The formula to calculate the isoelectric point of a substance is:
pI = (pKa + pKb) / 2
where:
pKa – Dissociation constant of acid;
pKb – Dissociation constant of base; and
pI – Isoelectric point.
So, to compute the isoelectric point:
First, you add the pKa and pKb values.
Then, divide the sum by 2.
The result is the isoelectric point.