含苯并呋喃环的聚苯基单醚喹噁啉

由含苯并呋喃环的芳族四酮与芳族四胺进行溶液缩聚反应，合成了两种新的含苯并呋喃环的聚苯基单醚喹啉，用红外光谱、元素分析、差热及热重分析对聚合物进行了表征，测试了力学性能，并对其在较低温度下形成的多孔薄膜进行了分离、透过性能的研究，实验结果表明，聚合物不仅具有优良的耐热性与力学性能，也具有良好的纯水透过率和截留性能．     

Application of artificial neural networks for gradient elution retention modelling in ion chromatography

Gradient elution in ion chromatography (IC) offers several advantages: total analysis time can be significantly reduced, overall resolution of a mixture can be increased, peak shape can be improved (less tailing) and effective sensitivity can be increased (because there is little variation in peak shape). More importantly, it provides the maximum resolution per time unit. The aim of this work was the development of a suitable artificial neural network (ANN) gradient elution retention model that can be used in a variety of applications for method development and retention modelling of inorganic anions in IC. Multilayer perceptron ANNs were used to model the retention behaviour of fluoride, chloride, nitrite, sulphate, bromide, nitrate and phosphate in relation to the starting time of gradient elution and the slope of the linear gradient elution curve. The advantage of the developed model is the application of an optimized two-phase training algorithm that enables the researcher to make use of the advantages of first- and second-order training algorithms in one training procedure. This results in better predictive ability, with less time required for the calculations. The number of hidden layer neurons and experimental data points used for the training set were optimized in terms of obtaining a precise and accurate retention model with respect to minimization of unnecessary experimentation and time needed for the calculation procedures. This study shows that developed, ANNs are the method of first choice for retention modelling of inorganic anions in IC.     

Modelling of retention behaviour of solutes in micellar liquid chromatography

In micellar liquid chromatography (MLC), the resolution for a given multi-component mixture can be optimized by changing several variables, such as the concentrations of surfactant and organic modifier, the pH and temperature. However, this advantage can only be fully exploited with the development of mathematical models that describe the retention and the separation mechanisms. Several reports have appeared recently on the possibilities of accurately predicting the solute retention in MLC. Although the retention and selectivity may strongly change with varying concentrations of surfactant, organic modifier and/or pH, the observed changes are very regular, and are well described by simple models. This characteristic enables a successful prediction of retention times and compensates the negative effect of the broad and tailed chromatographic peaks obtained for some solutes when micellar eluents are used. An overview of the models proposed in the literature to describe the retention behaviour in pure micellar eluents and micellar eluents containing an organic modifier, at a fixed pH or at varying pH, is given. The equations derived permit the evaluation of the strength of micelle-solute and stationary phase-solute interactions. The prediction of the retention based on molecular properties and the use of neural networks, together with the factors affecting the prediction capability of the models (linearization of the equations, dead time, critical micellar concentration, ionic strength and temperature) are commented on. The strategies used for the optimization of resolution are also given.     

Coupled HPLC-capillary GC – state of the art and outlook

HPLC fractions involving eluents of low to intermediate polarity can be introduced into capillary GC using the retention gap technique. Partial or complete solvent evaporation during sample introduction reduces the length of, or almost eliminates, the zone in the column inlet (retention gap) flooded by the introduced liquid, allowing introduction of larger HPLC fractions and/or use of shorter retention gaps. The corresponding techniques are reviewed. The retention gap technique is poorly suited for water-containing HPLC eluents (reversed phase HPLC) and fails completely if HPLC eluents contain, e.g., buffer salts. Various techniques for extracting such HPLC eluents are considered, preference being given to extraction into GC stationary phases from where solutes are thermally desorbed into the GC separation column. Limiting factors are diffusion of solutes within the liquid phase to be extracted and retention power of the extraction tubes.     

The chromatographic behaviour of cycloolefins on stationary phases of different polarity. Prediction of their retention indices and boiling points

Summary The retention indices of mono and polycycloolefins with endo or exo double bonds, on squalane or polypropylenglycol 425 are related to their physico-chemical properties such as boiling point, molar volume, molar refraction, and refractive index. Equations have been empirically obtained, from which accurate retention indices of these compounds can be predicted. Unknown boiling points of some of these compounds can also be calculated from their lineal relation with the retention index on squalane.     

Prediction of retention data from stationary phase constants in gas chromatography

Summary Specific retention volumes and retention indices for selected compounds can be predicted from different sets of stationary phase constants by multiple regression. Errors in the corresponding calculated retention times are between 5 and 15%. Intercept (A) and slope (B) values are given for 72 McReynolds stationary phases. The A value can be predicted from the retention index of benzene with a standard deviation of 9%.     

Retention behavior of polycyclic aromatic hydrocarbons in microcolumn liquid chromatography with acridine derivative as stationary phase

Retention behavior of polycyclic aromatic hydrocarbons (PAHs) on an acridine derivative stationary phase was examined in microcolumn liquid chromatography. 3,6-Bis(dimethylamino)-10-dodecylacridinium was electrostatically introduced into a cation-exchanger, and its selectivity was compared with that of octadecylsilyl-bonded silica gel. The former stationary phase provided smaller retention for non-planar PAHs than that achieved by the latter stationary phase. The results suggest that interaction between PAHs and the acridinyl ring dominates the retention of PAHs, and preferential retention of planar PAHs is attributed to the fact that they have more chance to interact with the acridinyl ring of the stationary phase than non-planar PAHs.     

Porous polymers coated with stationary phases Contribution of the support to retention behaviour in gas chromatography II. Chromosorb 101 and squalene; Chromosorb 101 and fractonitril VI

Summary Following previous work on the solue-stationary liquid phase-adsorben interaction phenomena associated with the use of active Chromosorb 101 support in gas chromatography, we have studied the retention of a series of different polarity compounds on columns of squalane and Fractonitril VI on Chromosorb P HMDS (an inactive support) and Chromosorb 101 (an active support). The experimental particion coefficients in these stationary phases and the adsorption constants on the Chromosorb 101 support have been calculated assuming that the partition and adsorption mechanisms are essentially independent.Principle author.     

Retention characteristics of a new butylimidazolium-based stationary phase

A new HPLC stationary phase has been synthesized based on the ionic liquid n-butylimidazolium bromide. Imidazolium was covalently immobilized on a silica substrate through an n-alkyl tether and the retention characteristics of the resulting stationary phase were evaluated systematically. Using 28 small aromatic test solutes and reversed phase conditions, the linear solvation energy relationship approach was successfully used to characterize this new phase. The retention characteristics of the test solutes show remarkable similarity with phenyl stationary phases, despite the presence of a positive charge on the new imidazolium phase. Operated in the reversed phase mode, this new stationary phase shows considerable promise for the separation of neutral solutes and points to the potential for a truly multi-modal stationary phase.