Threshold photoelectron-photoion coincidence spectroscopy: dissociation dynamics and thermochemistry of Ge(CH3)4, Ge(CH3)3Cl, and Ge(CH3)3Br

Threshold photoelectron-photoion coincidence spectroscopy (TPEPICO) has been used to investigate the gas-phase ionic dissociation energies and thermochemistry of Me4Ge and Me3GeX, (Me = methyl; X = Cl, Br) molecules. The 0 K dissociation onsets for these species have been measured from the breakdown diagram and the ion time-of-flight distributions, which were modeled with the statistical RRKM theory and DFT calculations. The measured 0 K dissociative photoionization onsets were as follows: Me3Ge+ + Me (9.826 +/- 0.010 eV); Me3Ge+ + Cl (10.796 +/- 0.040 eV); Me3Ge+ + Br (10.250 +/- 0.011 eV); Me2GeCl+ + Me (10.402 +/- 0.010 eV); and Me2GeBr+ + Me (10.333 +/- 0.020 eV). These onsets were used to obtain new values for delta(f)H(degrees)298 (in kJ/mol) of the neutral molecules Me3GeCl (-239.8 +/- 5.7) and Me3GeBr (-196.5 +/- 4.3), and also for the following ionic species: Me3Ge+ (682.3 +/- 4.1), Me2GeCl+ (621.1 +/- 5.8), and Me2GeBr+ (657.8 +/- 4.7).     

Charge-induced unilamellar vesicle formation and phase separation in solutions of Di-n-decylmethylamine oxide

A double-tail amine oxide surfactant, di-n-decylmethylamine oxide (2C10MAO), was prepared, and the effects of protonation on aggregate structure were examined by small-angle neutron scattering (SANS), cryo-transmission electron microscopy (cryo-TEM), turbidity, electric conductivity, and solubilization of an oil-soluble dye at various degrees of neutralization, X, defined as the mole ratio of HCl/2C10MAO. The surfactant makes an L(2) phase in the nonprotonated state (X = 0) in water. The L(2) phase is in equilibrium with an aqueous L(1) phase. On protonation, unilamellar vesicles (ULVs) are formed over a wide range of compositions (0.05 < X< 0.4-0.5 at C = 10 mM) as observed by cryo-TEM. At X = 0.2, the ULV is stable over a wide concentration range (3 mM < or = C < 0.1 M), but an L(alpha) phase replaces the vesicle phase at C > 0.1 M. SANS results show that the mean radius of the ULV is about 25 nm and the bilayer thickness is about 2 nm, consistent with the extended configuration of the alkyl chains of the surfactant. An important contribution to the enhanced stability of the bilayer structures over the L(2) phase is suggested to be the translational entropy of the counterions. The enhanced stability of the bilayers diminishes as the counterion concentration increases either by an increase of X or by the addition of a salt. When the counterion concentration exceeds a critical value, the ULV solutions transform into the L(2) phase (or L(2)/L(1) two-phase system at low surfactant concentrations). The critical composition X is about 0.4-0.5 in water, but it is below 0.4 in D(2)O. The critical NaCl concentration is below 5 mM at X = 0.2. The stability of ULVs against multilamellar vesicles is ascribed partly to undulation forces and partly to the adjustable nature of the spontaneous curvature of amine oxide monolayers. The characteristics of the ULV of the surfactant remain the same within a temperature range 25-50 degrees C at X = 0.2. An iridescent lamellar phase and possibly an L(3) phase were observed in a very narrow X range (0 < X < 0.02) prior to the vesicle phase.     

Stereoselective Synthesis of Tetrasubstituted Alkenes via a Cp*CoIII-Catalyzed C−H Alkenylation/Directing Group Migration Sequence

A highly atom economical and stereoselective synthesis of tetrasubstituted α,β-unsaturated amides was achieved by a Cp*Co^III-catalyzed C−H alkenylation/directing group migration sequence. A carbamoyl directing group, which is typically removed after C−H functionalization, worked as an internal acylating agent and migrated onto the alkene moiety of the product. The directing group migration was realized with the Cp*Co^III catalyst, while a related Cp*Rh^III catalyst did not promote the migration process. The product was further converted into two types of tricyclic compounds, one of which had fluorescent properties.     

