A
authors: Philippe
authors: Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, 85747, Garching, Germany.
authors: Florian
authors: F
authors: Weigl
authors: Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, 85747, Garching, Germany.
authors: Andreas
authors: A
authors: Wimmer
authors: Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, 85747, Garching, Germany.
authors: Michael
authors: M
authors: Schuster
authors: Department of Chemistry, University of Gujrat, Gujrat, 50700, Pakistan.
authors: Muhammad Faizan
authors: MF
authors: Nazar
keywords: Cloud point extraction; Coacervate-based techniques; Colloids; Enrichment; Nanoparticles; Sample preservation