Cation selectivity of liquid-membrane electrodes based on macrocyclic lactones and lactonelactams

Carrier-Based Ion-Selective Electrodes and Bulk Optodes. 2. Ionophores for Potentiometric and Optical Sensors

“…A study of cyclic polyethers with lactam and lactone groups in the macrocyclic ring is interesting in view of the ionophore design. Whereas most lactams were found to give strong responses to divalent ions, lactones gave preferences for alkali metal ions and, in some cases, selectivities similar to those observed for common monocyclic crown ethers (typical log (SSM): ≈−1.7; 1,2-dichloroethane) …”

“…Whereas most lactams were found to give strong responses to divalent ions, lactones gave preferences for alkali metal ions and, in some cases, selectivities similar to those observed for common monocyclic crown ethers (typical log K K,Na pot (SSM): ≈-1.7; 1,2-dichloroethane). 347 Two ionophores with a thiolactone and two lactone groups were not distinguishable in this respect from the pure lactones but responses to transition metal ions were not determined. Exceptions to these common trends should, however, be interpreted with care as the slopes of the K + response were not reported.…”

“…While ISE membranes containing DNNS but no added sites are Cs + selective and give sub-Nernstian slopes, addition of 48 mol % cationic sites led to a moderate Ba 2+ selectivity and Nernstian responses (log (SSM): Na + , −1.4; K + , −1.1; Ba 2+ , +0.3; Sr 2+ , 0.0; oNPOE, TDDMACl). Some macrocyclic ionophores with several lactam or/and lactone groups gave moderate discrimination of many common cations . A reinvestigation with added ionic sites might reveal some interesting Ba 2+ ionophores.…”

“…The Sr 2+ complex of nonylphenoxypoly(ethyleneoxy)ethanol ( Ba 2+ -1 ) was used in an ISE with the aim of Sr 2+ determinations in a nuclear waste program, but the response to Ba 2+ was found to be larger than that to the primary ion . A higher discrimination of Ba 2+ was obtained with a macrocyclic triester diether compound ( Sr 2+ -1 , log (SSM): −1.6; 1,2-dichloroethane, cellophane film) but in this case Ca 2+ interfered more strongly (log −0.5) . The best characterized Sr 2+ ISE with a discrimination of both Ba 2+ and Ca 2+ seems to be an ISE with a diamide that was synthesized in the course of a study of Ba 2+ selective electrodes ( Sr 2+ -2 , log (SSM): Ba 2+ , −0.7; Ca 2+ , −1.4; other alkali and alkaline earth metal ions <−3.3; oNPOE, KTpClPB; selectivity estimated here from log as given in the original paper) .…”

“…594 A higher discrimination of Ba 2+ was obtained with a macrocyclic triester diether compound (Sr 2+ -1, log K Sr,Ba pot (SSM): -1.6; 1,2-dichloroethane, cellophane film) but in this case Ca 2+ interfered more strongly (log K Sr,Ca pot -0.5). 347 The best characterized Sr 2+ ISE with a discrimination of both Ba 2+ and Ca 2+ seems to be an ISE with a diamide that was synthesized in the course of a study of Ba 2+ selective electrodes (Sr 2+ -2, log K Sr,J pot (SSM): Ba 2+ , -0.7; Ca 2+ , -1.4; other alkali and alkaline earth metal ions <-3.3; oNPOE, KTpClPB; selectivity estimated here from log K Ba,J pot as given in the original paper). 595 A promising discrimination of Mg 2+ and Ca 2+ was also found for several rather hydrophilic benzo-18-crown-6 derivatives, suggesting that the Sr 2+ selectivity is markedly enhanced by the introduction of a side arm with two or more oxygens.…”