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Investigating freezing-induced acidity changes in citrate buffers.

Behera, Susrisweta, Veselý, Lukáš, Štůsek, Radim, Hauptmann, Astrid, Loerting, Thomas and Heger, Dominik (2023) Investigating freezing-induced acidity changes in citrate buffers. International journal of pharmaceutics, 643. p. 123211. ISSN 1873-3476


Citrate buffers are commonly utilized in the field of biomolecule stabilization. We investigate their applicability in the frozen state within a range of initial pHs (2.5 to 8.0) and concentrations (0.02 to 0.60 M). Citrate buffer solutions subjected to various cooling and heating temperatures are examined in terms of the freezing-induced acidity changes, revealing that citrate buffers acidify upon cooling. The acidity is assessed with sulfonephthalein molecular probes frozen in the samples. Optical cryomicroscopy combined with differential scanning calorimetry was employed to investigate the causes of the observed acidity changes. The buffers partly crystallize and partly vitrify in the ice matrix; these processes influence the resulting pH and allow designing the optimal storage temperatures in the frozen state. The freezing-induced acidification apparently depends on the buffer concentration; at each pH, we suggest pertinent concentration, at which freezing causes minimal acidification.

Item Type: Article
Keywords: Freezing Buffers Hydrogen-Ion Concentration Freeze Drying Citrates Calorimetry, Differential Scanning
Date Deposited: 12 Dec 2023 00:45
Last Modified: 12 Dec 2023 00:45