Solubility of Monoalkyl Phophate in Water in the Presence of Arginine and Triton, and Solubilization of Methyl Yellow Through the Mixed Micelle

Abstract

Effects of arginine (Arg) and Triton such as Triton-X (TX) and Triton-N (TN) on the solubility of monoalkyl phosphoric acid (MAP) such as dodecyl (DP), myristyl (MP), and cetyl phosphoric acid (CP) in an aqueous phase were studied. Although these MAPs are scarcely soluble in water, their solubility at 70 o C increased with a concentration of Triton added. The effect of TN was stronger than that of TX. DP became soluble at room temperature when Arg was added up to the mixing ratio of Arg/DP = 3 in mole. MP and CP were hardly soluble yet in the presence of Arg alone while these became soluble after adding Triton together with Arg. Their acidic head group was ionized by Arg, resulting in an increase in its affinity for water. DP was soluble just after the ionization while MP and CP were soluble after the ionization and concomitant formation of the mixed micelle with the Triton added. Methyl yellow, barely soluble in water, was solubilized after entrapment into the mixed micelle. Its solubility increased with a concentration and chain length of the MAP added as a solubilizing agent.