1997 Volume 13 Issue 3 Pages 437-446
Potentiometric behaviors of bilayer lipid membranes (BLMs) incorporated with such ionophores as valinomycin, crown ethers and acyclic polyethers were described for various alkali and alkaline earth metal ions. The ionophores were directly incorporated into planar BLMs formed by the folding method. Among seven kinds of ionophores examined, only the valinomycin- and ETH 4120-based BLMs generated potentiometric Nernstian responses. However, simultaneous incorporation of anionic sites, such as sodium tetrakis[3, 5-bis(trifluoromethyl)phenyl]borate (NaTFPB) or potassium tetrakis(4-chlorophenyl)borate (KTpClPB), was found generally effective for inducing potentiometric Nernstian responses of the ionophore-based BLMs. The added anionic sites were also found to decrease the membrane resistance, leading to improvement of probability of potential measurements, and to lower the detection limits by maintaining Nernstian slopes, thereby providing a basis for quantitative BLM sensors. By comparing the potentiometric responses of ionophore-incorporated BLMs with and without added anionic sites, the role and significance of the anionic sites in potentiometric response of BLMs based on ionophores was discussed.
