Flow field-flow fractionation-inductively coupled plasma mass spectrometry for sediment bound trace metal characterization

Coupling the gentle size fractionation capability of flow field-flow fractionation (flow FFF) to a sensitive element detector like inductively coupled plasma mass spectrometry (ICP-MS) facilitates the determination of trace metals bound to various size fractions of colloidal and particulate materials. Organic matter in river sediment core samples was extracted by sodium pyrophosphate, and extracted solutions were introduced into the FFF channel for size separation and subsequently elemental detection by ICP-MS. The distributions of Cu, Fe, Mn, Pb, Sr, Ti and Zn with core depth (0-40 cm) and hydrodynamic diameter are obtained. Most trace metals are bound to the 10-15 cm sediment layer and 2-6 nm (fulvic and humic acids) macromolecules. Crude fulvic and humic acids also were isolated by adjusting the pH of the extracted solutions. Trace metals associated with sediment core samples also were extracted selectively by acetic acid and hydroxylamine hydrochloride to leach exchangeable and reducible fractions, respectively, before sodium pyrophosphate extraction. Results show that Pb is readily exchangeable and Mn is reducible as well as exchangeable, whereas Ti is inert and thought to present as fine colloidal minerals. This study illustrates the range of physicochemical information that can be gained using flow FFF-ICP-MS for environmental investigations.