Newly developed flow field-flow fractionation-inductively coupled plasma mass spectrometry (FlFFF-ICP-MS) has been explored for its capability of size-based elemental speciation. Information obtained from this combination technique includes size and molecular weight distributions, diffusion coefficient, polydispersity, and molecular conformation. Various biological, environmental, and industrial samples are examined to illustrate the versatility of FlFFF-ICP-MS.
For biological applications complexation of metals (Co, Cr, Fe, La, Th, and U) with three important proteins (albumin, ferritin, and transferrin) is examined. Size characterization of elements (Al, Cu, Pb, and Zn) in food macromolecules also is investigated.
For environmental applications elemental size characterization of Al, Cu, Pb and Zn in humic acids is examined. Physical parameters such as diffusion coefficient and hydrodynamic diameter are determined. Furthermore, FlFFF is employed to study the aggregation of humic acid in the presence of alkaline earth ions (Ca, Sr, and Ba). An equivalent sphere density index (DESI) is proposed and used to trace the conformational arrangement of humic macromolecules. In addition, the FlFFF-ICP-MS is used for elemental size characterization of river and estuarine sediment core samples and aquatic colloids.
To demonstrate the scope of the FlFFF-ICP-MS technique with industrial materials, size characterization of Al, Fe, Pb, Si, Ti, and Zr in various chemical mechanical polishing slurries is examined. Particle size information, including size distribution, minimum and maximum particle sizes, average and mean diameters, polydispersity, and breadth of distribution are obtained.
Owing to the similarity of FlFFF and a membrane filtration technique, a preliminary investigation of applying a FlFFF channel as an on-channel matrix removal and analyte preconcentration before ICP-MS detection is carried out. Various analyte elements are approximately 50-fold preconcentrated and matrix-removed from 5,000 mg l -1 Ca and Na salt solutions.
Frit outlet preconcentration after FlFFF size separation also is examined. With a frit outlet, a standard cross flow nebulizer does not maintain the added benefit from the FlFFF frit outlet. Therefore, use of micronebulizer is necessary for ICP-MS detection and is evaluated in this study.
