Phenanthroline method for quantitative determination of surface carboxyl groups on carboxylated polystyrene particles with high sensitivity

This study developed a phenanthroline method for quantitative determination of surface carboxyl groups on carboxylated polystyrene (PS-COOH) particles based on the coordination between the carboxyl groups and Fe2+. The ratio of the carboxyl groups, which is determined by conductometric titration method, to Fe2+ coordinated with the particles, which is determined by phenanthroline method, is 4.7, i.e. nCOOH = 4.7 × ΔnFe2+. The Lambert–Beer law is obeyed in the range of 0–60 × 10−9 mol/ml for the amount of surface carboxyl on the particles. The detection limit of the method is 2 nmol COOH/ml. The average standard deviation of the experiments is 4.4%. The relative deviation of the data obtained with this method is lower than 7% compared with that obtained with the conductometric titration method. The weight of the sample necessary for phenanthroline method is only about 0.1% of that necessary for conductometric titration method. It has been demonstrated that the phenanthroline method is suitable for quantitative determination of low amount of surface carboxyl groups on PS-COOH particles due to its high sensitivity. Copyright © 2009 John Wiley & Sons, Ltd.