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51.
Yu-Ping Zhang Kwang-Pill Lee Hyun-Joo Noh Ali Md Showkat Seong-Ho Choi 《Microchemical Journal》2004,78(2):99-106
An appropriate optimization strategy should be used to find a desired resolution or selectivity with a minimum number of experiments in a limited time, which could assure the baseline separation of all target compounds. It was usually realized by means of a specialized computer program. In this paper, mapping optimization method and overlapping resolution mapping were compared for the optimization of a reversed-phase high-performance liquid chromatography (HPLC) isocratic separation of neutral compounds. The calculated resolutions and separation time of 7 to 10 experiments are fitted by different equations, which were used to build a contour plot with a minimum effective resolution and maximum retention time as a function of a mobile phase composition. The balance between resolution and analysis time could be easily realized by the overlapping of the final overlapping resolution mapping and analysis time mapping. The validity of the two methods was confirmed by some typical experiments. The models are simple, visual, and common without theoretical arithmetic. 相似文献
52.
Akhtaruzzaman M Kamata N Nishida J Ando S Tada H Tomura M Yamashita Y 《Chemical communications (Cambridge, England)》2005,(25):3183-3185
Dithiazolylbenzothiadiazoles easily obtained have high electron affinity and the FET device of a trifluoromethylphenyl derivative exhibited a good n-type performance with high electron mobility. 相似文献
53.
An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results. [Reaction: see text] 相似文献
54.
Hamed M. Abu El-Nader 《Transition Metal Chemistry》1995,20(3):316-319
Summary The kinetics of the thermal decomposition of thetris-oxalactocobaltate(III) complex has been investigated in the presence of EtOH and (CH2OH)2 spectrophotometrically in the 50–70 ± 0.1 ° C range. The rate of the reaction decreases upon the addition of either of the alcohols to the reaction medium, whereas the activation energy increases. The thermodynamic parameters were calculated and are discussed in terms of the solvation effects. The influence of the dielectric constants of the solvent mixtures on the rate has been studied. A free radical mechanism is proposed and discussed. 相似文献
55.
Gaber M. Abu El-Reash 《Transition Metal Chemistry》1993,18(5):493-496
Summary The synthesis and characterization of CrIII, MnII, FeIII, CoII, NiII, CuII, ZnII, CdII and UO
inf2
sup2+
complexes of N-isonicotinamido-N-benzoylthiocarbamide (H2IBTC) are reported. I.r. spectral data show that the ligand behaves in a bidentate, tridentate and/or tetradentate manner. Different stereochemistries are proposed for CrIII, MnII, FeIII, CoII, NiII and CuII complexes on the basis of spectral and magnetic studies. The i.r. data indicate that the carbonyl oxygen of the benzoyl moiety is the backbone of chelation in most complexes. 相似文献
56.
The complexes of the reagent 5-Br-PADAP with the metal ions La(III), Ce(III), and Y(III) have been studied.The composition and stability of these complexes have been determined. A sensitive spectrophotometric procedure for the determination of the metal ions La(III), Ce(III), and Y(III) has been proposed. The limitations of this procedure and the effect of other ions have been studied. 相似文献
57.
Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide
A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly‐5, 2′: 5′, 2″‐terthiophine‐3‐carboxylic acid), poly‐TTCA through the formation of amide bond between carboxylic acid groups of poly‐TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly‐TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X‐ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly‐TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73 s?1. The biosensor efficiently detected xanthine through oxidation at +0.35 V and reduction at ?0.25 V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10?6?1.0×10?4 M and 5.0×10?7 to 1.0×10?4 M, respectively. The detection limits were determined to be of 1.0×10?6 M and 9.0×10?8 M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. 相似文献
58.
Till?R?hrich Bassam?Abu Thaher Nico?Manicone Hans-Hartwig?OttoEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(8):979-999
Summary. (RS)-2-tert-Butyldimethylsilyl-1,2-thiazetidine-3-acetic acid 1,1-dioxide prepared from (RS)-S-benzyl--homocysteine was condensed via DCC/NHS with various L-amino acid esters or dipeptide esters yielding N-silylated -sultam peptides. A -sultam active ester was isolated as an intermediate. Desilylation with TBAF in THF yielded stable N-unsubstituted products, and deprotection of the benzyl esters was achieved by catalytic hydrogenation. (S)-S-Benzyl--homocysteine was obtained by fractional crystallization of the brucine salt of the racemate and transformed into benzyl (S)-1,2-thiazetidine-3-acetate, which was on the other hand synthesized by an enantiospecific route from -benzyl Boc-L-aspartate. Some -sultam peptides were prepared from the (S)-enantiomer, and finally some -sultam peptides containing D-Ala units were obtained. 相似文献
59.
Two-dimensional capillary electrophoresis was used for the separation of proteins and biogenic amines from the mouse AtT-20 cell line. The first-dimension capillary contained a TRIS–CHES–SDS–dextran buffer to perform capillary sieving electrophoresis, which is based on molecular weight of proteins. The second-dimension capillary contained a TRIS–CHES–SDS buffer for micellar electrokinetic capillary chromatography. After a 61-s preliminary separation, fractions from the first-dimension capillary were successively transferred to the second-dimension capillary, where they further separated by MECC. The two-dimensional separation required 60 min. 相似文献
60.
Noorjahan Begum Amarash C. Ghosh Shariff E. Kabir Md. Arzu Miah G.M. Golzar Hossain 《Polyhedron》2005,24(18):3074-3081
Four triosmium carbonyl clusters bearing terminal pyrazines, bridging hydroxy and methoxycarbonyl ligands of general formula [Os3(CO)9(μ-OH)(μ-OMeCO)L] (1, L = pyrazine; 2, L = 2-methylpyrazine; 3, L = 2,3-dimethylpyrazine; 4, L = 2,3,5-trimethylpyrazine) were synthesized by the reactions of [Os3(CO)12] with the corresponding pyrazine derivatives and water in the presence of a methanolic solution of Me3NO in moderate yields. Compounds [Os3(CO)9(μ-OH)(μ-OMeCO)L] react with a series of two electron donor ligands, L′ at ambient temperature to give [Os3(CO)9(μ-OH)(μ-OMeCO)L′] (5, L′ = PPh3; 6, L′ = P(OMe)3; 7, L′ = tBuNC; 8, L′ = C5H5N) in good yields by the displacement of the pyrazine ligands. This implies that the pyrazine ligands in 1–4 are relatively labile. Compounds 2, 3, 4, and 8 were characterized by single crystal X-ray diffraction analyses. All the four compounds possess two metal–metal bonds and a non-bonded separation of two osmium atoms defined by Os(1)Os(3), which are simultaneously bridged by OH and MeOCO ligands and a heterocyclic ligand is terminally coordinated to one of the two non-bonded osmium atoms. 相似文献