Determination of Some Tertiary Amines as π-Complexes with Tetracyanoethylene

Abstract

Some tertiary amines were determined by measurement of the absorbance of their π-complex (I) with tetracyanoethylene (TCNE) as a function of time. The initial absorbance values of I formed (corresponding to the added concentrations of tertiary amines) were calculated by a numerical method with a pseudo first-order rate equation for the decomposition of I using the rate constant and the absorbance values as a function of time. Calibration plots gave good straight lines for each tertiary amine. The average errors of determination were from -1.23% to +3.03% and the relative standard deviations were less than 1.82% (n=3). The recovery of each amine was from 98.0% to 103.0%. For mixtures of primary, secondary and tertiary amines, the interference of primary and secondary amines could be eliminated by addition of acetic anhydride before the reaction with TCNE. The average errors of determination were from -2.96% to +5.79% and the relative standard deviations were less than 1.15% (n=3). The recovery of each tertiary amine was from 97.0% to 105.8%. The presented method is accurate, rapid and highly sensitive for many tertiary amines.