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Physical & Chemical properties

Dissociation constant

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Description of key information

It can be determined that the test item would always be ionised at environmentally relevant pH’s.

Key value for chemical safety assessment

Additional information

Experimental testing was not possible due to low purity and the presence of overlapping dissociation constants. Estimates of dissociation constants were therefore obtained using computer based estimation software, Advanced Chemistry Development I-Lab Web Service (ACD I-Lab 2.0). 

The following dissociation constants were obtained:

Table 13.2

Functional Group

Dissociation Constants

Six P-OH groups
(systematic ionisation of the first and then second hydroxyl group on each of the three phosphate groups)

1.25±0.10
1.63
±0.10
1.91
±0.10
6.24
±0.30
6.51
±0.30
6.89
±0.30

Tertiary amine group

5.89±0.50

From these results, it can be determined that the test item would always be ionised at environmentally relevant pH’s.