Spherical Clay Conglomerates:  A Novel Stationary Phase for Solid-Phase Extraction and “Reversed-Phase” Liquid Chromatography

Abstract

A new solid phase is presented to be used for the solid-phase extraction (SPE) of organic compounds from aqueous solutions and as a stationary phase for the separation of organic compounds in "reversed-phase" HPLC. The material consists of spherical clay conglomerates (SCCs) in the size ranges of 2-5, 5-10, and 10-20 μm. SCCs are especially well suited for the extraction and separation of aromatic compounds with electron-withdrawing substituents, because of the formation of specific electron donor-acceptor (EDA) complexes of such compounds with natural clay minerals. A series of nitroaromatic compounds (NACs), e.g., nitrophenols, and nitrotoluenes, served as probe substances for the characterization of the SPE with SCCs online coupled to a C18-HPLC-DAD system. Breakthrough volumes were > 1 L and method detection limits (MDLs) < 100 ng/L for compounds with moderate to high affinity towards clay minerals. The performance of the material is hardly affected by matrix effects and because of its excellent physical properties, i.e., regenerability and pressure-resistance, it meets the requirements for fully automated routine trace analysis of several primary pollutants, such as 6-methyl-2,4-dinitrophenol (DNOC) or 2,4,6-trinitrotoluene (TNT), in various natural waters. Offline SPE with SCCs was superior or equivalent to commercial SPE products for analysis of such compounds. Finally, SCCs are shown to be well suited as a stationary phase in reversed-phase HPLC. This opens a wide range of applications, e.g., as an easy and fast separation technique that is orthogonal to C18 reversed-phase HPLC.

Concentrations and Mass Fluxes of Chloroacetic Acids and Trifluoroacetic Acid in Rain and Natural Waters in Switzerland

“…During this rain event, higher concentrations at 3.6 mm precipitation were due to fresh air masses from southern direction (change of wind direction). Note that rapid washout with the first few millimeters of rain, also called "first-flush" effect, was further observed for pesticides analyzed in the same rain event (31,32).…”

Solid-phase extraction using hierarchical organosilicates for enhanced detection of nitroenergetic targets

“…Other solid-phase extraction protocols have utilized a range of polymer materials and even clays in various formats providing preconcentration for ion mobility spectroscopy (IMS), [22][23][24] spectrophotometric, 11,25-27 and electrochemical 28 detection methods in addition to gas and liquid chromatography. [29][30][31][32][33][34][35][36] Porous organosilicate materials offer a class of sorbents with the potential to provide the preconcentration necessary for utilization of portable detection techniques. These materials are organic/inorganic hybrids synthesized through condensation of organic group bearing siloxane precursors around surfactant micelles.…”

Evaluation of β-Cyclodextrin Bonded Silica as a Selective Sorbent for the Solid-Phase Extraction of 4-Nitrophenol and 2,4-Dinitrophenol

“…Due to their easy generation processes, 2,3 they have raised even more concern in recent years, and many materials and methods have been developed for their analysis. [4][5][6][7][8][9] As a widely used sample pretreatment method, solid-phase extraction (SPE) has been introduced to determine polar analytes both in their on-line and off-line modes. [7][8][9][10] Nitrophenols belong to this kind of compound and many new materials have been developed for facilitating their trace enrichment.…”