Determination of quaternary ammonium ion as the precipitate with tetrathiocyanatocobaltate(II) by densitometry

Abstract

A simple and rapid method for the determination of quaternary ammonium ions (Q+) has been developed. The method is based on the formation of the blue precipitate of Q₂[Co(SCN)₄] by treating Q⁺ with cobalt(II) and thiocyanate, collection of the precipitate on a membrane filter and measurement of the reflecting absorbance of the resulting thin layer of precipitate. Zephiramine, cetyltrimethylammonium, tetradecyl-trimethylammonium, dodecyltrimethylammonium, tetrapentylammonium and tetrabutylammonium ions can also be determined. In addition a non-ionic surfactant, Triton X-100, can be determined in the presence of strontium chloride.