Guanidinium ion-selective electrodes based on dibenzo-27-crown-9 and tetraphenylborate

Abstract

PVC membrane ion-selective electrodes based on dibenzo-27-crown-9 (DB27C9) and guanidinium tetraphenylborate (GuTPB) are described. Of six solvent mediators tested for DB27C9 based electrodes, dibutyl phthalate (DBP) gave the best fast response with near-Nernstian characteristics, followed by dioctyl adipate and dioctyl sebacate. 2-Nitrophenyl octyl ether, 2-nitrophenyl phenyl ether and dioctylphenyl phosphonate were unsatisfactory. The effect of GuTPB in electrode membranes with DBP as solvent mediator was studied. Addition to DB27C9 membranes produced less sensitive electrodes compared with those based on the crown ether alone, but the selectivity (separate solution method) towards guanidinium over some metal ions was improved. Electrodes based on GuTPB alone using DBP as a solvent mediator gave good responses and good selectivity towards guanidinium over metal ions but when dioctylphenyl phosphonate was used as the solvent mediator, the electrodes showed good all-round selectivity towards guanidlnium ions. However, tetraphenylborate based electrodes were more sluggish in response.