Potassium ion selectivity

Z. Gao, X. Zhou, G. Wang, P. Li, and Z. Zhao, Potassium ion-selective electrode based on a cobalt(II) -hexacyanoferrate film-modified electrode. Anal. Chim. Acta 244, 39-48 (1991). 

V. Krishnan, A.L. Xidis, and V.D. Neff, Prussian blue solid-state films and membranes as potassium ion-selective electrodes. Anal. Chim. Acta 239, 7-12 (1990). 

Potassium also can be measured by ICP/AES. The wavelengths at which it can be analyzed without interference from other metals are 766.49 and 769.90 nm. Other wavelengths may be used. Potassium ion in aqueous solution can be identified quantitatively by using a potassium ion-selective electrode attached to a pH meter having an expanded millivolt scale or to a specific ion meter having a direct readout concentration scale for potassium. 

A potassium-ion-selective, dendritic, fluorescing chemosensor, bearing three crown ether moieties in the periphery, shows a linear increase in fluorescence intensity with increasing potassium concentration (in acetonitrile). An important criterion for potassium chemosensors is their mode of action (selectivity) in the presence of large amounts of sodium. The tris-crown ether sensor shown in Fig. 8.16 is able to detect very small traces of potassium ions, even if large quantities of sodium ions are present in the same solution - such as in body fluids [55]. 

Schiff base 69 and sulfur-linked 70 ferrocene bjs-crown ether ligands have also been prepared and both were shown to be potassium ion selective, especially the S-linked macrocycle 70 [89]. Compound 69 did not behave well electrochemically and somewhat unexpectedly addition of to 70 resulted in a cathodic shift of the ferrocene redox couple, possibly due to conformational steric effects involving the electron lone pairs on sulfur, but certainly reminiscent of Sato s thia-ferrocenophanes discussed earlier. 

Standardization of sodium and potassium ion selective electrode systems to the flame photometric reference method Approved Standard, edition. NCCLS Document C29-A2, Wayne, PA NCCLS, 2000. 

National Committee for Clinical Laboratory Standards Standardization of Sodium and Potassium Ion-Selective Electrode Systems to the Flame Photometric Reference Method Approved Standard C29-AZ. Wayne, PA National Committee for Clinical Laboratory Standards, 1995,... 

Calix[4]tube a tubular receptor with remarkable potassium ion selectivity, P. Schmitt, P. D. Beer, M. G. B. Drew and P. D. Sheen, Angew. Chem. Int. Ed. Engl., 1997, 36, 1840. 

To date, the capability of macromolecular peptides as molecular recognition sites has been poorly characterized. Due to the analytical techniques available, first investigations on host-guest complexes were done in the homogeneous phase [55]. One of the most popular cyclic compounds is the depsipeptide, valinomycin, which can complex potassium ions selectively and carry them through lipid membranes [56], Another interesting receptor is the peptide antibiotic, vancomycin [57], This consists of a complicated tricyclic pep-tidic structure and can be used as chiral selector [58] in capillary electrophoresis and HPLC. 

A potassium ion-selective electrode is used to measure the concentration of potassium ion in a solution that contains 6.0 X 10 M cesium (activity). From Table 13.3, the electrode responds equally to either ion (i KCs = ) If the potential versus a reference electrode is —18.3 mV for a 5.0 X 10 M KCl solution and +20.9 mV in the sample solution, what is the activity of K in the sample Assume Nemstian response. 

A valinomycin-based potassium ion-selective electrode is evaluated for sodium interference using the fixed interference method. A potassium calibration curve is prepared in the presence of 140 mM sodium. The straight line obtained from extrapolation of the linear portion deviates from the experimental curve by 17.4 mV at a potassium concentration corresponding to 1.5 X 10 M. If the linear slope is 57.8 mV per decade, what is ATnok for the electrode ... 

Schiff base 69 and sulfur-linked 70 ferrocene bjs-crown ether ligands have also been prepared and both were shown to be potassium ion selective, especially the... 

