The present invention relates to novel amphoteric ion exchangers which possess not only phthalamide groups of the formula (I) but also —(CH2)mNR1R2 groups and/or if appropriate —(CH2)mNR1R2R3 groups, wherein m is an integer from 1 to 4 and R1, R2, R3 in each case independently of one another are hydrogen, —CH3, —CH2CH3, —CH2CH2CH3, benzyl, —OCH2CH3 or —CH2CH2OH and X is H or Na or K, to a process for production thereof and also use thereof.