Polymer Membrane Ion-Selective Electrodes-What are the Limits?

Abstract

This article reviews recent advances in the ®eld of potentiometric solvent polymeric membrane electrodes. These sensors have found widespread applications in a variety of ®elds, especially in the area of clinical diagnostics. Emphasis is given on the discussion of the theoretical and practical limits of ionophore-based ion-selective electrodes, with a special focus on electrode sensitivities, characterization of selectivities and dramatic improvements in detection limits. Advances in ionophore design and in the underlying model assumptions are also discussed. It is shown that a multitude of exciting new research possibilities have recently emerged in this well±established ®eld.

Novel potentiometric and optical silver ion-selective sensors with subnanomolar detection limits

“…Alternatively, the segmented sandwich technique was used according to reference [39]. The conditioning, measuring, and internal solutions were 10 −3 M AgNO 3 . Because of using a polar plasticizer (o-NPOE), no formation of ion pairs in the membrane was considered (β IL n was calculated according to equation 10 in [39]).…”

“…Since the description of the first Ag + -selective ionophore in 1986 [1], at least 50 different lipophilic ligands have been applied in Ag + -selective membranes (earlier contributions are covered in [2,3]; for a selection of more recent papers, see [4][5][6][7][8][9][10][11][12][13][14][15][16]{Johnson, 2002 #21}{Kim, 2005 #56}{Zhang, 2006 #55}). In spite of this large number of compounds, there is an ongoing interest in developing highly selective lipophilic complexing agents for Ag + [13][14][15][17][18][19].…”

Real-Time Electrochemical Monitoring: Toward Green Analytical Chemistry

“…4 The integration of electrochemical biosensors with the remotely deployed probes adds new dimensions of specificity into in situ monitoring of pollutants. 5 In the adaptation of enzyme electrodes to a submersible operation, one must consider the influence of actual field conditions (pH, salinity, temperature) upon the biocatalytic activity. The lack of long-term enzymatic stability can also limit the prolonged operation of such biocatalytic probes.…”

“…4 Similarly, recent developments in polymer membrane ion-selective electrodes have "pushed" the detection limits of these potentiometric devices to a similar level. 5 The coupling of modern electrochemical detection principles with recent advances in microelectronics and microfabrication has led to powerful and compact analytical devices for real-time, in process-monitoring. These developments have led to a substantial increase in the popularity of electroanalysis, and to its expansion into new phases and environments.…”

Influence of Incorporated Lipophilic Particles on Ion Fluxes Through Polymeric Ion‐Selective Membranes

“…In recent years, it has been well documented that these biasing effects can be largely reduced by an appropriate choice of the inner solution and membrane composition [8,13,14] or by applying an external current [15 ± 17]. By such means, lower detection limits in the range of 10 À7 À 10 À12 M have been reached for Pb 2 [8,16,18], Ca 2 [14,19,20], K [21], NH 4 [21], Cd 2 [22], and Ag [23]. At the same time, a much better selectivity behavior has been achieved in all these cases.…”