COMPLEXATION BETWEEN BENZOIC-ACID AND FATTY AMINES - AN ADSORPTION AND CHEMOMETRIC STUDY

Interactions between benzoic acid and octyl amine have been studied by means of chemometric methods, i.e. PCA score plot and rank analysis a nd by adsorption onto solid alpha-alumina without and with 0.1M NaCl a nd with pH adjusted to 4.2 or 3.95. The chemometric study reveals that a benzoic acid/octyl amine complex exist at the pK(a) value of benzoi c acid. The adsorption isotherms show that a decomplexation occurs whe n the complex is in contact with solid alpha-alumina. It is only the b enzoate ion that adsorbs onto the solid surface. Without added electro lyte, the shape of the isotherm is of L type and benzoate ion is found to occupy about 0.59 nm(2) on the surface. In the presence of NaCl, b enzoate ion occupies 4.91 nm(2) on alumina. In this case the adsorptio n isotherms can be classified as S isotherms. The reduction in adsorpt ion capacity can be explained by the electrostatic shielding of the su rface sites with the electrolyte. (C) 1997 Elsevier Science B.V.