Electrodes based on PVC matrix membranes containing one of six crown ethers with 2-nitrophenyl octyl ether or dibutyl phthalate solvent mediator have been studied for their potentiometric response to 4,4′-dipyridyl (DPy), diquat (DQT) and paraquat (PQT) dications. The data are discussed in terms of quality of potentiometric response related to conformational phenomena of crown ethers in their complexation with these dications.
Good ion-selective electrode properties were characteristic of the 4,4′-DPy systems based on bis(metaphenylene-32-crown-10)(BMP32C10), bis(metaphenylene-38-crown-12)(BMP38C12), bis(paraphenylene-34-crown-10)(BPP34C10), bis(paraphenylene-37-crown-11)(BPP37C11) and dinaphthalene-36-crown-10 (DN36C10). The calibration slope was between 33 and 41 mV decade–1, extending down to 1.7–6 µM. Interferences from potassium, ammonium, guanidinium, barium, DQT and PQT ions were low except for the BPP34C10 electrode where DQT caused some interference. A sixth electrode, based on dibenzo-30-crown-10 (DB30C10), showed similar calibration behaviour towards 4,4′-DPy but was much less selective.
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