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The electrochemical behavior of three differently charged drug molecules (zwitter-ionic acetylcarnitine, bi-cationic succinylcholine and tri-cationic gallamine) was studied at the interface between two immiscible electrolyte solutions. Tetramethylammonium was used as a model mono cationic molecule and internal reference. The charge and molecular structure were found to play an important role in the drug lipophilicity. The studied drugs gave a linear correlation between the water – octanol (log P octanol ) partition coefficients and the electrochemically measured water – 1,2-dichloroethane (log P DCE ) partition coefficients. Comparison with tetraalkylammonium cations indicating that the correlation between log P octanol and log P DCE is molecular structure dependent. The highest measured sensitivity and lowest limit of detection were found to be 0.543 mA·dm 3 ·mol − 1 and 6.25 μM, respectively, for the tri-cationic gallamine. The sensitivity for all studied ions was found to be a linear function of molecular charge. The dissociation constant of the carboxylic group of zwiter-ionic acetylcarnitine was calculated based on voltammetric parameters and was found to be 4.3. This study demonstrates that electrochemistry at the liquid – liquid interface is powerful technique when it comes to electroanalytical or pharmacokinetic drug assessment. [ABSTRACT FROM AUTHOR]

Abstract: A new and divergent synthetic route to oligodiacetylene (ODA) building blocks has been developed via Sonogashira reactions under a reductive atmosphere. These central building blocks provide a new way for rapid preparation of long ODAs. In addition, we report on their optoelectronic properties which are dependent on their end cap. Finally, the formation of their radical cations, and their optical properties and reactivity towards nucleophiles are investigated. [Copyright &y& Elsevier]

We investigated in detail the permeation selectivity in the electro-dialysis of Na+, K+, Mg2+ and Ca2+ in both binary and quaternary mixtures using a supported liquid membrane (SLM). The SLM consisted of the organic liquid 2-nitrophenyl octyl ether (NPOE) containing a lipophilic anion, i.e. tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, as the cation-exchanging site, which was used to fill the pores of the supporting membrane AccurelR. We first determined the electro-phoretic mobilities of the migrating cations in single salt solutions, yielding: Na+ > K+ > Mg2+ > Ca2+. This order reflects the different size of the migrating cations. The monovalent cations Na+ and K+ migrate in the dehydrated state and the divalent cations Ca2+ and Mg2+ migrate in a (partly) hydrated state, a conclusion was supported by Karl Fisher titrations. Both binary and quaternary salt experiments showed a permeation selectivity in the following order: K+ > Na+ > Ca2+ > Mg2+. Since this order does not correlate with the order of electro-phoretic mobilities, we have determined the ion-exchange selectivity constant (K ex) and found: K+ > Ca2+ > Mg2+ ≈ Na+. We conclude that the overall permeation selectivity is determined by the combination of ion-exchange selectivity and electro-phoretic mobility of the cations present in the membrane. • First-time, monovalent/divalent ion-selective electro-dialysis with a supported liquid membrane (SLM) • Ion permeation selectivity: K+ > Na+ > Ca2+ > Mg2+ • Electrophoretic mobility: dehydrated ions (Na+ > K+) > partly hydrated ions (Mg2+ > Ca2+ ions) • Ion-exchange selectivity constant between water and membrane: K+ > Ca2+ > Mg2+ ≈ Na+ • Observed permeation selectivities determined by balance of ion-exchange selectivity and electrophoretic mobilities. [ABSTRACT FROM AUTHOR]

This study demonstrates the effective separation of alkali metal cations using a Supported Liquid Membrane (SLM) containing lipophilic, negatively charged borate moieties, operating under electro dialysis conditions. The selectivity of the membrane is essentially based on differences in dehydration energy and mobility between ion species. The system favors the ion species with the largest crystal radius, despite its lower mobility. In mixtures of K+ and Na+, the SLM separates K+ from Na+ with a separation efficiency ranging from ~20% to 90%, depending on the feed solution composition. With solutions containing either K+ or Na+ and Li+, the K+/Na+ over Li+ separation efficiency is nearly 100%. Addition of 15-crown-5 derivative does not improve SLM behavior, but slows down the K+ current by approximately 30% whereas the Na+ current remains unaffected. As supported by simulations, the free K+ and Na+ ratio in the membrane (and with that the current ratio) is entirely defined by partitioning and the feed concentration ratio, regardless the presence of 15-crown-5. As a result, the current ratio of two ion species can be described exclusively in terms of their feed concentrations and crystal radii because the latter parameter defines both partitioning and mobility. Unlabelled Image • Alkali metal cations are effectively separated by a Supported Liquid Membrane (SLM) under electro dialysis condition. • Membrane selectivity ranges from ~10 (K+ over Na+) to ~850 (Na+/K+ over Li+) at equal feed concentration. • Obtained membrane selectivity indicates an increasing permeation rate with increasing crystal radius of the cation. [ABSTRACT FROM AUTHOR]