Liquid crystalline mesophases of pluronics (L64, P65, and P123) and transition metal nitrate salts ([M(H2O)6](NO3)2)

The triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymers, Pluronics (L64, P65, and P123), form liquid crystalline (LC) mesophases with transition metal nitrate salts (TMS), [M(H(2)O)(n)](NO(3))(2), in the presence and absence of free water in the media. In this assembly process, M-OH(2) plays an important role as observed in a TMS:C(n)EO(m) (C(n)EO(m) is oligo(ethylene oxide) nonionic surfactants) system. The structure of the LC mesophases and interactions of the metal ion-nitrate ion and metal ion-Pluronic were investigated using microscopy (POM), diffraction (XRD), and spectroscopy (FTIR and micro-Raman) techniques. The TMS:L64 system requires a shear force for mesophase ordering to be observed using X-ray diffraction. However, TMS:P65 and TMS:P123 form well structured LC mesophases. Depending on the salt/Pluronic mole ratio, hexagonal LC mesophases are observed in the TMS:P65 systems and cubic and tetragonal LC mesophases in the TMS:P123 systems. The LC mesophase in the water/salt/Pluronic system is sensitive to the concentration of free (H(2)O) and coordinated water (M-OH(2)) molecules and demonstrates structural changes. As the free water is evaporated from the H(2)O:TMS:Pluronic LC mesophase (ternary mixture), the nitrate ion remains free in the media. However, complete evaporation of the free water molecules enforces the coordination of the nitrate ion to the metal ion in all TMS:Pluronic systems.     

Synthesis of arylated anthraquinones by site-selective Suzuki–Miyaura reactions of the bis(triflates) of 1,3-di(hydroxy)anthraquinones

Arylated anthraquinones were prepared by Suzuki–Miyaura reactions of the bis(triflates) of various 1,3-(dihydroxy)anthraquinones. While the reactions of the bis(triflates) of parent 1,3-(dihydroxy)anthraquinone and of 2-chloro-1,3-di(hydroxy)anthraquinone proceeded with very good site-selectivity, the corresponding reactions of the bis(triflate) of 2-fluoro-1,3-diarylanthraquinones were not site-selective, which was explained based on the π-donating effect of the fluorine atom.     

Flow injection spectrofluorimetric determination of iron(III) in water using salicylic acid

A simple and fast flow injection fluorescence quenching method for the determination of iron in water has been developed. Fluorimetric determination is based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The carrier solution used was 2 × 10⁻⁶ mol L⁻¹ salicylic acid in 0.1 mol L⁻¹ NH₄⁺/NH₃ buffer solution at pH 8.5. Linear calibration was obtained for 5–100 μg L⁻¹ iron(III) and the relative standard deviation was 1.25 % (n = 5) for a 20 μL injection volume iron(III). The limit of detection was 0.3 μg L⁻¹ and the sampling rate was 60 h⁻¹. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully applied to the determination of low levels of iron in real samples (river, sea, and spring waters).     

Flow-injection potentiometric applications of solid state Li+ selective electrode in biological and pharmaceutical samples

A solid state polyvinyl chloride (PVC) membrane Li⁺-selective electrode was prepared and used as a detector in a low-dead volume flow through cell for the determination of Li⁺ in pharmaceutical formulations and human serum samples. The potentiometric performance characteristics of the electrode were calculated under the optimized flow conditions. The electrode had near-Nernstian behavior in the concentration range of 0.1–100 mM (R ² = 0.9981) with a slope of 61.34 mV decade⁻¹ and detection limit of 0.080 mM. The relative standard deviation of the electrode response for eight replicate measurements of 100, 10, and 1 mM Li⁺ was 0.43%, 0.45%, and 0.99%, respectively. The designed flow-through cell detector system revealed sampling rates of approximately 70 injections per hour. Flow injection potentiometry (FIP) results obtained for the pharmaceutical formulations were in good harmony with the atomic emission spectrophotometry results. However, the electrode could not be used successfully for the direct analysis of real serum samples in FIP.