In this work, the partitioning of four N-(2,4-dinitrophenyl)-amino acids (DNP-L-leucine, DNP-L-valine, DNP-L-alanine, and DNP-glycine) in aqueous two-phase systems (ATPS) containing a new biodegradable ionic liquid cholinium alaninate, [Ch] [Ala], and the inorganic salts K3PO4 and K2HPO4 was determined at T = 298.15 K and p = 101.3 kPa. The influence of the salt on the partition coefficients was discussed. The distribution coefficients (K) of the four studied DNP-amino acids are higher in the ATPS containing the inorganic salt K3PO4. Moreover, the experimental LLE data obtained for both ATPS {[Ch] [Ala] (1) + K3PO4 or K2HPO4 (2) + water (3)} (previously reported) were represented using the nonrandom two-liquid thermodynamic model. Finally, a comparison of the distribution coefficients presented in this work and those found in literature for the four studied DNP-amino acids on different ATPS was performed.