Ionic characterization of a synthetic amphoteric surfactant: N,N-((butyloxy)propyl) amino diacetic acid

N,N-((Butyloxy)propyl)amino diacetic acid is an amphoteric surfactant of the glycinate family. The synthesis of this glycinate was achieved via the ester route to obtain a pure compound. The infrared (IR) spectra of the aqueous solutions of this compound were obtained in the pH range 0.2-14 in order to determine the ionic distribution of the molecule as a function of pH. After subtracting the water bands in the IR spectra, factor analysis (FA) was used to separate the spectra of the ionic species and determine their abundance. The pK(a)'s were retrieved from the volumetric titration as a function of pH. The values were used to calculate the volumetric abundance of each ionic species as a function of pH. The distribution curves thus obtained were compared with the normalized distribution curves obtained from the IR data. There is a good agreement between the two curves. The following species were obtained for the glycinate in water: the cation (pH 0-3.4), the zwitterion (pH 0-5.4), the monocarboxylate (pH 1-12), and the dicarboxylate (pH 7-14).