Publication details

Making good’s buffers good for freezing: The acidity changes and their elimination via mixing with sodium phosphate

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VESELÝ Lukáš BEHERA Susrisweta HEGER Dominik

Year of publication 2021
Type Article in Periodical
Magazine / Source International Journal of Pharmaceutics
MU Faculty or unit

Faculty of Science

Keywords pH shift; Cryopreservation; Stabilization; Freeze-concentrated solution; Sulfonephthalein indicators; Hammett acidity function; Cooling rate
Description Solutions of three Good’s buffers (HEPES, MOPS, and MES), both pure and mixed with sodium phosphate buffers (Na-P), are investigated in terms of the freezing-induced acidity changes in their operational pH ranges. The Good’s buffers have the tendency to basify upon freezing and, more intensively, at lower pHs. The acidity varies most prominently in MES, where the change may reach the value of two. Importantly, the Good’s buffers are shown to mitigate the strong acidification in the Na-P buffer. Diverse concentrations of the Good’s buffers are added to cancel out the strong, freezing-induced acidity drop in 50 mM Na-P that markedly contributes to the solution’s acidity; the relevant values are 3 mM HEPES, 10 mM MOPS, and 80 mM MES. These buffer blends are therefore proposed to be applied in maintaining approximately the acidity of solutions even after the freezing process and, as such, should limit the stresses for frozen chemicals and biochemicals.
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