Chromatographic studies of the structures of amorphous phosphates: a review

The technique of high-performance liquid chromatography (HPLC) has been used to investigate the distribution of phosphate anions in a variety of amorphous phosphate solids. In many cases, HPLC can be used to quantitatively measure the type and distribution of phosphate tetrahedral chains and rings in the solid that are between 1 and 10 nm in size. The experimental details of the HPLC technique are presented and the strengths and limitations of the technique are reviewed. The structural information obtained using HPLC is compared with structural information obtained using solid state techniques such as NMR and XPS. Several specific examples that illustrate the power and sensitivity of the HPLC technique are reviewed.