Conductometric analysis of 1-butyl-3-methylimidazolium ibuprofenate as an active pharmaceutical ingredient ionic liquid (API-IL) in the aqueous amino acids solutions

• The novel API-IL, 1-butyl-3-methylimidazolium ibuprofenate was synthesized.
• The specific electrical conductivities of the synthesized AP-IL have been measured at several temperatures.
• The effect of two amino acids, glycine and l-alanine on the molar conductivity of the API-IL has been investigated.
• The ion association constants and limiting molar conductivities of [BMIM][Ibu] in amino acids solutions decrease as the concentration and temperature increase.
• The ion association process in l-alanine take place more spontaneously relative to glycine.

In this work, electrical conductivities of the active pharmaceutical ingredient in ionic liquid form (API-IL), 1-butyl-3-methylimidazolium ibuprofenate, [BMIM][Ibu] in water and in the aqueous solutions of amino acids, glycine and l-alanine have been measured at T = (288.15–318.15) K. The calculated molar conductivity data were analyzed by two famous conductivity models, low concentration Chemical Model (lcCM) and Fernandez-Prini (FP). The results show that the FP equation is more appropriate for analysis of the molar conductivity data because the calculated parameters are not highly influenced by the initial guess values of the parameters. Using these models, the limiting molar conductivities (Λ0Λ0), ion association constants (KAKA) and standard Gibbs energy (ΔGA0) for the ion association process of the API-IL have been calculated. The values of Λ0Λ0 and KAKA decrease as the concentration of amino acid increase. This trend may be attributed to low mobility of the ions with large radii produced during the solvation of the ions by zwitterions of the amino acids. The values of Λ0Λ0 and KAKA also increase from glycine to l-alanine solutions. The ions of [BMIM][Ibu] are more solvated by (COO−/NH3+) zwitterionic centers of glycine rather than l-alanine. The more negative values of ΔGA0 for [BMIM][Ibu] in l-alanine rather than glycine solutions indicates that more spontaneously and more feasibility of the ion association process in this amino acid.

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