Novel titration method for surface-functionalised silica

▶ Novel aqueous based titration method. ▶ Titration method successful for amine, sulphonate, and carboxyl groups. ▶ Titration results are affected by sample mass. ▶ Titration results are affected by diffusion of reactant. This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH2-, SO3H- or COOH-functionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.