Lifetime of neutral-carrier-based liquid membranes in aqueous samples and blood and the lipophilicity of membrane components

Dinten, O.; Spichiger, Ursula E.; Chaniotakis, Nicolas.; Gehrig, Peter; Rusterholz, Bruno; Morf, Werner E.; Simon, W.

doi:10.1021/ac00006a009

Cited by 242 publications

(164 citation statements)

References 19 publications

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“…It is surprising that the formal complex formation constant of V with Ag + is about 300 times lower than that of VI since in a competition experiment with a 1:1 mixture of both ionophores and 0.5 equivalents of Ag + , the 1 H NMR spectrum indicated that V was complexed and VI was not [17]. However, in that experiment in the rather apolar solvent CDCl 3 , the counterion was CF 3 SO 3 − , whereas the sensor membrane investigated here is based on the polar o-NPOE (dielectric constant, 23.9 [48]) and the counterion is a substituted tetraphenylborate, TFPB − . A likely explanation of the observed difference is that the ion pairs with CF 3 SO 3 − in CDCl 3 are strong, whereas with TFPB − in o-NPOE they are weak [39].…”

Section: Resultsmentioning

confidence: 79%

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

Szigeti

Malon

Vigassy

et al. 2006

Analytica Chimica Acta

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Ten Ag + -selective ionophores have been characterized in terms of their potentiometric selectivities and complex formation constants in solvent polymeric membranes. The compounds with π-coordination show much weaker interactions than those with thioether or thiocarbamate groups as the coordinating sites. Long-term studies with the best ionophores show that the lower detection limit of the best Ag + sensors can be maintained in the subnanomolar range for at least one month. The best ionophores have also been characterized in fluorescent microspheres. The so far best lower detection limits of 3× 10 −11 M (potentiometrically) and 2 × 10 −11 M Ag + (optically) are found with bridged thiacalixarenes.

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Section: Resultsmentioning

confidence: 79%

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

Szigeti

Malon

Vigassy

et al. 2006

Analytica Chimica Acta

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“…The lipophilicity of each ionophore was determined based on a method reported by Dinten et al 22 The stationary phase was RP-C18-silica gel (Merck). The mobile phase was anethanolwater mixture in a volume ratio of 7:3.…”

Section: Lipophilicity Measurementsmentioning

confidence: 99%

“…If the two types of ligands are applied to measurements in physiological samples, they fulfil the theoretically required selectivity coefficients comparable to real conditions in mixed solutions. 25 On the other hand, the relatively low lipophilicity of K22B5 (log PTLC=3.94) does not meet the required lipophilicity of an ionophore for physiological measurements 22,26 (required lipophilicity of an ionophore in continuous measurements of blood serum (30 days, 24 h: log PTLC=8.4).…”

Section: +mentioning

confidence: 99%

“…Loss in the plasticizer is much less critical. 21,22,26 The required lipophilicities for membrane components to obtain sensors of a specified lifetime have been previously calculated. 22,26 For example, in continuous-flow use with a lifetime of over 30 days and 24 h per day, the required lipophilicity values log PTLC of ionophores are >2.3 and >8.4, for continuous measurements in urine and serum respectively.…”

Section: Comparison Of Lipophilicitiesmentioning

confidence: 99%

“…22,26 For example, in continuous-flow use with a lifetime of over 30 days and 24 h per day, the required lipophilicity values log PTLC of ionophores are >2.3 and >8.4, for continuous measurements in urine and serum respectively. 22,26 The lipophilicities, log PTLC, of the membrane components investigated here are shown in Fig. 7.…”

Section: Comparison Of Lipophilicitiesmentioning

confidence: 99%

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A Comparison of Neutral Mg2+-Selective Ionophores in Solvent Polymeric Membranes: Complex Stoichiometry and Lipophilicity

