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Physical & Chemical properties

Dissociation constant

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Description of key information

The pKa of the test material has been measured as 3.4

Key value for chemical safety assessment

pKa at 20°C:
3.4

Additional information

In a GLP study conducted according to OECD Guideline 112, the dissociation constant (pKa) of the test material was determined by a spectrophotometric method. The value was checked against that obtained from a simple titration of the potassium salt with dilute hydrochloric acid. For the spectrophotometric method, solutions of the test material in formate buffer (approx. 20 mg/mL) were scanned and the concentration of the ionised and neutral (unionised) fraction determined.

The mean pKa value of 3.4 was calculated from 4 spectrophotometric determinations at pH values between 3.11 and 3.82. Using the titration method, the pKa was found to be between 3.2 and 4.2, supporting the spectrophotometric value of 3.4.