Effect of choline-based ionic liquids on thermodynamic and transport properties of aqueous diphenhydramine hydrochloric acid solutions

Abstract

In this work, to investigate a possible interactions between diphenhydramine hydrochloric acid [DPH-HCl] and two ionic liquids (ILs) (choline bi-tartrate [Ch][bit] and choline lactate [Ch][Lac]) the isopiestic measurements were carried out on the aqueous systems containing (choline bi-tartrate + diphenhydramine hydrochloric acid) and (choline lactate + diphenhydramine hydrochloric acid) and the corresponding binary solutions at 298.15 K. The obtained experimental water activity data were fitted to the generalized polynomial equation from which activity coefficients of the drug and ionic liquids were calculated. The negative deviation of water isoactivity lines from the semi-ideal solution and positive transfer Gibbs energy values calculated from activity coefficients of ternary and binary solutions indicate that there are unfavorable interactions between both of ILs and the drug.Density, speed of sound and viscosity of the above ternary and binary solutions have also been measured at T=(288.15 to 318.15 K) from which respectively apparent molar volume, apparent molar compressibility, viscosity B-coefficient values and the corresponding transfer values from binary to ternary solutions have been calculated. The negative transfer molar volumes imply unfavorable interactions between both of ILs and the drug which is consistent with the isopiestic results. These data were also used to obtain some information on the effect of temperature and concentration of ionic liquids on the ILs-drug interactions. The more negative transfer molar volume at higher concentrations of ILs indicates that these interactions are more weakened by increasing of both of ionic liquids concentrations.