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201.
Jinmao You Xiangming Chen Xianen Zhao Yourui Suo Honglun Wang Yulin Li Jing Sun 《Chromatographia》2006,63(7-8):337-343
A pre-column derivatization method for the sensitive determination of amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl
chloroformate (BCIC-Cl) followed by high-performance liquid chromatography with fluorescence detection has been developed.
Identification of derivatives is carried out by high performance liquid chromatography/atmospheric pressure chemical ionization
(LC-APCI-MS-MS). The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent is replaced by 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl
functional group, which results in a sensitive fluorescence derivatizing reagent BCIC-Cl. BCIC-Cl can easily and quickly label
amines. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography and show an intense
protonated molecular ion corresponding m/z [MH]+ under APCI in positive-ion mode. The collision-induced dissociation of protonated molecular ion formed a product at m/z 260 corresponding to the cleavage of CH2-OCO bond. Studies on derivatization demonstrate excellent derivative yields over the pH 9.0–10.0. Maximal yields close to
100% are observed with a 3 to 4-fold molar reagent excess. In addition, the detection responses for BCIC derivatives are compared
with those obtained using CEOC and FMOC as derivatization reagents. The ratios of IBCIC/ICEOC and IBCIC/IFMOC are, respectively, 1.23–3.14 and 1.25–3.08 for fluorescent (FL) responses (here, I is relative fluorescence intensity). Separation of the derivatized amines had been optimized on reversed-phase Eclipse XDB-C8 column. Detection limits are calculated from 1.0 pmol injection, at a signal-to-noise ratio of 3, are 10.6–37.8 fmol. The
mean interday accuracy ranges from 94 to 105% for fluorescence detection with the largest mean %CV<7.5. The mean interday
precision for all standards is < 6.0% of the expected concentration. Excellent linear responses are observed with coefficients
of > 0.9997.
Revised: 12 December 2005 and 13 Febrauary 2006 相似文献
202.
H. Saglam T. Gozler B. Kivcak B. Demirci K. H. C. Baser 《Chemistry of Natural Compounds》2001,37(5):439-441
The chemical composition of the essential oil ofHaplophyllum myrtifoliumBoiss., endemic to Turkey, was examined by GC/MS. Ninety-seven compounds were characterized with linalool (12.8%), -caryophyllene (10.3 %), and methyleugenol (5.9 %) as the main constituents. 相似文献
203.
204.
S-Alkylation of 2-acetamido-9-(2-acetoxyethoxymethyl)-6-oxo-8-thioxopurine was used to synthesize its novel S- and N(7)-substituted derivatives. We have established the effect of the structure of the alkylating agent on the reaction conditions and its regioselectivity. We have shown that the synthesized guanine derivatives can be modified further. 相似文献
205.
《Surface and interface analysis : SIA》2003,35(8):667-672
The individual and combined adsorption behavior of polyamides and two different silanes to multicomponent glass surfaces was probed with a combination of x‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and static contact angle measurements. Samples were analyzed with and without solvent rinsing to separate the weakly bound (physisorbed) and more strongly bound (chemisorbed) species. High‐resolution XPS on N 1s revealed that the polyamides adsorb to the glass surfaces via protonated amine species at the acidic (OH) sites on the glass surface. Angle‐resolved XPS confirmed this by showing that the alkyl portion of the polymer is oriented away from the glass interface. In competitive coadsorption studies it was found that amino‐terminated silanes preferentially adsorb to the glass surface, relegating the polyamide to a physisorbed outer layer. When mercaptoterminated silanes were competitively coadsorbed the polyamide was preferentially adsorbed even when present at a concentration twenty times less than that of the silane. Altogether, this work reveals the strong interaction between surface silanols and amino‐functionalized organics. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
206.
E. Yu. Mikhteeva E. G. Savchuk E. A. Tararako E. B. Merkulov V. K. Goncharuk 《Journal of Structural Chemistry》2005,46(6):1082-1085
Images of cleaved surfaces were obtained for 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF (ZBLAN) glasses and fused quartz using an NTMDT atomic force microscope. It is shown that the scatter of particle size depends on the cooling rate and is 21–48.5 Å for the cleaved surface of ZBLAN glass obtained by very fast cooling and 68–172 Å for the cleaved surface of ZBLAN after slow cooling. For cleaved fused quartz, the range is 25-18 Å. 相似文献
207.
F. I. Zubkov E. V. Nikitina K. F. Turchin A. A. Safronova R. S. Borisov A. V. Varlamov 《Russian Chemical Bulletin》2004,53(4):860-872
The intramolecular Diels—Alder reaction of readily accessible 4-substituted 4-(N-furfuryl)aminobut-1-enes was studied and a new one-step method was developed for the synthesis of 6,8a-epoxy-1,2,3,4,4a,5,6,8a-octahydroisoquinoline (3-aza-11-oxatricyclo[6.2.1.01,6]undec-9-ene) derivatives. The [4+2]-cycloaddition proceeds stereoselectively to form exo-adducts. The influence of substituents at the nitrogen atom in 4-(N-furfuryl)aminobut-1-enes on the cycloaddition pathway was examined. 相似文献
208.
Yasuo Saegusa Takahiro Kato Hirotaka Oshiumi Shigeo Nakamura 《Journal of polymer science. Part A, Polymer chemistry》1992,30(7):1401-1406
Novel polyaryloxydiphenylsilanes with reduced viscosities of 0.31–0.65 dL/g were obtained by the melt polycondensation of dianilinodiphenylsilane with three bisphenols, 2,2-bis (4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane, 3 (4-hydroxyphenyl)-1,1,3-trimethyl-5-indanol, and 9,9-bis (4-hydroxyphenyl) fluorene, at 200–320°C in vacuo. These polymers are all amorphous and readily soluble in a wide variety of organic solvents such as chlorinated and aromatic hydrocarbons, cyclic ethers, and polar aprotic solvents. Because of their bulky and/or rigid ring structures, polyaryloxydiphenylsilanes containing diphenylhexafluoropropane, phenylindane, and diphenylfluorene units in the main chain have high glass transition temperatures of 106, 112, and 172°C, respectively. They are thermally stable showing almost no weight loss up to 350°C in air. Colorless, transparent, but brittle films are obtained from these polymers by solution casting. Ultraviolet transmission is sharply cut off by these polyaryloxydiphenylsilane films at ca. 300 nm, and the cut-off wavelength depends on the bisphenols used. 相似文献
209.
Improved separations of the isomers of olefinic aliphatic insect pheromones were obtained on cholesteryl cinnamate glass capillary columns by operating in the supercooled temperature range of the liquid crystal. Capillary columns were prepared with varying film thickness of the stationary phase; choice of the correct film thickness ensured optimum retention for a wide range of compounds within the most effective temperature range of the liquid crystal. The deactivation procedures described made the liquid crystal columns suitable for separation of the geometric isomers of polar and nonpolar compounds. 相似文献
210.
Ahmed M. El-Sayed Esmat M. A. Hamzawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(9):1119-1125
Summary. The magnetic and microstructure properties of Fe2O3–0.4NiO–0.6ZnO–B2O3 glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni0.4Zn0.6-Fe2O4 crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature
of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and
3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer.
The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging
from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples
were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with
saturation magnetization ranging from 12.25 to 17.82 emu/g. 相似文献