Cationic complexes of nonylphenoxypoly(ethyleneoxy)ethanol: Extraction into dichloromethane and ion-selective electrode properties

Abstract

Tetraphenylborate (TPB) salts of calcium, strontium and barium complexes of nonylphenoxypoly(ethyleneoxy)ethanol (NP) have been prepared from the commercially available Antarox range of NPs and screened for their suitability as ion-selective electrode sensors. For selectivity and general ion-selective electrode response behaviour, the best systems are those involving the barium complexes for barium ion response. TPB salts of calcium and barium complexes of dicyclohexyl-18-crown-6 have also been prepared. The complexing tendency of NPs, dicyclohexyl-18-crown-6 and Antarox with alkali metal and alkaline earth metal cations is described in terms of partitioning the picrates of the metal ion complexes from aqueous chloride solutions between water and dichloromethane. As well as percentage picrate extraction, the “bulk extraction constants” show the affinity of dicyclohexyl-18-crown-6 for alkali metal and alkaline earth cations to vary in the order K > Rb > Cs > Na > Li and Ba > Sr > Be > Ca > Mg, respectively, with the position of beryllium being anomalous and possibly related to the extraction of beryllium into the organic layer even in the absence of coordinating polyether or NP. For the Antarox NPs, the sequences are Rb > K > Cs > Na > Li and Be ⪢ Ba > Sr > C a > Mg, respectively.