2004 Volume 53 Issue 10 Pages 1125-1131
A method based on proton nuclear magnetic resonance (1H-NMR) using an internal standard (IS) was developed for the determination of anionic and cationic surfactants. In this study, potassium hydrogen phthalate or sodium 3-trimethylsilyl-2,2,3,3-tetradeutero propionic acid was added to a sample solution as an IS for the determination, and surfactants were determined by using integrations of IS and diagnostic surfactant resonances in the 1H-NMR spectrum. This method is suitable for the determination of surfactants because there is no surfactant whose contribution corresponds completely with each analyte in many cases. By optimizing the acquisition parameters and solvent, various surfactants were determined under the same condition. Each 1H-NMR spectrum was obtained within 5 min and the detection limit given for sodium lauryl sulfate, a typical anionic surfactant, was approximately 60 ppm. The results obtained for commercial surfactants were in good agreement with those of the JIS titration method (Epton method) and the relative standard deviations were 0.12∼0.44%.
