Spherical clay conglomerates: A novel stationary phase for solid phase extraction and "reversed-phase" liquid chromatography

A new solid phase is presented to be used for the solid-phase extraction (S PE) of organic compounds from aqueous solutions and as a stationary phase f or the separation of organic compounds in "reversed-phase" HPLC, The materi al consists of spherical clay conglomerates (SCCs) in the size ranges of 2- 5, 5-10, and 10-20 mu m. SCCs are especially well suited for the extraction and separation of aromatic compounds with electron-withdrawing substituent s, because of the formation of specific electron donor-acceptor (EDA) compl exes of such compounds with natural clay minerals. A series of nitroaromati c 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 towa rds clay minerals. The performance of the material is hardly affected by ma trix: effects and because of its excellent physical properties, i.e., regen erability and pressure-resistance, it meets the requirements for fully auto mated routine trace analysis of several primary pollutants, such as 6-methy l-2,4-dinitrophenol (DNOC) or 2,4,6-trinitrotoluene (TNT), ia various natur al waters, Offline SPE with SCCs was superior or equivalent to commercial S PE products for analysis of such compounds. Finally, SCCs are shown to be w ell 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.