If the acidic group is titrating with NaOH and the basic group with HCI, the pK of the -COOH group is 9.6 and that of the -NH2 group is 2.34.

• 如果酸性基团用NaOH滴定；并且碱基用COOH滴定；-COOH的pk值为9.；6；-NH2基是2