Potentiometric detection of amines in ion chromatography using macrocycle-based liquid membrane electrodes

Potentiometric detection employing solid-state electrodes was applied to th e determination of organic amines in cation-exchange, and in ion-interactio n chromatography. The amines included nine industrial alkylamines, the biog enic amines putrescine and cadaverine, the neurotransmitter acetylcholine a nd choline. Three PVC-based liquid membrane electrode coatings were used, i ncorporating respectively the lipophilic cation-exchanger tetrakis(p-chloro phenyl)borate, a combination of tetrakis(p-chlorophenyl)borate and dibenzo- 18-crown-6, or a combination of tetrakis(p-chlorophenyl)borate and a calix[ 6]arene. The three solid-state electrodes allowed sensitive detection of al l amines. The addition of macrocycles with molecular recognition properties resulted in a superior sensitivity when compared to the tetrakis(p-chlorop henyl)borate-based electrode. The effect was most significant for the small er amines which form the most stable complexes with the macrocycles. Detect ion limits of the order of 10(-6) M (injected concentration) were measured for mono- and diamines for the macrocycle-based electrodes. (C) 2001 Elsevi er Science B.V. All rights reserved.