Hydroxyapatite

Hydroxyapatite (HA) has become one of the best characterized multimodal chromatography media in existence, with valuable research and industrial applications throughout the field of bioprocessing. Its combination of cation exchange and calcium-affinity mechanisms have given it the ability to achieve separations that no other chromatography media can match, and it continues to provide unique solutions for emerging challenges in the field.  

HA is a naturally occurring crystalline compound with the structural formula of Ca5(PO4)3OH. Its formula creates an impression that calcium residues are the dominant feature of the crystal surfaces, but most of them are involved in maintaining subsurface structure. This leaves phosphate residues as the dominant surface feature. Instead of the 5:3 Ca:P ratio that might be expected, surface ratios average closer to 1:6.

Applications
HA is specifically developed for the purification of biological samples, such as antibodies and DNA, the separation of impurities from the native antibody (intact/monomer) and the isolation of single-stranded from double-stranded DNA.