Separation behaviors of xylenol isomers by gas chromatography with helps of hydrogen bonding

Summary Xylenol isomers can be resolved on most polyols (sugars or sugar alcohols) and polyethers (polyethylene glycol or polypropylene glycol) with hydrogen-bonding interaction. They are separated on vinical polyols which have more hydroxy hydrogen than tetrol, and even on vicinal triol when its hydroxy hydrogen is acidic (stronger proton donor). The stronger is the hydrogen bonding interaction between xylenols and the liquid phase, the better is the separation of 2,4- and 2,5-xylenol, and the poorer the separation of 2,4-and 2,3-xylenol.     

The Chemical Constituents from the Aerial Part of Rosa laevigata

Eleven chemical constituents were isolated from the ethyl acetate soluble fraction of the aerial part of Rosa laevigata Michx. These compounds include the Henze's ketol (16), diethyl malate (17), three γ-lactones (18-20), loliolide (21), p-coumaric acid (22), 6,7-dimethoxycoumarin (23) and three flavonoids (24-26). The new compounds 19 and 20 were determined to be the cis- and trans-isomers of ethyl 2-benzyl-3-hydroxy-5-oxo-3-furancarboxylate.     

Conversions between ordered and disordered cellulose. Effects of mechanical treatment followed by cyclic wetting and drying

An investigation into the effects of mechanical treatment and hydration on the order of cellulose substrates (microcrystalline cellulose and Cladophora cellulose) was performed by the use of ball milling followed by cyclic wetting and drying. The results, monitored by¹³C-CP/MAS NMR-spectroscopy, were evaluated by calculation of the crystallinity indices and principal component analysis of the NMR data acquired. The results showed that a large part of the disorder induced by the mechanical treatment of cellulose by ball milling is reversible and reordering upon hydration leads to the cellulose I form initially present. The C4 signals corresponding to the reversibly disordered cellulose chains are observed in the amorphous region between 79 and 86 ppm in the¹³C-CP/MAS NMR-spectra together with signals from cellulose chains on the surface of ordered regions. The peak cluster which contains the C2, C3 and C5 ring carbons can be divided into two specific spectral regions; one between 74 and 77 ppm largely originates from ring carbons within disordered cellulose structures, and one between 70 and 74 ppm contains larger contributions from ordered cellulose. The behaviour of the celluloses upon milling is in accordance with a concept of ordered cellulose fibrils containing amorphous cellulose mainly as surface layers and induced reversible lattice distortions.     

三氟化硼引发四氢呋喃聚合的研究——Ⅳ.1,4-丁二醇的影响

前报中已证明用三氟化硼-环氧氯丙烷(ECH)引发四氢呋喃(THF)聚合具有较高的引发效率,并对在Ac_2O、水和无水存在下的聚合反应进行了研究。本文报道1,4-丁二醇(BG)对BF_3引发THF聚合反应的影响。通常认为在BG存在下,BF_3是不能引发THF聚合的,但本工作证明BG是有效的分子量调节剂,制备分子量在     

Characterization of Carbohydrates in Paper and Paper Pulps Using Anion Exchange Chromatography and Principal Component Analysis

In the course of this investigation, a method for the characterization and differentiation of paper pulps was developed. After hydrolyzation of the papers and the respective raw pulps with trifluoroacetic acid, the hydrolyzates were analyzed with respect to their carbohydrate composition using ion exchange chromatography. The variations in carbohydrate composition mainly arise from the various hemicelluloses of the papers and pulps. The chromatographic results were then further processed using principal component analysis which allows correlating the various papers to different pulp materials.     

中药微量元素的主成分分析

基于主成分分析的方法,研究了中药的相似性。主成分综合得分越近,中药就越相似。     

Phasentransferkatalysatoren auf Basis von Saccharose-Ethylenoxid-Addukten

Sucrose ethyleneoxide adducts have been prepared by reaction of sucrose with various amounts of ethyleneoxide inDMSO. The resulting polypode molecules were found to be efficient phase transfer catalysts in nucleophilic substitutions, oxidation and dichlorcarbene generation. Polymerisable polypodes have been obtained by reaction of sucrose ethyleneoxide adducts with methacrylic anhydride or methacryloylchloride in pyridine. Free radical polymerisation of the resulting mixtures of mono- and polyfunctional methacrylic esters of sucrose ethyleneoxide adducts yielded crosslinked gels. These polymer-supported octopus-molecules were found to be efficient triphase catalysts.

     

Stability of the FID sensitivity during an analysis in capillary GC

The sensitivity of an FID may change when the carrier gas flow rate changes during a chromatographic run. Sample parts which are eluted at reduced FID sensitivity produce a reduced peak area, hence are discriminated as compared to other components. Sensitivity changes were studied for hydrogen as carrier gas. For the detector tested, differences in the carrier gas flow rates of 1 ml/min shifted the FID sensitivity by 1 to 5% (depending on the fuel gas supply). Thus the stability of the sensitivity is no longer ensured as soon as the carrier gas flow rate is changed manually or by an automatic programmer during an analysis. Sensitivity drifts may also occur during temperature programmed runs with a pressure regulated carrier gas supply since the gas flow through the capillary drops with increasing temperature. Such shifts in the response became noticeable as soon as relatively high carrier gas flow rates combined with long range temperature programmes were used. The typical patterns of such discriminations are shown, closing with a discussion on the possibilities for minimizing such undesired effects.     

Crystal hydrates: an investigation of the use of crystal hydrates as stationary phases in gas chromatography

Summary The use of crystallohydrates, crystallohydrate solutions and melts as stationary phases in gas chromatography has been proposed. Crystallohydrates have been shown to display high selectivity in the separation of polar organic compounds when use is made of water vapours as the mobile phase. Some aspects of gas-liquid chromatography in water vapours and with the stationary phase comprising crystallohydrates have been studied, and the preliminary results obtained point to the desirability of further progress in this field.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Studies of the soluble part of oxidised coals

Soluble products obtained from the oxidation of four types of coal, each characterised by different degree of coalification and different degree of sulphur content, are studied. The coals are oxidised with peracetic acid (PAA) and nitric acid. Analyses are performed by Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) and Fourier Transform Infrared Spectroscopy (FTIR). The soluble products contain much more sulphur than the insoluble products of oxidation. The products obtained from the reaction with HNO₃ contain higher amounts of inorganic sulphur compounds, while those obtained from the reaction with PAA are characterised by an increased content of organic sulphur species.