Chromatography Information

java · Consumer

This is and interesting site as it has the output of many compounds, some are gas results others, liquid and gas chromatography results.....I sort of hacked it to get to the resource page ...the directions are in german but the compound name and results in english......java

java · Consumer

This is a brief defination of the different types of chromatography used in analyzing compounds.......souce encyclopaedia britannica
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Chromatography (kr?'m?t?g'r?f?) , resolution of a chemical mixture into its component compounds by passing it through a system that retards each compound to a varying degree; a system capable of accomplishing this is called a chromatograph. The retarding system can be a surface adsorbant, such as silica, alumina, cellulose, or charcoal, capable of reversibly adsorbing the compounds (see adsorption). The earliest use of this technique, by the Russian botanist Mikhail Tsvett (c.1903), involved the separation of highly colored compounds, hence the name chromatography [Gr.,=color recording].

Column Chromatography

In column chromatography the adsorbant is packed into a column and a solution of the mixture is added at the top. An appropriate solvent is passed through the column, washing, or eluting, the compounds down the column. A polar substance that is adsorbed very tightly to the surface will be efficiently retarded by the column, while a nonpolar substance will elute (dissolve in the solvent) very rapidly. By varying the nature of the solid adsorbant and the eluting solvent, a wide variety of resolutions, even of very similar substances, can be carried out.

Gas Chromatography

The gas chromatograph (GC) is a system consisting of a liquid with a high boiling point impregnated on an inert solid support as the stationary phase and helium gas as the mobile phase. The stationary phase is packed into a thin metal column and helium gas is allowed to flow through it. The column is attached to an injection port, and the entire system is heated in an oven. A solution of the mixture is injected into the column through the injection port by means of a syringe and is immediately volatilized. The helium gas then sweeps the components out of the column and past a detector. The polarity of the compounds and their volatility determines how long they are retained by the column. When each component passes the detector, a peak is registered on a recorder. The relative quantities of the components can be determined from the relative areas under the peaks. By varying the polarity of the column and its temperature, many different resolutions can be carried out. Since the capacity of GC columns is very low, the gas chromatograph is used chiefly as an analytical tool, although it can be used for preparative purposes as well. Miniaturized GC instruments have been employed in space probes to analyze the atmospheres of other planets.

Liquid Chromatography

For compounds that cannot be volatilized readily, the liquid chromatograph (LC) can be used instead of the gas chromatograph. The stationary phase consists of a finely powdered solid adsorbant packed into a thin metal column and the mobile phase consists of an eluting solvent forced through the column by a high-pressure pump. The mixture to be analyzed is injected into the column and monitored by a detector. Many different LC packings and eluting solvents are available to achieve the desired resolution.

Gel-Permeation Chromatography

In gel-permeation chromatography, compounds are separated on the basis of their molecular size. Porous beads of the gel are packed into a column and the mixture is added at the top in an appropriate solvent. Large molecules move straight down the column, while small molecules stick in the pores and are retarded.

Ion-Exchange Chromatography

For compounds that can exist as ions, ion-exchange chromatography can be used to separate them from neutral or oppositely charged compounds. The mixture is added to a column packed with a porous, insoluble resin which has a negatively charged (anionic) group attached to it and an unattached, positively charged (cationic) counterion. A cation from the mixture will exchange with the positive counterion of the resin and will be retarded while neutral and anionic substances are not affected. Ion-exchange resins with exchangeable anions work in a similar manner.

Thin-Layer and Paper Chromatography

A layer of adsorbant also can be spread on a glass plate, instead of packed into a column, for analytical purposes. By means of a thin capillary tube, the plate is spotted with a solution of the mixture that is to be resolved, and the solvent is allowed to evaporate. An eluting solvent is then allowed to move up the plate by capillary action, drawing the components of the mixture along by varying degrees. The plate is developed by spraying it with an oxidizing agent, so that each component becomes charred and appears as a dark spot on the plate. The location and size of the spots serve to identify and measure the relative quantities of the components. As in column chromatography, polar substances will not elute as well and will remain nearer the bottom of the plate, while nonpolar substances will elute to the top. This process is called thin-layer chromatography (TLC). In paper chromatography a procedure similar to TLC is used except that the cellulose in the paper acts as the adsorbant.

Electrophoresis

Electrophoresis, like ion-exchange chromatography, can be used as an effective tool for analyzing mixtures of ions. A strip of paper or a column of polymeric gel, saturated with an electrolyte, is set up so that it spans two solutions containing electrodes. The mixture to be analyzed is spotted onto the paper or gel and the two electrodes are connected to a high-energy power source (about 5,000 volts). Positive ions will migrate in one direction and negative ions in the other. The greater the charge on the ion, the farther it will migrate. This method is especially useful for the resolution of mixtures of proteins.

java · Consumer

Here is the link for TLC time , a thread from the hive dealing with TLC.....placed here to have some continuity...........java

java · Consumer

Here is a sticky file dealing with the topic of column chromatography.............java

methyl_ethyl · Riedel De Haen

Waters Corporation Liquid Chromatography and Mass Spectrometry Primers. Great source of basic principles and theory pertaining to LC and MS.

HPLC Primer

MS Primer

Guest · Wed Feb 23, 2005 3:06 am

Here is a place with virtual chemistry on some of the chromatography methods mentioned as well as spectography equipment.......watch and learn.....java

Lief · Thu Mar 03, 2005 8:39 am

Channel layer chromatography looks like it has some advantages.
http://v3.espacenet.com/pdfdocnav?DB=EPODOC&IDX=US3513092&F=128&QPN=US3513092

java · Consumer

A good review on GC and MS and what can obstruct from getting good results.......java

http://www.ionsigtech.com/introGCMS.htm

Excerp

An Introduction to Gas Chromatography/Mass Spectrometry

D. Ling, Ion Signature Technology

Gas Chromatography/Mass Spectrometry (GC/MS) is widely used to identify and quantify organic constituents that are thermally stable and have low boiling points. Liquid Chromatography/Mass Spectrometry (LC/MS) is used for those molecules that are thermally unstable and have high boiling points. Both techniques are used in a broad range of applications. MS is the only analytical technique that can provide unambiguous identification of organic compounds; it is the method of choice when the data generated must be able to withstand scrutiny in a court of law. MS can only provide this level of analysis when sample mixtures are simple or when sample components have been separated from each other. GC/MS is used more often than LC/MS since it provides much better separation efficiency and it is simpler to operate and maintain. GC/MS is commonly used in combinatorial chemistry analysis, petroleum analysis, forensic analysis, detection of illicit drugs, environmental risk assessments, etc. LC/MS is most often used to separate polar compounds such as pesticides, polymers, and proteins. Both instruments are used extensively as a research tools in industry, government, and academia, and for routine analysis in a broad range of applications.

left · Fri May 13, 2005 4:12 am

java · Consumer

http://www.lohninger.com/spectroscopy/dball.html
H. Lohninger
Spectral Data Bases and Interpretation Systems
Comprehensive Table of Spectroscopic Databases

Excerp
The table below contains an alphabetical list of spectroscopic databases for which information on the Internet is available. Such a list must be necessarily incomplete. If you know of some database which is not contained in this list, please send me the URL of it in order to include it.