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The three positional methoxy isomers, 3,4-di(p-bromophenyl)-1,2,5-triphenyl-cyclo-2,4-pentadien-1-methyl ether, 2,3-di(p-bromophenyl)-1,4,5-triphenylcyclo-2,4-pentadien-1-methyl ether, and 1,2-di(p-bromophenyl)-3,4,5-triphenylcyclo-2,4-pentadien-1-methyl ether (mol. wt. 634) were obtained during the course of synthesizing a compound suitable for obtaining a chemically bonded phase for high-performance liquid chromatography (HPLC). Attempts to separate these three isomers by open-column liquid chromatography failed and only partial separation is obtained with multiple-development thin-layer chromatography. A preparative column, 20 × 9.9 cm I.D., packed with 10-μm Lichrosorb SI-100 was successfully used. Structures were determined by mass spectrometry, nuclear magnetic resonance and elemental analysis. Equipment and technique for slurry packing preparative HPLC columns is described.

The requirements for the basic parts of liquid chromatographs are discussed briefly. These parts incude: a solvent reservoir, pumping systems, injection systems, column oven and columns, detectors, and recorders. A table listing the different models of the major suppliers is included. Photographs of the most popular models are shown. Major features of the different models are listed in the table.

The hardware requirements of gas chromatographs are reviewed briefly. A table listing major suppliers (alphabetically) and major models of each supplier is provided. The major features for each model are noted in the table.

The hardware requirements of gas chromatographs are reviewed briefly. A table listing major suppliers (alphabetically) and major models of each supplier is provided. The major features for each model are noted in the table.

A rapid and sensitive chromatographic method for determining the presence of the triterpenoid acids, β-boswellic acid and O-acetyl-β-boswellic acid, in very small amounts of resin is reported. The complete mass spectra for these compounds are presented. The authors also report for the first time the presence of these acids in Boswellia papyrifera.

The requirements for the basic parts of liquid chromatographs are discussed briefly. These parts include: a solvent reservoir, pumping systems, injection systems, column ovan and columns, detectors, recorders, and data modules. A table listing important features of different models from the major suppliers is included. Photographs of the various models are shown.

The requirements for the basic components of high-performance liquid chromatography systems are briefly discussed. The instrumentation described includes a solvent reservoir, pumping systems, injection systems, column ovens and columns, detectors, recorders, and data systems. Included is a table summarizing the key features of complete HPLC systems from major suppliers and photographs of many of the systems described in the table.

Parameters in micellar electrokinetic capillary chromatography were optimized for the separation of capsaicin, dihydrocapsaicin, and piperine: common pungent constituents in spicy foods. Chromatographic optimization involved manipulations with different buffer systems, capillary dimensions, applied potentials, organic modifier concentrations, and sample injection durations. Detection optimization involved the simultaneous electrochemical detection of the capsaicins on-line after the ultraviolet detection of piperine. In addition, a different cell design for end-column amperometric detection is introduced, using commercially available microelectrodes and a 25-μm i.d. column.

If the gas chromatographic retention behavior of a substance is measured under isothermal conditions at multiple temperatures, it is possible to predict, with good accuracy, the retention behavior under temperature-programmed conditions. Several methods for performing this prediction exist, but they are limited by lengthy calculations, limited applicability, or by assumptions that degrade accuracy. A consideration of the thermodynamic parameters affecting retention, along with carrier gas flow characteristics, leads to a simulation approach that is computationally feasible and accurate. Such a method is presented in this work, along with the results for some simulations. It is shown that retention in multiple-segment temperature programs may be predicted from isothermal data, with errors ranging from 0.1–10%, depending upon the quality of the input data, and the complexity of the temperature program.

The excess adsorption isotherms of methanol-water and acetonitrile-water mixtures are compared for C4, C8, and C18 types of reversed-phase adsorbents with the same type of silica support (Hypersil). Adsorption behavior of the organic modifier is also measured for three different types of C8 adsorbents (Bakerbond, Supelcosil, and Hypersil) and on the Ultracarb-ODS at different temperatures. It is shown that the adsorption behavior of acetonitrile for all types of bonded phases is similar, but that of methanol shows an obvious dependence on the alkyl chain length of the bonded phase.

The definition of dead volume in high-performance liquid chromatography and its determination on the basis of the thermodynamic Gibbs theory is discussed. The suggested thermodynamic approach can be applied to the description of any liquid chromatographic method such as normal phase, reversed phase, ion exchange, and even size exclusion. A method is suggested for the accurate calculation of the dead volume from mobile phase component disturbance peaks through the whole concentration range. The existence of negative values of capacity factors for some compounds is also explained.

Characterization of polystryene-divinylbenzene packing using low molecular weight compounds to determine mode and mechanism of separation in size exclusion chromatography (SEC) is described. Totally excluded and totally permeated molecular weights for four soft gels which differ only in percent crosslinking are determined. Tetrahydrofuran, pyridine, and chloroform were used as solvents. A large number of compounds, especially N-alkylated anilines, exhibited a non-size exclusion mechanism of separation. Exclusion limits for n-alkanes in pyridine were greater than in THF or CHCl3. Results with these soft gels were compared with data obtained on rigid gels. The application of this model study to the size exclusion chromatography of various solvent refined coal fractions is described.

The requirements for the basic parts of liquid chromatographs are discussed briefly. The instrumentation described includes a solvent reservoir, pumping systems, injection systems, column oven and columns, detectors, recorders, and data modules. A table listing important features of different models from the major suppliers is included. Photographs of the various models are shown.

The requirements for the basic parts of liquid chromatographs are discussed briefly. These parts include: a solvent reservoir, pump, injection system, column, detector and recorder. A table listing the different models of the major suppliers is included. Photographs of the most popular models are shown. Major features of the different models are listed in the table.