A process for purifying a mixture comprising monoethylene glycol, monoethanolamine, ethylenediamine and diethylenetriamine (DETA), and low boilers having a boiling point not higher than piperazine and high boilers having a boiling point not lower than aminoethylethanolamine (AEEA), wherein the process comprises the following steps: a) separating a mixture comprising MEG, MEA, EDA and DETA, and low boilers having a boiling point not higher than PIP and high boilers having a boiling point not lower than AEEA, into (i) a mixture A comprising EDA and the low boilers having a boiling point not higher than PIP; and (ii) a mixture B comprising MEA; and (iii) a mixture C comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; b) separating mixture C from stage a) into (i) a mixture D comprising MEG; and (ii) a mixture E comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; c) separating mixture E from stage b) either into (i) a mixture F comprising MEG and DETA; and (ii) a mixture G comprising the high boilers having a boiling point not lower than AEEA; or into (i) a mixture F comprising MEG and DETA; and (ii) a mixture G1 comprising AEEA; and (iii) a mixture G2 comprising the high boilers having a boiling point higher than AEEA; d) separating mixture F from stage c) by extractive distillation with triethylene glycol into (i) a mixture H comprising MEG; and (ii) a mixture I comprising DETA and TEG. a) separating a mixture comprising MEG, MEA, EDA and DETA, and low boilers having a boiling point not higher than PIP and high boilers having a boiling point not lower than AEEA, into (i) a mixture A comprising EDA and the low boilers having a boiling point not higher than PIP; and (ii) a mixture B comprising MEA; and (iii) a mixture C comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; (i) a mixture A comprising EDA and the low boilers having a boiling point not higher than PIP; and (ii) a mixture B comprising MEA; and (iii) a mixture C comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; b) separating mixture C from stage a) into (i) a mixture D comprising MEG; and (ii) a mixture E comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; (i) a mixture D comprising MEG; and (ii) a mixture E comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; c) separating mixture E from stage b) either into (i) a mixture F comprising MEG and DETA; and (ii) a mixture G comprising the high boilers having a boiling point not lower than AEEA; or into (i) a mixture F comprising MEG and DETA; and (ii) a mixture G1 comprising AEEA; and (iii) a mixture G2 comprising the high boilers having a boiling point higher than AEEA; (i) a mixture F comprising MEG and DETA; and (ii) a mixture G comprising the high boilers having a boiling point not lower than AEEA; or into (i) a mixture F comprising MEG and DETA; and (ii) a mixture G1 comprising AEEA; and (iii) a mixture G2 comprising the high boilers having a boiling point higher than AEEA; d) separating mixture F from stage c) by extractive distillation with triethylene glycol into (i) a mixture H comprising MEG; and (ii) a mixture I comprising DETA and TEG. (i) a mixture H comprising MEG; and (ii) a mixture I comprising DETA and TEG.