Spectrophotometric determination of longchain aliphatic amines with chrome-azurol S-aluminum chelate

Abstract

The precipitation of ternary complex of chromeazurol S, Al (III) and long-chain aliphatic amine was avoided by adding 20 % ethanol, and the solution was submitted to a spectrophotometric determination of the amines. The reagent solution was fixed as 3: 2 mixture of 1.0×10-4M chrome-azurol S in ethanol and 1.5×10-4M aluminum potassium sulfate in pH 4.8 Walpole buffer, and 5 ml reagent solution was added into 10 ml sample solution. After standing for 20 min, the absorbance was measured at 640 nm against a reagent blank. In the case of octadecylamine (ODA), Bee's low held from 2.5 to 10.0 µg/ml, the ε value and coefficient of variation being 1.85×104 1 mol-1 cm-1 and 0.86 % for 10 µg/ml, respectively. This method was applied to n-butyl-n-octadecylamine, diethyl-n-hexadecylamine and cetyltrimethylammoniurn salt etc. Several ions such as F-, Fe (CN)63- and Hg2+ interfere the determination. In order to avoid the interference, acetic acid (1 ml) was added to the -ample solution, and ODA was extracted with chloroform. After removing chloroform in vacuo, the residue was dissolved in 10 ml water, and ODA was determined by this method. The determination of ODA was not interfered by the presence of 500-fold of the ions. © 1980, The Japan Society for Analytical Chemistry. All rights reserved.