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排序方式: 共有801条查询结果,搜索用时 15 毫秒
81.
Kenji Yoshikawa Miki Shimizu Toshiro Matsumura Akio Sakuragawa 《International journal of environmental analytical chemistry》2018,98(8):789-798
Capillary zone electrophoresis with indirect UV detection was developed for the simultaneous analysis of inorganic anions and organic acids using a mixed solution of 2,6-pyridinedicarboxylic acid and cetyltrimethylammonium hydroxide as the background electrolyte (BGE). The parameters which influence the separation, such as indirect UV detection wavelength, BGE conditions, applied voltage and extraction conditions were investigated. Thirteen inorganic anions and organic acids were detected within 20 min. The calibration curves of each analyte were linear with correlation coefficients greater than 0.991. The relative standard deviations (n = 10) of the peak areas ranged from 0.6% to 3.3%. The detection limits for these species ranged from 0.4 to 1.4 mg/L at a signal-to-noise ratio of 3. The recovery rate of each analyte was more than 80% under optimised extraction conditions, except for nitrite. The proposed method was applied towards the analysis of inorganic anions and organic acids in the atmospheric particulate matter using an Andersen sampler. The particle size of the particulate matter was determined, but not the size of the anions. 相似文献
82.
Masayuki Yoshikawa Yoshiharu Ikeda Hiroshi Kayakiri Kohei Takenaka Isao Kitagawa 《Tetrahedron letters》1982,23(45):4717-4720
By use of a decarboxylation reaction with lead tetraacetate and a deacetoxylation reaction with sodium borohydride as key-reactions, paromamine ( and tri-N-benzyloxycarbonylparomamine () were synthesized from D-glucosamine. 相似文献
83.
84.
Hirota J Satomi Y Yoshikawa K Takao T 《Rapid communications in mass spectrometry : RCM》2003,17(5):371-376
Epsilon -N,N,N-trimethyllysine (K(me3)) is a component of a number of proteins and plays an important role in the expression of their biological functions. Trimethylation, which causes an incremental increase in mass of 42.0470 Da from that of the corresponding MH(+) ion, cannot be distinguished from the acetylation (+42.0106 Da), which also occurs on epsilon-amino groups of Lys or alpha-amino groups in many proteins, without high-accuracy mass measurement which is accurate to within the second decimal place. MALDI-MS and MS/MS have been applied for the analyses of post-translational modifications of histone H3, which is known to contain both multiple acetylation and methylation sites in its sequence. During the measurements of the modified peptides, a novel fragmentation which involves the loss of trimethylamine from K(me3) was found. This characteristic fragmentation, which was observed to produce ions separated by 59 Da from the conventional precursor ion or sequence ions, would be useful for probing K(me3) units in the sequence. 相似文献
85.
Taguchi Y Ohtani H Tsuge S Ishida Y Kimura K Yoshikawa T 《Journal of chromatography. A》2003,993(1-2):137-142
Highly sensitive and specific determination of trace amounts of a polymeric hindered amine light stabilizer (HALS) in polypropylene (PP) materials could be established by improving reactive thermal desorption-gas chromatography (RTD-GC) in the presence of an organic alkali, tetramethylammonium hydroxide. By using nitrogen-phosphorus detection, highly selective detection of the HALS-related components was attained. In addition, the use of a polar poly(ethylene glycol) separation column alleviated the adsorption of minor specific pyrolysis products. This modified RTD-GC method allowed the determination of the polymeric HALS (Mr 1900) in PP even for trace concentrations between 100 and 500 ppm, through observing selectively the characteristic products containing a tetramethylpiperidine moiety, which had been impossible to detect under the previous RTD-GC conditions using a non-polar separation column and conventional flame ionization detection. 相似文献
86.
Haruhiko Aoi Michihiro Ishimori Sadao Yoshikawa Teiji Tsuruta 《Journal of organometallic chemistry》1975,85(2):241-248
An optically active Co(I)(salen) type complex, lithium N,N′-bis(salicylaldehyde)-1(R), 2(R)-1,2-trans-cyclohexanediiminatocobalt(I), was prepared by reducing the CoII complex, N,N′-bis(salicylaldehyde)-1(R),2(R)-1,2-trans-cyclohexanediiminatocobalt(II), with LiAlH4. The structure of the CoI complex was determined on the basis of the structure of the corresponding CoII complex and was confirmed by usual physicochemical methods. Furthermore, characteristics of the absorption and circular dichroism(CD) spectra of the CoI complex were compared with those of the reported structure of Na+[Co(I)(salen)]?. Highly asymmetric selectivity was found in a resolution reaction of DL-propylene oxide by use of the above optically active lithium cobalt(I) complex as a catalyst. 相似文献
87.
88.
Effect of solvent composition on chiral recognition ability of molecularly imprinted DIDE derivatives. 总被引:2,自引:0,他引:2
In the present study, molecularly imprinted materials from the tetrapeptide derivative, H-Asp(OcHex)-Ile-Asp(OcHex)-Glu(OBzl)-CH2-, were adopted as samples to study the effect of the polarity of the environment on the chiral (molecular) recognition ability. The optimum composition, with the best chiral recognition, is a 50 vol% aqueous ethanol solution. 相似文献
89.
Masakazu Yoshikawa Katsunori Koso Kyoichi Yonetani Satoshi Kitamura Satoshi Kimura 《Journal of polymer science. Part A, Polymer chemistry》2005,43(2):385-396
Molecularly imprinted polymeric membranes were prepared from various oligopeptide tweezers by the adoption of N‐α‐tert‐butoxycarbonyl‐D ‐tryptophan (Boc‐D ‐Trp) or N‐α‐tert‐butoxycarbonyl‐L ‐tryptophan (Boc‐L ‐Trp) as a print molecule. The chiral recognition ability of the formed molecular recognition sites was dependent on the absolute configuration of the print molecule adopted in the membrane preparation (molecular imprinting) process, whereas the candidate oligopeptide tweezers consisted of the L ‐amino acid residues. In other words, the membranes imprinted by the D ‐isomer recognized the D ‐isomer in preference to the corresponding L ‐isomer, and vice versa. The affinity constant between the target molecule and the chiral recognition site from the oligopeptide tweezers was higher than that from a single‐strand oligopeptide derivative. Those membranes selectively transported the enantiomer, which was preferentially incorporated into the membrane by dialysis. The permselectivities for these membranes exceeded their adsorption selectivities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 385–396, 2005 相似文献
90.
Pumir A Nikolski V Hörning M Isomura A Agladze K Yoshikawa K Gilmour R Bodenschatz E Krinsky V 《Physical review letters》2007,99(20):208101
The effectiveness of chaos control in large systems increases with the number of control sites. We find that electric field induced wave emission from heterogeneities (WEH) in the heart gives a unique opportunity to have as many control sites as needed. The number of pacing sites grows with the amplitude of the electric field. We demonstrate that WEH has important advantages over methods used in clinics, and opens a new way to manipulate vortices in experiments, and potentially to radically improve the clinical methods of chaos control in the heart. 相似文献