The determination of unreacted amines in long chain amine oxides by potentiometric titration

Abstract

During the manufacture of amine oxides information on the amount of unreacted tertiary amine present is needed in order to follow the reaction. A number of analytical procedures have been devised to obtain this information. Wet methods include redox titrations of the amine oxide and differential titrations using derivatization of the amine or amine oxide. Various chromatographic procedures using GC, TLC and HPLC also have been reported. All of these procedures have some limitations. A simple, rapid, quality control procedure would be useful. A rapid, nonaqueous titration procedure has been developed in our laboratory that makes use of the “anomalous salt” behavior of amine oxides. A modified solvent and titrant is used to obtain two potential breaks in the titration. The first break corresponds to half of the amine oxide. The second break represents the second half of the amine oxide plus any unreacted amine. With this information the amine oxide and unreacted amines can be calculated. The precision and accuracy of the titration have been studied using samples spiked with known amounts of amine.