Diamond particles have been functionalized in our laboratories to produce amino, C18, perfluoro, phenyl, and sulfonic acid stationary phases for liquid chromatography and solid phase extraction. Stability tests on these phases indicate that they are stable for many hours in 2.5 M HCl or 2.5 M NaOH. Two general strategies have been explored for making these stationary phases. In one, hydrogen-terminated diamond has been reacted with a mixture of a radical initiator and monomers to produce bonded ca. 3 – 6 nm polymer films in a single step. In the second, self-limiting polymer adsorption has been employed to make phases that also have thicknesses of nanometer dimensions. For example, poly(allylamine) adsorbs in this manner to produce an amino phase, which upon crosslinking with a diepoxide creates an extremely stable phase. The expected surface chemistries have been confirmed by X-ray photoelectron spectroscopy, FTIR, time-of-flight secondary ion mass spectrometry, and on model, planar, silicon surfaces using spectroscopic ellipsometry and wetting. Solid phase extraction has been successfully performed on the amino, sulfonic acid, and C18 phases. HPLC is demonstrated using ca. 5 micron diamond particles with high surface areas. Monolithic diamond materials have also been prepared by pressing diamond powder with a cobalt catalyst, followed by removal of the catalyst to yield a porous solid.