Development of an ion attachment mass spectrometer for direct detection of intermediates in combustion flames

A system with Li+ ion attachment (IA) ionization has been developed for the direct detection of intermediates formed in burning flames by mass spectrometry. Dimethyl ether (DME) among alternative fuels was selected as a test substance to examine the capability of the system. As a result, intermediates generated in a premixed DME-air flame were directly detectable as Li+ adduct ions. By moving the burner on an X-Y stage, spatial distribution profiles of different species, including unburned DME and formaldehyde, were obtained for three types of flames: diffusion, partially premixed, and premixed.     

Precolumn fluorescence labeling method for simultaneous determination of hydroxyzine and cetirizine in human serum

A highly selective and sensitive method was developed for simultaneous determination of the antihistaminic drug hydroxyzine (HZ) and its pharmacologically active metabolite cetirizine (CZ) in human serum using haloperidol as internal standard. The method was based on fluorescence labeling of both drugs with a fluorescent arylboronic acid 4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl boronic acid followed by separation on silica column using a mobile phase consisting of acetonitrile and water (90:10, v/v%) containing triethylamine and acetic acid. The labeling reaction conditions were optimized and the liquid-liquid extraction method was successfully applied to extract the both drugs from serum. The linearity range was 0.025-2.00 microg/mL for HZ and CZ. The limit of detection (S/N = 3) was 10 and 5 ng/mL for HZ and CZ, respectively.     

Diversification of self-organized architectures in supramolecular dye assemblies

Upon complexation with bismelamine receptors (BMn) featuring different alkyl linker lengths (number of methylene groups (n) = 5-12), a barbituric acid merocyanine dye (1) can be loaded into diverse self-organized superstructures through multiple hydrogen-bonding interactions. UV/vis, dynamic light scattering, and NMR studies in cyclohexane demonstrate that the diversification of the primarily formed hydrogen-bonded species in solution occurs by varying the linker length of BMn. Hierarchical organization of the hydrogen-bonded species is achieved by slow evaporation of the solvent (forming solvent-free films), and the resulting superstructures are evaluated by polarized optical microscopy, X-ray diffraction, SEM, and AFM techniques. The formation of columnar structures with and without two-dimensional ordering are revealed for shorter (n = 5-7) and longer (n = 11, 12) linker bis(melamines), respectively. On the contrary, in the cases of n = 8-10, the formation of lamellar structures is unveiled. Several assemblies (n = 5, 7, 11) indicate the formation of a liquid crystalline mesophase in POM and DSC analyses. Hierarchical organization is also achieved in solution by prolonged aging, affording phase-separated crystalline nanofibers (n = 5, 7) and soft nanofibrils agglomerating into wormlike objects (n = 8), gel-forming continuous globular networks (n = 10), and nanofibers (n = 11, 12). These superstructural and morphological diversifications are an outcome of the variation in the primarily formed hydrogen-bonded supramolecular architectures. Using this strategy, diverse self-assembled materials will be obtained from a single dye component.     

First investigation at elevated pressures to confirm the exact nature of the gated electron-transfer systems: volume profiles of the gated reduction reaction and nongated reverse oxidation reaction involving a [Cu(dmp)2(solvent)]2+/[Cu(dmp)2]+ couple (dmp = 2,9-dimethyl-1,10-phenanthroline)

Redox reactions involving the [Cu(dmp)2]2+/+ couple (dmp = 2,9-dimethyl-1,10-phenanthroline) in acetonitrile were examined at elevated pressures up to 200 MPa. Activation volumes were determined as -8.8 and -6.3 cm3 mol-1 for the reduction cross-reaction by [Co(bipy)3]2+ (bipy = 2,2'-bipyridine) and for the oxidation cross-reaction by [Ni(tacn)2]3+ (tacn = 1,4,7-triazacyclononane), respectively. The activation volume for the hypothetical gated mode of the self-exchange reaction estimated from the reduction cross-reaction was -13.9 cm3 mol-1, indicating extensive electrostrictive rearrangement of solvent molecules around the CuII complex during the change in the coordination geometry before the electron-transfer step. On the other hand, the activation volume for the self-exchange reaction estimated from the oxidation cross-reaction was -2.7 +/- 1.5 cm3 mol-1. Although this value was within the range that can be interpreted by the concept of the ordinary concerted process, from theoretical considerations it was concluded that the reverse (oxidation) cross-reaction of the gated reduction reaction of the [Cu(dmp)2(CH3CN)]2+/[Cu(dmp)2]+ couple proceeds through the product excited state while the direct self-exchange reaction between [Cu(dmp)2(CH3CN)]2+ and [Cu(dmp)2]+ proceeds through an ordinary concerted process.     

