芳香族共聚酯液晶的椭圆偏振光谱与光学性质的研究

应用自动化椭圆偏振光谱和紫外－可见光谱表征了两种芳香族共聚酯液晶的光学性质，发现由于分子结构和受激发电子振动跃迁的不同，使共聚酯液晶薄膜具有不同的折射率变化，产生不的同光学色散现象。     

The mass detector: A new detection system for carbohydrate and lipid analyses

Summary The mass detector was investigated as an alternative to RI detection for carbohydrate and lipid analyses with high pressure liquid chromatography. The instrument was found to be more sensitive than most RI detectors and, as gradient elution could also be carried out, the resulting chromatograms showed improved resolution.     

Ground state of liquid helium-3: off-shell effects due to non-local potentials

It is shown that by incorporating the off-shell effects through the introduction of phase equivalent nonlocal potentials, (that are essentially equivalent so far as two-body properties are concerned) one could obtain a much better agreement regarding the important properties of the ground state of liquid helium-3, in lowest order Brueckner-Goldstone theory. The binding energy, equilibruim density and the convergence character of Brueckner-Goldstone series improve drastically.     

Gas-chromatographic separation of underivatized steroids using a BPhBT liquid crystal stationary phase

A gas-chromatographic separation of underivatized steroids is described, in which the liquid crystal N,?-bis(p-phenylbenzylidene)α,α′-bi-p-toluidine (BPhBT) was used isothermally at 265°C for the stationary phase. The nematic range of this crystal is 247 to 403°C. Use of the BPhBT crystal allowed operations in a temperature range where steroids are volatile and unlikely to display broad elution peaks and long retention times. With columns precoated with 2.5 weight percent of BPhBT, steroids containing minor structural differences in the ring system were readily differentiated. For example, 5-androsten-17α-ethinyl-3β, 17β-diol was found to elute more rapidly than its 3-keto analog, ethisterone. Ethisterone was distinguished readily also from its 19-nor analog, norethisterone. Additionally, differences in side-chain functionality and resultant molecular dimensions facilitated the separation of steroids of identical ring structure, as in the comparison of cholesterol with methyl 3β-hydroxy-5-cholenate and 25-hydroxycholesterol. An enhancement of separation according to the molecular length-to-breadth ratio was observed; in general, the larger this length-to-breadth ratio, the greater the retention period on the column.     

Computer investigation of physical properties of water clusters. 1. Stability

The method of molecular dynamics is applied to investigate the stability of water clusters containing up to 90 molecules. With increasing size of aggregates, (H₂O)_n≥10 10, their thermal stability strengthens. Mechanical stability of great clusters keeps the quickly reached level, and the coefficient of dielectric stability passes through the maximum at n = 50.     

Two-dimensional classification of amphiphilic monomers based on interfacial and partitioning properties. 1. Monomers of synthetic water-soluble polymers

A classification of amphiphilic monomers based on the interfacial and partitioning properties has been proposed. Monomers partitioned at equilibrium between two immiscible phases were ascribed with a pair of parameters: standard free energy of adsorption at the interface and standard free energy of partition between the two phases. These two parameters are represented in a form of two-dimensional diagram (both of them being normalized by kT factor). Comparison of the parameters in question gives information on energetic preferences of the molecules to be located at the interface or in the bulk phases. Four monomers of synthetic water-soluble polymers, namely, N-isopropylacrylamide, 1-vinylimidazole, N-vinylpyrrolidone and N-vinylcaprolactam have been classified according to the above method at various temperatures. The possibility to extend the classification to arbitrary chemicals is discussed.An erratum to this article can be found at     

Operational variables of size exclusion columns with semirigid and rigid packings

Systematic studies on operation variables affecting GPC separations using the semirigid Microstyragel (Waters Associates) and the rigid silica packings (DuPont) of about equivalent porosity are reported. The dependence of (a) flow rate, (b) injection volume, and (c) concentration on elution volume and theoretical plates are examined.     

Determination of the reactive surface area of silica

Summary The surface area available for reaction in silylation reactions has been determined by reaction of the silica with a radioactively labelled alkyldimethylchlorosilane followed by liquid scintillation counting of either a solid or a dissolved silica sample. The results are compared with values obtained by nitrogen adsorption and the pore size distributions of the products before and after reaction.Presented at the 14th International Symposium on Chromatography London, September, 1982     

An HPLC fluorescence detection system for amines

A detection system is described which is based on fluorescent ion-pair formation between tertiary amine drugs and dimethoxyanthracene sulphonate. A dynamic micro-extraction principle is then used to isolate the ion-pairs from the excess reagent. The band broadening of this extraction detector was kept below 20% using standard auto-analyser equipment. With the enhanced selectivity and sensitivity of this approach it was possible to analyse chloropheniramine in urine at ppb concentrations using a pre-column clean-up trace enrichment step.