Development of a novel tablet machine for a tiny amount of powder and evaluation of capping tendency

A novel single punch tablet machine was developed for a tiny amount of powder sample. This tablet machine mainly consists of upper and lower punches, single die, and conical powder feeder equipped with micro-vibrators. By using the powder feeder, mass of discharged powder can be maintained constant even if a tiny amount of powder having poor flowability is used. Motions of both upper and lower punches can be set arbitrarily. Thus, this machine enables us to prepare tablets with a tiny amount of powder sample under the same compression mechanism as conventional rotary tablet machines. Performance of the developed tablet machine was evaluated in a continuous direct tableting using a model powder with poor flowability. Thirty-four tablets (195 mg×34) having acceptable properties can be successfully prepared using no more than 10.0 g of a powder sample. We then proposed a novel in-die evaluation method of capping tendency. A new phase diagram consisting of the elastic recovery energy and the plastic deformation energy was proposed. These energies were calculated from a force-displacement profile, continuously monitored by the developed tablet machine. The results indicate that by using the new diagram the capping tendency of tablets prepared from various model powders can be well discriminated. The developed tablet machine and proposed evaluation method can contribute to a significant cost reduction and speeding up of formulation studies of oral dosage form.     

Extraction capacity of diglycolamide derivatives for Ca(II), Nd(III) and Zr(IV) from nitric acid to N-dodecane containing a solvent modifier.

In order to evaluate the extraction property of new extractants, diglycolamide (DGA) compounds, we investigated the maximum extraction of di-, tri-, and tetravalent metal ions using nitric acid and n-dodecane. The limits of metal concentration (LOC) for Ca(II), Nd(III) and Zr(IV) in the organic phase are strongly influenced by HNO3 and the extractant concentration. For the purpose of enhancing the LOC value, we employed a modifier of the solvent, N,N-dihexyl-octanamide (DHOA) and DGA with a long alkyl chain, and examined the results. It was evident that LOC increased with the DHOA concentration and the length of the alkyl chain attached to the N atom of DGA. The stoichiometric values of LOC(Zr) estimated from the extraction reaction were confirmed by using the extraction condition: tetraoctyl-DGA/1 M DHOA + n-dodecane and 3 M HNO3.     

Novel Propagation Analysis of Coupled Waveguides by Coupled Mode Expansion and Segmentation

To optimize the coupling efficiency between the busline waveguide and the ring resonator in a vertically coupled microring resonator, we developed a new method using local normal modes and the segmentation along the propagation axis.     

Determination of oxycodone and hydrocotarnine in cancer patient serum by high-performance liquid chromatography with electrochemical detection.

We developed an HPLC procedure using electrochemical detection for the quantitation of oxycodone and hydrocotarnine in cancer patients serum. An eluent of methanol:acetonitrile:5 mM pH 8 phosphate buffer (2:1:7) was used for the mobile phase. The calibration curve was linear in the range from 10 ng/mL to 100 ng/mL. The recovery of oxycodone and hydrocotarnine was 97.2% and 90.5%, respectively. The relative standard deviations within-runs and between-runs for the assay of oxycodone or hydrocotarnine were less than 4.8%. The method developed here was better than the method reported previously.     

Characterization of polyether mixtures using thin-layer chromatography and matrix-assisted laser desorption/ionization mass spectrometry

Thin-layer chromatography (TLC) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) were combined to achieve characterization of polyether mixtures. Three polyethers, polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetramethylene glycol (PTMG), or mixtures of these compounds, were studied. One shortcoming of mixture analysis of synthetic polymers using MALDI-MS is that individual polymers in the mixture may display different detection sensitivities. For example, the MALDI mass spectrum of an equimolar mixture of PEG, PPG and PTMG displayed a high intensity of PPG ions, while no PTMG ions were detectable; however, PTMG ions were detected after the mixture had been separated by TLC. This combined TLC and MALDI-MS analysis of a PPG polymer bearing reactive epoxy groups showed that the polymer contained byproducts with different end-groups. These byproducts were identified as chloro-substituted polymers formed during polymer synthesis. Our study shows TLC to be a rapid and low-cost separation technique, and that it can be combined with MALDI-MS to achieve effective analysis of synthetic polymers.     

Semi‐online nanoflow liquid chromatography/matrix‐assisted laser desorption ionization mass spectrometry of synthetic polymers using an octadecylsilyl‐modified monolithic silica capillary column

We have designed a semi‐online liquid chromatography/matrix‐assisted laser desorption/ionization mass spectrometry (LC/MALDI‐MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI‐MS analysis. Our novel semi‐online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,‐hexafluoroisopropyl alcohol (HFIP), to be used to achieve cost‐effective analysis. Using the semi‐online LC/MALDI‐MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size‐exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed‐phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI‐MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size‐exclusion separation; the reversed‐phase separation by interaction with the ODS functions may have less influence on column separation. The semi‐online monolithic capillary LC/MALDI‐MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright © 2010 John Wiley & Sons, Ltd.