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Electrospray ionization (ESI) is a versatile and effective ionization technique of liquid samples for various mass spectrometric (MS) measurements. Therefore, ESI is widely used as an interface in MS detection for CE, 1 HPLC 2 and combinatorial separation systems. 3 The advantages of ESI/MS in solution chemistry research are also recognized because of its high potential in the structural identification or chemical speciation of compounds formed in diluted solutions. 4 In some cases, the chemical equilibria and kinetics of complexation in a solution as well as in a gas phase could be studied by ESI/MS. 5 However, the solvents usable in ESI/MS are usually limited to polar or protic solvents, such as methanol, ethanol, acetonitrile, dimethylsulfoxide and water. Therefore, non-polar organic solvents, which can solubilize highly hydrophobic compounds, are difficult to be used in an ordinal ESI/MS. For example, heptane and toluene, which are used very often in the solvent extraction of trace amounts of metal ions or organic compounds in environmental samples, can not be introduced directly to ESI, because of their very low conductivities.6 If these kinds of inert solvents could be used in ESI/MS, the variety of samples in ESI/MS must be significantly extended.The present study reports a method to introduce an inert organic phase into ESI/MS by producing organic droplets in a flowing aqueous phase at the point just prior to ionization. This method is applicable for ESI/MS measurements of very small amounts of hydrophobic compounds that can be dissolved or extracted into an inert organic solvent. As an example, a hydrophobic extractant, 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP, or HL), in toluene was employed. The distribution constant (log KD) of 5-Br-PADAP, obtained as 4.78 in toluene/water, proved its high hydrophobicity. Furthermore, the solvent extraction of Cu(II) with 5-Br-PADAP in toluene was attempted in a two-phase flow system. Figure 1 shows a schematic drawing of the electrospray ionization interface of the micro-flow liquid-liquid extraction system. The interface is composed of an outer stainless-steel capillary (0.4 mm o.d., 0.2 mm i.d.) and an inner silica capillary (0.158 mm o.d., 0.050 mm i.d.). The tip of the silica capillary was made as fine as 13 µm o.d. and 7 µm i.d. by pulling it under heating with a CO2 laser (SYNRAD, 10.5 µm wavelength, 12.0 W, 3 mm beam waist). The end of the silica capillary tip was positioned about 1 mm inside from the end of the outer stainless-steel capillary. A water-saturated toluene phase containing 1.0 × 10 -3 M 5-Br-PADAP was pumped in the inner silica capillary at a flow rate of 0.001 -0.02 ml/h. Into the outer stainless-steel capillary, 5.0 × 10 -6 M Cu(II) in the aqueous 0.0010 M acetic acid was introduced from a PTFE tee connector at a flow rate of 0.1 ml/h as an outer aqueous phase. For pumping both phases, two syringe pumps (Harverd 11) were used. A high voltage of 2 -5 kV was applied by a power supply (Glassman) to the stainless-steel for generat...

EXAFS (Extended X-ray Absorption Fine Structure) experiments on various polynuclear molybdate and tungstate compounds revealed the unusual phenomenon that Mo–O peaks which should appear at around 1.9 Å in Fourier transforms of the EXAFS spectra for Mo6O192− and PMo12O403− are hardly discernible, while the tungstates and other molybdates give the metal–oxygen peaks normally. It is concluded that the Debye–Waller factors for the metal-bridging oxygen bonds in Mo6O192− and PMo12O403− are exceptionally large (≥0.08 Å). The shape of the Raman bands for the Mo6O192− pertaining to the vibration involving the bridging oxygens supports the large σ values estimated. EXAFS measurements were also performed for AsMo12O403−, SiMo12O404−, and PMo12O403−. The compounds with large Debye–Waller factors seem to be unstable against reductants.

ABSTRACT:Optically active polyamides having ( -)-1,2-trans-diaminocyclohexane [( -)-DA] or ( + )-1,2-trans-cyclohexane dicarboxylic acid [( + )-CDA] residue in main chain were synthesized by polycondensation. Polyamides with a p-phenylene group in main chain showed better resolution for several racemic compounds than the polyamides with a polymethylene group [ fCH 2:);; (n=2-7)] in main chain. Among the polyamides with a polymethylene group in main chain, the polyamides with a shorter polymethylene group showed better chiral recognition abilities than the polyamides with a longer polymethylene group. Polyamides derived from ( -)-trans-3,6-endomethylene-1,2,3,6-tetrahydrophtharic acid [( -)-ETHF] showed low chiral recognition ability. CD spectra of these polyamides showed characteristic patterns. Odd-even effect was observed in CD spectra of the polyamides having a series of a polymethylene group.

The electrophoretic behaviors of five bases and corresponding nucleosides in the oil in water (o/w) microemulsion capillary electrophoresis, microemulsion electrokinetic chromatography (MEEKC), were examined in comparison with those in normal capillary zone electrophoresis (CZE). The microemulsion systems were composed of heptane, sodium dodecyl sulfate (SDS), 1-butanol and 10 mM phosphate buffer (pH 7.0) or toluene, SDS, 1-butanol and 5 mM carbonate buffer (pH 10.0). CZE was carried out in the range of pH 9.7-10.9, and the dissociation constants, pKa, of the bases and nucleosides and the electrophoretic mobilities of the anionic forms were determined. The electrophoretic behaviors of the solutes in the microemulsion systems were analyzed from their pKa, the electrophoretic mobilities of the anions determined by CZE, and the distribution constants, K(D), of the neutral forms between the microemulsion droplets and the outer aqueous phase. The importance of adsorption mechanism in MEEKC system was suggested from the correlation between log K(D) and log P.