Certain food and drug regulations regard all slow-release preparations as drugs and require their safety to be established prior to clinical application. Thus, a potassium ion-selective electrode has been employed to follow [416] the release parameters of 12 encapsulated potassium chloride tablets. Several of the tablets showed only medium dissolution rates for potassium and are unlikely to cause adverse effects such as gut ulceration. A sodium electrode has been similarly used to study the release of sodium phenobarbitone through a dialysis membrane into tris buffer [417]. Sodium in organic compounds has also been determined with an Orion 94-11 sodium electrode following combustion in a closed flask [418]. 

Mousavi, Z., Bobacka,J., Lewenstam,A, and Ivaska,A. (2009]. Roly(3,4-ethylenediox5ithiophene] (REDOT] doped with carbon nanotubes as ion-to-electron transducer in polymer membrane-based potassium ion-selective electrodes,/. Electroanal. Chem., 633, pp. 246-252. 

Figure 15-6b shows how the electrode works. The key in this example is the ligand, L (called an ionopkore), which is soluble inside the membrane and selectively binds analyte ion. In a potassium ion-selective electrode, for example, L could be valinomycin, a natural antibiotic secreted by certain microorganisms to carry ion across cell membranes. The ligand L is chosen to have a high affinity for analyte cation and low affinity for other ions. 

Apart from Pungor and co-workers (107), others have prospected in the area of bis crown ethers, e.g., Shono and co-workers have shown good potassium ion- selectivity for some bis (15-crown-5) derivatives (11M-115) where one containing a dodecyl group in the link exhibits good lipophilicity and longer lifetime for the resulting ISEs (115). 

To illustrate which components are necessary to prepare an ISE membrane, let us again go back to a simple extraction experiment as it was similarly described in Section 3.1.1. Consider an aqueous potassium chloride solution equilibrated with an immiscible organic phase containing an electrically neutral ionophore for K+, that is, a receptor compound that binds the potassium ion selectively. How does the phase boundary potential between these two phases depend on the KCl concentration in the aqueous phase Upon equilibration of the two phases, some KCl will be present in the organic phase (Figure 5). For low amounts of KCl in the system, the potassium ions in the organic phase will be present in the form of ionophore complexes, and there will be an excess of free ionophore, L. In comparison to the concentration of the ionophore complex, the organic phase concentration [K+] of free potassium ions that are not bound by the ionophore is very low and can be calculated from the formation constant, of the potassium ion complex, [LK+] ... 

Cellular metal ion transport is biologically important because our muscular and nervous systems are regulated by charged species. Cells use membrane channels to extract potassium ions selectively from environments containing both K+ and Na+. Because the K+ ion is /argerthan the Na+ ion, this process cannot be accomplished by simply restricting the channel diameter. Dr. Roderick MacKinnon showed that potassium selectivity arises from a preferential interaction between the potassium cation and the atoms of the protein amino acids composing the channel walls. 

Potassium ion-selective electrodes have great value for physiological studies. The selectivity of a liquid... 

After the diseovery of crown ethers, Lehn et al. synthesized cryptands, whieh eontain a double-cyclic crown ether structure (see Figure 1.3). Owing to the double-cyclic structure, cryptands can capture potassium ions selectively and strongly. This complexation behavior has received a great deal of attention because this system is very similar to the encapsulation of potassium ions by the antibacterial agent valinomycin. 

Ping, J., Y. Wang, J. Wu, and Y. Ying. 2011. Development of an all-solid-state potassium ion-selective electrode using graphene as the solid-contact transducer. Electrochem. Common. 13 1529-1532. 

Tarcah, J., Nagy, G., Toth, K., Pungor, E., Juhasz, G., KukoreUi, T., In vivo measurements with a potassium ion-selective microelectrode based on a new bis(crown ether). Anal Ghim Acta 1985, 178(2), 231-237. 

Nitrate and potassium ion-selective electrodes have been evaluated for use in moistened soils as opposed to soil extracts. " Soluble nitrate and K content of moist soil samples could be determined in the laboratory (r = 0.56-0.94) if several limitations such as inconsistent crmtact between soil and electrode and... 

Kim HJ, Hummel JW, Birrell SJ (2006) Evaluation of nitrate and potassium ion-selective membranes for soil macronutrient sensing. Trans ASABE 49(3) 597-606... 

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