On the chromatography mechanism of reversed-phase liquid chromatography

Summary An equation is derived which can describe how the retention of solutes is influenced by the composition of the mobile phase in reversed-phase liquid chromatography, the retention of solutes in alkyl bonded stationary phase regarded as the complexation between solute molecule and the active sites on the surface of the stationary phase. When the stationary phase is not fully saturated by the organic modifier, the activity of the active sites, the activity coefficient of the adsorbed solute as well as the activity coefficient of the solute in the mobile phase depend on the composition of the mobile phase. However, when the stationary phase is fully saturated, the composition of the mobile phase mainly influences the activity coefficient of the solute in the mobile phase. In addition, the selectivity of retention is discussed in terms of the derived equation.     

Direct coupling of column chromatography and thin-layer chromatography

Summary A system has been developed by which a chromatographic column is directly coupled to a TLC plate. The column effluent is divided by means of a variable splitter, the smaller portion being used for automatic spotting on the start line of a thin-layer plate; the larger portion is collected in fraction tubes, as usual. Provisions have been made by which the positions of the TLC spots can easily be correlated with the corresponding fraction tubes. The apparatus may be left without attendance to operate overnight. Several examples are described.

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Direkte Kupplung von Säulen- und Dünnschicht-Chromatographie

Zusammenfassung Bei dem beschriebenen Verfahren wird die säule direkt mit einer DC-Platte gekoppelt, indem der Eluatstrom mit Hilfe eines variablen Teilers in zwei Ströme aufgeteilt wird. Der kleinere wird automatisch auf die Startlinie einer DC-Platte aufgetragen, während der größere Teilstrom wie gewöhnlich in Reagensgläsern eines Fraktionensammlers aufgefangen wird. Die Apparatur ermöglicht es, für jede Fraktion einen zugehörigen Fleck auf die Dünnschichtplatte aufzutragen. Man kann die Vorrichtung auch nachts ohne Überwachung arbeiten lassen. Mehrere Anwendungsbeispiele werden beschrieben.

     

On-line multidimensional chromatography using packed capillary liquid chromatography and capillary gas chromatography

The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix.     

生物大分子的混合模式色谱法——传统的色谱观点正在被改变

<正>有幸受邀为一个月前出版的J Chromatogr A撰写了一篇题为"生物大分子的混合色谱及应用"的综述文章,在此后又有几篇很有创意的相关论文发表,在此选择具有代表性的有关蛋白质和多肽分离的论文3篇及本人所撰写的综述文章共4篇论文的内容简要作一介绍。混合模式色谱(mixed-mode chromatography,MMC)指的是应用     

Reversed-phase liquid chromatography and argentation chromatography of the minor capsaicinoids

An investigation of the liquid chromatography of the minor capsaicinoids in a commercial capsaicinoid mixture is reported. Twelve stationary phases including C₈, C₁₈, C₃₀, phenyl, and cation-exchange chemistries were examined in combination with isocratic aqueous methanol and aqueous acetonitrile mobile phases. A phenyl stationary phase and aqueous acetonitrile mobile phase baseline-resolved 7 of 11 capsaicinoids, and selected ion chromatograms (LC–ESI-MS) demonstrated this was the most effective reversed-phase separation. Argentation chromatography with an alkyl or phenyl column and aqueous silver nitrate–methanol mobile phase revealed the presence of the 6-ene-8-methyl and 6-ene-9-methyl homocapsaicin isomers and the absence of 7-ene-9-methyl homocapsaicin. A mixed phenyl–cation-exchange stationary phase (charged with silver ion) enabled unique and useful separations of the capsaicinoids.     

Gas chromatography and high-performance liquid chromatography of natural steroids.

This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.     

Circulation chromatography

The main peculiarities and difficulties in the implementation of circulation chromatography are considered. The most impressive results obtained with the use of circulation liquid chromatography for the separation of isotopically substituted and isomeric organic compounds are given. The possibility of the preparative separation of the optical isomers of amino acid derivatives was demonstrated for the first time; thus, a new technique for the separation of optical isomers was developed. The capabilities of the circulation versions of gas-liquid and gas-adsorption chromatography are considered in detail. The possibility of the ultrafine separation of isotopically substituted compounds that differ by only one isotope atom, such as benzene and monodeuterobenzene, was demonstrated.     

Correlation chromatography

In correlation chromatography the usual chromatographic procedure is modified, utilizing the capabilities of microcomputers. The most striking property is the semicontinuous character of the method, leading to a very efficient use of the column and a rapid decrease in the detection limit in a relatively short time.     

Reversed-phase chromatography

HPLC (high-performance liquid chromatography) is an analytical method of great versatility and sensitivity. The use of silica-bonded non-polar stationary phases in place of the traditional polar stationary phases has resulted in the technique of reversed-phase chromatography. This has proved a most useful analytical tool, particularly for the analysis of biological samples. Furthermore the technique has great potential as a means of measuring a number of physicochemical properties.