A simple and highly selective fluorescent sensor for palladium based on benzofuran-2-boronic acid

Benzofuran-2-boronic acid could be used as a fluorescent sensor for the detection of Pd²⁺ because it was rapidly converted to highly fluorescent derivative after mixing with Pd²⁺ under basic condition at room temperature. We found that dimerization of benzofuran was occurred to form fluorescent derivative by the catalytic activity of palladium. The fluorescence intensity at 360 nm increased with increasing the concentration of Pd²⁺. The excellent selectivity for Pd²⁺ was demonstrated among other metal ions. Based on this findings, we successfully applied benzofuran-2-boronic acid to develop a microplate-based assay for high-throughput measurement of Pd²⁺. The detection limit (blank + 3SD) for Pd²⁺ of the proposed assay was 9.8 nM.     

Poly(l‐lactic acid)‐modified silica stationary phase for reversed‐phase and hydrophilic interaction liquid chromatography

Poly(l ‐lactic acid) is a linear aliphatic thermoplastic polyester that can be produced from renewable resources. A poly(l ‐lactic acid)‐modified silica stationary phase was newly prepared by amide bond reaction between amino groups on aminopropyl silica and carboxylic acid groups at the end of the poly(l ‐lactic acid) chain. The poly(l ‐lactic acid)‐silica column was characterized in reversed‐phase liquid chromatography and hydrophilic interaction liquid chromatography with the use of different mobile phase compositions. The poly(l ‐lactic acid)‐silica column was found to work in both modes, and the retention of test compounds depending on acetonitrile content exhibited “U‐shaped” curves, which was an indicator of reversed‐phase liquid chromatography/hydrophilic interaction liquid chromatography mixed‐mode retention behavior. In addition, carbonyl groups included into the poly(l ‐lactic acid) backbone work as an electron‐accepting group toward a polycyclic aromatic hydrocarbon and provide π–π interactions.     

Labeling of alprenolol with fluorescent aryl iodide as a reagent based on Mizoroki-Heck coupling reaction

A novel fluorescent labeling method for alprenolol was developed based on Mizoroki-Heck coupling reaction. We designed and synthesized fluorescent aryl iodide, 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) as a labeling reagent. DIBI has a lophine skeleton carrying an iodide atom acting as fluorophore and reactive center, respectively. In order to evaluate the usefulness of DIBI, a high-performance liquid chromatography (HPLC) with fluorescence detection method was developed for the determination of alprenolol as a model compound of terminal double bond. The fluorescent labeling of alprenolol with DIBI was achieved in the presence of palladium acetate as a catalyst, and the labeled alprenolol was detected fluorometrically. In addition, it was found that the fluorescence of DIBI derivative increased and red shifted when compared with that of DIBI. Furthermore, the proposed method could be applied to determine the alprenolol concentration in rat plasma after administration of alprenolol without interferences from biological components. The detection limit (S/N=3) for alprenolol in rat plasma was 0.74 ng/mL (30 fmol on column).     

GC-MS ultra trace analysis of dioxins produced through hydrothermal gasification of biowastes

Hydrogen gas and the valuable material hydroxylapatite have successfully been produced from biomass wastes by hydrothermal gasification. However, it was expected that toxic compounds might be produced through the reaction. It was therefore important to clarify whether toxic compounds were synthesized in hydrothermal gasification of biowastes since dioxins are categorized among the most toxic compounds for humans. This is particularly true of biomass wastes containing hetero-atoms in organic matrices. In this study, formation of the dioxins polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and certain dioxin-like polychlorinated biphenyls (PCBs) were examined. Chicken manure and cattle manure were tested as real biowastes for hydrothermal gasification and the produced compounds in the liquid and solid phases were analyzed for detection of dioxins by gas chromatography/mass spectrometry (GC/MS). The total toxic equivalent quantities (the total TEQ) of dioxins produced by the hydrothermal gasification were found to be much lower than regulation levels in Japan require and therefore the products require no additional post treatments.     

Two-Photon Laser-Induced Fluorescence Spectra of Argon in a Grimm-Style Glow Discharge Tube

Two-photon excited laser-induced fluorescence (LIF) spectra of argon atom were successfully observed in a Grimm-style glow discharge tube, which has widely been applied to depth profiling of the elemental composition on various film-like samples by emission spectrometry. The LIF signal of an argon atomic line at 641.63 nm was observed when the glow discharge argon plasma was illuminated by a pulsed Ti:sapphire laser radiation of 7–10 mJ/pulse at 753.39 or 795.66 nm without focusing of the laser beam.