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71.
High-speed liquid chromatography in the system silica gel/dry n-hexane and ultraviolet spectrometry have been used to study the composition of various types of commercially available mixtures of chlorinated biphenyls. Special attention has been paid to the analysis of highly chlorinated products. In addition to data previously published, retention times are recorded for 11 individual polychlorinated biphenyls. The results of high-speed liquid chromatography are compared with those obtained in several normal and reversed-phase thin-layer chromatographic systems.  相似文献   
72.
Individual state-to-state rotational transitions have been resolved in small angle scattering of polarized CsF molecules on Ne, Ar, C2, H6, N2, CO, CO2, CHF3 at center of mass energies of about 0.1 eV. The absolute inelastic cross sections range from 5Å2 up to 600Å2.  相似文献   
73.
The easily accessible 2,4-bis (4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide, LR, has been reacted with salts of N-protected amino acids 1 (Z-Gly-OH, Boc-Gly-OH, Boc-S-Ser(Bzl)-OH, Boc-S-Tyr(Bzl)-OH, Z-S-Arg(Z2)-OH, and Z-S-Pro-OH), at room temperature in CH2Cl2 to give the intermediates 2, mixed anhydrides. When 2 is treated with two moles of a base and one mole of the salt of an amino acid ester 3 (TosOH·H-Gly-OBzl, HCl·H-Gly-OBzl, HCl·H-Gly-OEt, and HCl·H-S-Phe-OtBu) at 0°C, the expected peptide 4 is isolated in high yields. LR is also found to be a useful reagent in a fragment coupling between Z-Gly-S-Ala-OH and TosOH·H-S-Leu-OBzl). This tripeptide was tested by means of HPLC (deprotection and amino acid analysis according to Izumiya was not necessary), and no epimerization (<0.7 %) was observed.  相似文献   
74.
Summary Copper(II) forms a stable colourless complex with thiourea. This property has been utilized to develop a Spectrophotometric method for the determination ofg quantities of thiourea. The complex absorbs in ultraviolet region and the determinations are carried out at 250 nm. The method permits the determination of thiourea from 10–60g with error not exceeding ± 1.0%.
Zusammenfassung Kupfer(II) bildet mit Thioharnstoff eine farblosa Komplexverbindung, die sich auf Grund ihrer Absorption bei 250 nm zur spektrophotometrischen Bestimmung von Mikrogrammengen Thioharnstoff eignet. 10 bis 60g Thioharnstoff lassen sieh mit einem Fehler von höchstens ± 1,0% bestimmen.
  相似文献   
75.
A method for the determination of geosmin and 2-methylisoborneol (MIB) in water by solid-phase microextraction (SPME) is presented. Various SPME fibre chemistries have been compared for their efficiency in extracting MIB from water. Extraction conditions including the extraction time and temperature have been optimised. A 30 ml water sample is extracted for 20 min at 60 degrees C using a divinylbenzene fibre, and the extract analysed by gas chromatography with ion-trap mass spectrometry detection. d5-Geosmin and d3-MIB are added as internal standards to compensate for any variability in the SPME process which is not carried out to equilibrium. Chemical ionisation, using acetonitrile as the reagent gas, was found to give superior sensitivity to electron impact ionisation (EI) for the detection of MIB. EI was used as the ionisation mode for detection of geosmin. The method shows good linearity over the concentration range 5-40 ng l-1 and gives detection limits of 1 ng l-1 for both geosmin and MIB. Recovery (93-110%) and precision (3-12%) over this concentration range, for both raw and treated drinking waters, are comparable to currently employed methods such as closed-loop stripping analysis (CLSA). The method offers the advantage of being simple to use, with much shorter analysis times in comparison to CLSA.  相似文献   
76.
Chemical Transport of FeP2 and FeP4 with Iodine Experiments on the chemical transport of FeP2 and FeP4 with iodine are discussed, considering the gaseous molecules I1, I2, FeI2, Fe2I4, FeI3, Fe2I6, PI3, P2I4, P4, P2, and P. Thermodynamic calculations give δH°(298) = 56.322 kcal and ΔS°(298) = 39.5 cal/K for the reaction FeP2,f + I2 = FeI2 + 0.5 P4 and δG°(923) = 35.8 kcal for the reaction FeP4,f + I2 = FeI2 + P4.  相似文献   
77.
A constrained cyclic ArgGly-Asp-D-Phe-Lys, abbreviated as cyclo(-RGDfK-), lipopeptide has been synthesized and incorporated into artificial membranes such as giant vesicles with DOPC and solid-supported lipid bilayers. The selective adhesion and spreading of endothelial cells of the human umbilical cord on solids functionalized by membranes with this RGD-lipopeptide have been observed. Furthermore, we have demonstrated strong selective adhesion of giant vesicles to endothelial cells through local adhesion domains by combined application of hydrodynamic flow field and reflection interference contrast microscopy (RICM). The adhesion can be inhibited by competition with a water-soluble RGD peptide. We suggest that this strategy could improve the efficiency of liposomes targeting used as vectors or as drug carriers to cells.  相似文献   
78.
C Scherer  U Wachter  S A Wudy 《The Analyst》1998,123(12):2661-2663
A method for the determination of testosterone in human hair by gas chromatography-mass spectrometry using d3-testosterone as internal standard is described. Our method consisted of alkaline digestion, fast liquid-liquid extraction, LH-20 chromatography and derivatization with heptafluorobutyric anhydride. Quantification was achieved by selected ion monitoring of m/z 680 (testosterone) and m/z 683 (d3-testosterone). Our method needed no complex corrections for isotope contributions. The procedure provided a sensitive and specific technique with good accuracy and precision. For the first time, testosterone has been quantified by gas chromatography-mass spectrometry in human hair. The concentrations (median, range, ng g-1 hair) reflected a significant (p = 0.05; t-test) sex difference with 2.7 ng g-1 (2.5-4.2) in male and 1.7 ng g-1 (1.0-3.4) in female hair.  相似文献   
79.
The Crystal and Molecular Structure of N,N′-Bis(trimethylsilyl) Oximidic Acid Bis (trimethylsilyl) Ester The X-ray structure analysis of the reaction product of oxalyl chloride with sodium bis(trimethylsilyl) amide formulated by PUMP and ROCHOW as N,N′-bis(trimethylsilyl) oximidic Acid bis (trimethylsilyl) ester shows that the suggested structure is correct for the solid state. The compound crystallizes in the space group P1 with a = 9.948(4), b = 6.612(3), c = 10.370(4) Å, α = 88.87(6), β = 116.95(4), γ = 98.23(6)°, and Z = 1. The molecule manifests symmetry 1 .  相似文献   
80.
Coexistence Relations, Preparation and Properties of Ternary Compounds in the System Cu/Mo/O The phase diagram of the ternary system Cu/Mo/O is presented at 773 K. The compounds CuMoO4, Cu3Mo2O9, Cu4Mo5O17, Cu6Mo5O18, Cu4–xMo3O12, and CuxMoO3 are found to be thermodynamical stable. The homogeneity range of Cu4–xMo3O12 runs to x = 0.1–0.2. Single crystals of CuMoO4 and Cu3Mo2O9 were grown by chemical transport reactions with TeCl4, Cl2, HCl, and Br2 as transport agent. The results were compared with thermochemical calculations. The decomposition of CuMoO4 and Cu3Mo2O9 was investigated with thermal analysis and decompositon pressure measurements.  相似文献   
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