Selective determinations of amines and quaternary ammonium compounds as ion pairs with methyl orange by an automated method applicable to single dose analysis

Abstract

Abstract Aliphatic amines and quaternary ammonium compounds can be determined photometrically after extraction as ion pairs with methyl orange. Extraction conditions are calculated from constants for the extraction procedure and side-reactions. Methods for the selective determination of ammonium ions of different degrees of substitution are given. Quaternary ammonium ions are isolated by extraction at pH 12. The amines are extracted as ion pairs at pH 4.6 and selective determinations can be made after primary and secondary amines are masked by acetylation and primary amines by coupling with salicylic aldehyde. An automated application of the method on a Technicon AutoAnalyzer is presented. A complete analysis of a sample containing the four kinds of ammonium ions requires four separate runnings. The same basic manifold is used for all the runnings with some rearrangements for the masking procedures. The method has been tested on benzhexol, diethylpropion, dodecylamine, emepronium, N-hydroxyethylpromethazine, promethazine and protriptyline. Recoveries of about 100% with a relative variation of 1–2% were obtained.