Evaluation of supercritical fluid extraction for isotope dilution gas chromatography-mass spectrometric quantification of polychlorinated biphenyls in sediment.

Supercritical fluid extraction (SFE) has been evaluated as an extraction technique for the isotope-dilution quantification of polychlorinated biphenyls (PCBs) in a sediment sample. A high-resolution mass-spectrometric system equipped with a gas chromatograph was employed for the determination of seven target PCB congeners. The effect of the operation parameters on the SFE efficiency was investigated, in which the analytical values of five target PCB congeners significantly increased with increases in the extraction temperature and pressure, and that of 4,4'-dichlorobiphenyl further increased by applying static extraction. The following conditions were found to be optimal: extraction temperature, 140 degrees C; pressure, 30 MPa; time and mode, static for 15 min then dynamic for 30 min. Under these conditions, the addition of modifiers influenced the extraction of polar compounds, but did not affect the analytical values of the PCB congeners. The optimized method was suitable for high-throughput analysis as well as for providing accurate analytical results, which were comparable to or better than the analytical results obtained by Soxhlet extraction.     

Simultaneous determination of trimethyl-and triethyllead in urban dust by species-specific isotope dilution/gas chromatography-inductively coupled plasma mass spectrometry

Both (206)Pb-labeled trimethyllead (TML) and triethyllead (TEL) were synthesized from (206)Pb-enriched metallic Pb certified reference material (NIST SRM 983) and iodomethane or iodoethane through a one-process reaction in a closed system using centrifuge tubes, respectively. Organolead compounds in an urban dust reference material (BCR CRM 605) were extracted with an acetic acid/methanol (1:1) solution, which was mechanically shaken for 24 h. After adjusting the pH of the extracted solution to pH 5, the extracted organolead compounds were derivatized by tetrabutylammonium tetrabutylborate (TATB) and measured with GC-ICPMS. The analytical results of TML and TEL for BCR CRM 605 were 8.22 +/- 0.04 microg kg(-1) (mean +/- standard deviation, n = 3) and 1.12 +/- 0.06 microg kg(-1), respectively. The analytical results of TML agreed well with the certified value (7.9 +/- 1.2 microg kg(-1)).     

Highly diastereoselective arylations of substituted piperidines

A highly diastereoselective methodology for the preparation of various substituted piperidines via Negishi cross-couplings with (hetero)aryl iodides was developed. Depending on the position of the C-Zn bond relative to the nitrogen (position 2 vs position 4), the stereoselectivity of the coupling can be directed toward either the trans- or cis-2,4-disubstituted products. Density functional theory calculations on the relative stabilities of the Zn and Pd intermediates were performed to explain the high diastereoselectivities obtained. A novel 1,2-migration of Pd further expands this method to the stereoselective preparation of 5-aryl-2,5-disubstituted piperidines.     

Development of dry salbutamol sulfate powder with high inhalation performance independent of inhalation patterns

While dry powder inhalations are commonly used to treat pulmonary diseases, their clinical performance depends on patient inspiratory flow patterns. The purpose of this study was to develop a new powder with high and stable therapeutic performance for various patients. We applied the supercritical antisolvent (SCF) method to salbutamol sulfate (SS) to prepare a bulky SS particle (SS-SCF). Tests of in vitro inhalation performance with a human inspiratory flow simulator revealed SS-SCF to be less susceptible to inspiratory flow patterns than milled SS. When inspired, the unique structure seemed to be broken resulting in small fragments that could be delivered to the lungs. However, stability tests under physical stress showed tolerance for transportation and handling. In addition, optimization of the concentration of the SS solution applied to SCF method improved the in vitro inhalation performance of SS-SCF. These results indicated that a unique bulky SS powder prepared by the SCF method was useful for dry powder inhalation.     

Design,Synthesis and Physical Properties of New Liquid Crystal Materials for Active Matrix LCD (1)

Abstract

Liquid crystal materials having a decahydronaphthalene ring structure were designed for active matrix LCD and were prepared by hydrogenation of the ocatahydronaphthalenes obtained through the reaction of a fluorinated phenyl magnesium bromide with the 6-alkyl-decahydronaphthalen-2-ones and followed by dehydration. These compounds exhibit wide nematic temperature ranges with low melting points and very low birefringences. These results are useful for design of new liquid crystal mixtures for TFT-displays.     

