pH transients in hydroxyapatite chromatography columns-Effects of operating conditions and media properties.

pH transitions occur in hydroxyapatite (HAP) columns that are subject to step changes in salt concentration, which have been shown to be controlled by proton exchange on the HAP surface. The pH temporarily decreases before gradually returning to the feed value when the salt concentration increases, potentially compromising the stability of the HAP when either the magnitude or duration of the pH drop is excessive. The opposite happens when the salt concentration decreases.

pH Transients in hydroxyapatite chromatography columns-experimental evidence and phenomenological modeling.

Hydroxyapatite (HAP) columns, widely used for chromatographic separation of proteins and other biomolecules because of their unique selectivity and ability to resolve complex mixtures, exhibit limited stability at acidic conditions requiring careful control of pH. Even with buffered solutions, however, unintended pH transients can occur when the salt concentration varies. For example, the pH temporarily decreases below the feed value when the salt concentration increases and increases above the feed value when the salt concentration is decreased.