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PAPER CHROMATOGRAPHYPAPER CHROMATOGRAPHY SUBMITTED TO SUBMITTED TO Dr.K.M.LOKANATH RAI.sir Dr.P.NAGARAJ.sirDr.K.M.LOKANATH RAI.sir Dr.P.NAGARAJ.sir Dept.Of Chemistry Dept,Of Chemistry Manasagangothri Manasagangothri SUBMITTED BYSUBMITTED BY CHANDRAKANTHA.K.SCHANDRAKANTHA.K.S 2nd YEAR M.TECH.
Chromatography (from Greek :chroma, colour and "grafein" to write) is the collective term for a family of laboratory techniques for the separation of mixtures. It involves passing a mixture dissolved in a "mobile phase" through a stationary phase, which separates the analyte to be measured from other molecules in the mixture and allows it to be isolated.
Chromatography may be preparative or analytical. Preparative chromatography seeks to separate the components of a mixture for further use (and is thus a form of purification).
Mikhail Semyonovich Tsvet invented the first chromatographic technique in 1900 during his research on
chlorophyll. He used a liquid-adsorption column containing calcium carbonate to separate plant pigments.
In 1952 Archer John Porter Martin and Richard Laurence Millington Synge were awarded the Chemistry Nobel Prize for their invention of partition chromatography. Since then, the technology has advanced rapidly. This technique is a type of partition chromatography developed by CONSDEN,GORDEN,MARTAIN AND SRINGE IN ENGLAND IN 1944.
History
Is a technique used to separate and identify the components of a mixture.
Works by allowing the molecules present in the mixture to distribute themselves
between a stationary and a mobile medium.
Molecules that spend most of their time in the mobile phase are carried along faster.
Chromatography is a technique for separating mixtures into their components in order to analyze, identify, purify, and/or quantify the mixture or components.
Separate
• Analyze
• Identify
• Purify
• QuantifyComponentsMixture
Chromatography is used by scientists to:
• Analyze – examine a mixture, its components, and their relations to one another
• Identify – determine the identity of a mixture or components based on known components
• Purify – separate components in order to isolate one of interest for further study
• Quantify – determine the amount of the a mixture and/or the components present in the sample
On the basis of techniques employed in paper chromatography, it may be classified into 5 types.
Ascending paper chromatography
Descending paper chromatography
Ascending and descending paper chromatograpy
Radial or circular paper chromatography Two dimentional paper chromatography
Ascending paper chromatography: In this technique, the paper is supported vertically in a closed glass tank or tube. The lower edge of the filter paper sheet is dipped in suitable solvent known as eluting agent or developing agent. The mixture of components to be separated in solvent is spotted on filter paper strip. Since the lower end is dipped in solvent, the solvent rises up due to capillary action. Different ingredients of the mixture travel through different heights.
Descending paper chromatography: In this technique, the eluting agent is kept in a narrow trough near the top of the container. The upper end of the paper dips in it. In such case, the solvent move downwards. Then it is termed as descending paper chromatography. Descending chromatography is generally faster than the ascending method, but at the expense of a slight increase in complexicity of technique.
3. Ascending - Descending Chromatography: It is a hybrid of two techniques. The upper part of ascending chromatography can be folded over a glass rod allowing the descending development to change over into the descending after crossing the glass rod.
Radial or circular paper chromatography: In this technique, a circular piece of paper having a wick or tongue (of width of about 2 mm) cut parallel to the radius from edge of the centre is required. The mixture to be analysed is deposited as a spot at the centre of the paper which is upper end of the wick or tongue. After drying the spot, the paper is horizontally fixed on the petridish having the solvent so that the tongue of the paper dips into the solvent. The solvent flows through the tongue tough the paper. When the solvent front has moved through a sufficient large distance, the various components of the mixture are separated in the form of concentric circular zones or bands.
5. Two dimensional chromatography: In this a square rectangular paper is used. The sample applied on one of the corners. The second development is performed at right angle of the direction of first run. This type of chromatography can be carried out with identical solvent system in both directions or by two solvent systems
Sl.No Solvents used1 Isopropanol – ammonia - water (9 : 1 : 2)2 n-butanol - acetic acid – water (4 : 1 : 5)3 Water - phenol4 Formaldehyde - chloroform5 Formamide – chloroform - benzene6 Formamide - benzene7 Formamide – benzene - cyclohexane8 Dimethyl formamide – cyclohexane9 Kerosene - 70% isopropanol10 Paraffin oil – dimethyl formamide – methanol -
water
Common solvents used in paper chromatography
are as follows.
Common solvents used in paper chromatography
are as follows.
In the animation below the red molecules are more soluble in the liquid (or less volatile) than are the green molecules.
Retention The retention is a measure of the speed at which a substance moves in a chromatographic system. Retention is measured as the retention factor Rf, the run length of the compound divided by the run length of the eluent front:
The retention of a compound often differs considerably between experiments due to variations of the eluent, the stationary phase, temperature, sample matrix and the setup.
Retention The retention is a measure of the speed at which a substance moves in a chromatographic system. Retention is measured as the retention factor Rf, the run length of the compound divided by the run length of the eluent front:
The retention of a compound often differs considerably between experiments due to variations of the eluent, the stationary phase, temperature, sample matrix and the setup.
Rf = Distance moved by the compoundDistance moved by the solvent
ADVANTAGESIt can be used to determine the number of compounds in mixtureIt can be used to identify the specific compoundsIt can be used to monitor the process of reactionTLC has largely replaced by the paper chromatography
Several advantagesRun fasterBetter separationCan tolerate stronger solventsCan choose between different stationary phases
ConclusionsPaper chromatography one of the technique of
considerable importance.,but this is nolonger the case. still useful as an aid to teaching
chromatography in schools and colleges, there arevirtually no situations where separations originally
developed for paper chromatographic methods cannotnow be performed faster and better by TLC.