Development of vial wall sorptive extraction and its application to determination of progesterone in human serum

A novel sample preparation method, vial wall sorptive extraction (VWSE), which uses a vial whose internal wall is coated with polydimethylsiloxane (PDMS), was developed. The method was applied to the determination of progesterone in human serum sample. Human serum sample (0.5 mL) spiked with progesterone-¹³C₂ was pipetted into the VWSE device and vortex mixing was performed for 30 min. Then, the serum sample was removed and the vial rinsed with purified water. Fifty microliter of methanol as liquid desorption (LD) solvent was pipetted into the VWSE device and vortex mixing was performed for 10 min. Then, the extract was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The correlation coefficient (r) of the calibration curve over the concentration range of 0.5–200 ng mL⁻¹ was 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1 and 0.5 ng mL⁻¹, respectively. The relative recoveries were 97.9% (RSD: 4.4%, n = 6) and 102.8% (RSD: 1.1%, n = 6) for progesterone spiked at 5 and 50 ng mL⁻¹, respectively. This simple, accurate, sensitive, and selective analytical method is applicable to the trace analysis of a minute amount of sample.     

Correlation of crystal structures with electric field gradients in the fluorite- and pyrochlore-type compounds in the Gd2O3-ZrO2 system

Correlation of crystal structure with electric field gradient (EFG) in the fluorite- and pyrochlore-type compounds in the Gd₂O₃-ZrO₂ system Gd_xZr_1−xO_2−x/2 with 0.18?x?0.62 were investigated by ¹⁵⁵Gd Mössbauer spectroscopy, powder X-ray diffraction and point-charge model (PCM) calculation. An intermediate ordered pyrochlore phase forms for 0.45?x?0.55, sandwiched with a disordered fluorite phase for 0.18?x<0.45 and 0.55<x?0.62. Some ¹⁵⁵Gd Mössbauer parameters, especially the quadrupole coupling constant (e²qQ), were found to exhibit a characteristic maximum around the ideal-pyrochlore Gd₂Zr₂O₇ (x=0.50) composition. The validity of the proposed pyrochlore-based structural model was examined by comparing the experimental values of EFG at the Gd sites with those calculated by the PCM calculations.     

In situ investigation of coadsorption of myoglobin and methylene blue to hydrophilic glass by broadband time-resolved optical waveguide spectroscopy

Recently, we have developed a broadband optical waveguide (OWG) spectrometer by using commercially available glass plates of tens of micrometers in thickness as the substrate-free multimode waveguides (Qi et al. Opt. Lett. 2002, 27, 2001-2003). The spectrometer having a bandwidth from 360 to 800 nm is capable of simultaneously detecting the Soret-band absorption of heme proteins and the visible absorption of organic dyes. In this article, the spectrometer was used to in situ investigate coadsorption of methylene blue (MB) and myoglobin from the mixed aqueous solution onto bare glass. Both MB and myoglobin in the mixed solution are positively charged, which makes them not only avoid the chemical interaction between each other but also easy to adsorb to hydrophilic glass. It was found that the coadsorption of MB and myoglobin occurred just in the early stage and the glass surface was finally occupied by myoglobin. The OWG spectroscopic investigation into the respective MB and myoglobin adsorptions shows that MB adsorption is reversible to some degree but that of myoglobin is irreversible. It reveals that the electrostatic binding of myoglobin to bare glass is stronger than the case of MB. Therefore, the adsorbed MB can be substituted by myoglobin. Moreover, via the electrostatic repulsion the tightly immobilized myoglobin prevents bulk MB from occupying the empty surface sites. It is the reason MB is absent from the hydrophilic glass coated with a submonolayer of myoglobin. In the article, we explained both the strong dimerization of MB at the interface and a slow decrease with time of the Soret-band absorbance after its maximum was reached. We also estimated the myoglobin coverage based on the waveguide theory. The study shows the distinguished applicability of the broadband OWG spectroscopy for in situ, real-time monitoring of the dye-protein coadsorption to silica from the mixed solution.     

A novel total synthesis of elaeocarpus alkaloids

The novel synthesis of elaeocarpus alkaloids has been achieved employing 1,3-dipolar cycloaddition reaction as a key step.