2000

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Mg 2+ -selective ionophores were intensively investigated in order to obtain Mg 2+ sensors sufficiently selective for the determinations of human specimens. From basic considerations discussed before, 1,2 electrically neutral lipophilic amide derivatives were considered to be attractive candidates for designing magnesium-selective ionophores and sensing layers. A set of amides were synthesized and investigated, whereof the di-and tripodal malondiamides showed attractive features. [3][4][5][6][7][8][9][10][11][12] The discrimination of calcium, potassium and sodium ions by these ionophores was of primary interest. For comparability of different ionophores and membranes, the procedures for determining the selectivity coefficients were standardized according to IUPAC. 2,13 Bis(malondiamides) were the first compounds which showed a pronounced preference of magnesium ions. [5][6][7] Membrane electrodes containing these ligands achieved selectivities in the range of log K pot Mg,Ca >-1.0 (SSM) in the presence of 120 mol% of lipophilic borate salt in solvent polymeric membranes.Tris(malondiamides) were expected to improve the discrimination of alkaline over alkaline earth ions, since Mg 2+ is typically involved in octahedral coordination and is supposed to form 1:1 complexes with a tripodal ligand. Using ionophores of this class, the electrodes selectively responded to Mg 2+ discriminating Ca 2+ by more than a factor of ten (SSM log K pot Mg,Ca <-1). Attaching three secondary malondiamide units to a benzene core e.g. in ETH 3832 (see Fig. 1), improved the selectivity for magnesium over calcium ions to a significant extent.9,10 The corresponding, more lipophilic adamantylamide derivative, ETH 5506, shows satisfying selectivity of Mg 2+ against Ca 2+ , K + and Na + (SSM, log K pot Mg,Ca =-1.8, log K pot Mg,K =-2.9 and log K pot Mg,Na = -4.1) for physiological applications. 2,11,12 Recently, malondiamide derivatives of diazacrown ethers were synthesized and studied by Suzuki et al. 14 Compared to ETH 5506, K22B5 shows even higher Mg 2+ selectivity against Ca 2+ (SSM, log K pot Mg,Ca =-2.5), but poor discrimination of monovalent cations (SSM, log K pot Mg,K =-1.5 and log K pot Mg,Na =-3.2). The addition of lipophilic borate salt (e.g. tetraphenylborate salt) to the neutral carrier-based membranes provides lipophilic anionic sites in the polymeric electrode membranes, which support the selective extraction of Mg 2+ , and have been shown also to be favourable in other aspects. 2,15,16 The concentration of anionic sites affects the selectivity of an electrode, primarily by controlling the concentrations of both the exchangeable cations, and the free ionophore available for complexation at the membrane/solution interface. The optimum composition of a Mg 2+ -selective membrane with respect to the borate/ligand ratio is estimated by taking the charge number of interfering ions and the theoretical stoichiometry of ion-ligand complex into account. 16 Referring to the theoretical treatment of the optimum ratio of borate to ligand,...

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Development of Magnesium-Ion-Selective Microelectrodes Based on a New Neutral Carrier ETHT 5504

Zhang

Fakler

Spichiger³

1998

Electroanalysis

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Two types of magnesium-selective microelectrodes based on a new synthetic neutral carrier ETH T 5504 are presented. One type of microelectrode is applicable to the determination of intracellular free Mg 2þ molality without interference from alkaline or alkaline-earth metal ions versus a typical intracellular ion background of 10 mmol/L NaCl, 100 mmol/L KCl, and 1 mM CaCl 2 . The response function showed a slope of 28.6 Ϯ 0.4 mV (1 SD per decade), and a detection limit at 10 ¹5.1 Ϯ 0.1 mol/L. A magnesium-selective electrode with different composition of the membrane cocktail has been employed for assays of both intracellular and extracellular Mg 2þ -activities, with improved discrimination of Ca 2þ and other physiological cations compared to electrodes based on ETH 1117, ETH 5214 and ETH 7025, respectively. This is the first report where Mg 2þ -selective microelectrodes can be applied to extracellular Mg 2þ -measurements. The microelectrodes based on ETH T 5504 perfectly discriminate the physiological extracellular ion background. Electrodes with tip diameters of typically 1 mm have an average electrical resistance of 3.0 × 10 10 Q, and a response time, t 90 % , of 3 s. The lifetime of the microelectrodes is longer than 1 week and the emf-drift after 1day conditioning period is Յ0.3 mV/ h. An example of measurements of the Mg 2þ -molality in low volumes of specimen is described in this article for blood serum of rats.

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Lifetime of neutral-carrier-based liquid membranes in aqueous samples and blood and the lipophilicity of membrane components

Cited by 242 publications

References 19 publications

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

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

A Comparison of Neutral Mg2+-Selective Ionophores in Solvent Polymeric Membranes: Complex Stoichiometry and Lipophilicity

Development of Magnesium-Ion-Selective Microelectrodes Based on a New Neutral Carrier ETHT 5504

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