Improved, high-throughput approach for phosphorus speciation in natural sediments via the sedex sequential extraction method

A novel approach for implementation of sequential extraction methods using a multisample, solid-phase extraction manifold (SPExMan) successfully addresses several chronic problems typical of sequential extraction methods, including (1) sample loss during supernatant removal and (2) the time-and work-intensive nature of sequential extraction protocols. Supernatant is removed from SPExMan reaction vessels through an integrated filter base, eliminating the possibility of sample loss during supernatant collection. Vacuum manifold filtration makes it possible to filter multiple samples simultaneously. These two features of the design result in minimal residual volume between steps, eliminating the need for wash steps in between principle extraction steps and for residual volume correction. The SPExMan system was evaluated for the SEDEX method of quantifying different forms of phosphorus in sediments. Results from three different sediment samples analyzed via the classical centrifuge/syringe filtration SEDEX method and the SPExMan-SEDEX method agree well, indicating that the SPExMan design is robust for performance of sequential extraction methods, and that SPExMan-SEDEX data can be directly compared with classical SEDEX data. Overall, sample throughput is greatly increased by the SPExMan approach. Materials chosen for the SPExMan system are compatible with a wide range of chemical extractants, including corrosives and organic solvents.