O-Nitrophenyloctyl ether

Some ISEs containing no inner reference solution, as well as tubular potentiometric sensors, has been used in conjunction with FI systems for the determination of vitamins B, and Bg in pharmaceutical preparations. The membranes used for this purpose were prepared from the vitamin tetra(2-chlorophenyl)borate dissolved in o-nitrophenyloctyl ether and immobilized in PVC. The intrinsic behaviour of the tubular electrodes was assessed by using a low-dispersion single-channel FI manifold and compared with those of conventionally-shaped electrodes using the same membrane the results provided by both were very similar [119]. 

Other components of the design [138—142] include the choice of the crown size or even the use of open-chain metalloclefts, not necessarily polyether armed. The issue of special importance for extraction and transport applications is the selection of substituents ensuring a necessary lipo-philicity-solubility balance. For example, use of a cyclohexano moiety as shown above, instead of the more common o-phenylene bridge between nitrogens, enhances solubility in the membrane phase. The modification of the polyether chain with binaphthyl or calixarene substituents provides high membrane transport rates due to increased ionophore lipophilicity [138,142]. Some representative examples (initial fluxes, in 10 mol cm h , through o-nitrophenyloctyl ether-impregnated Accurel membrane 1 M source urea [138]) are as follows. 

At present, the most commonly used solvents are NB and DCE. Other solvents which have been considered include, for example, propiophenone (39), 4-isopropyl-1-methy 1-2-nitrobenzene (40), dichloromethane (41), o-nitrophenyloctyl ether (42). In order to have more flexible choices, organic solvent mixtures have also been employed for example, NB with chlorobenzene (43), benzonitrile, benzene (44), and tetrachloromethane (45). 

TABLE 8.5 The Standard Molar Gibbs Energy for Transfer, A G (I)/kJ moH, of Univalent Ions Between Mutually Saturated Water and o-nitrophenyloctyl Ether and Water and 1,2-dichloroethane at 25°C, Obtained from Exchange Equilibria [49]... 

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