GAS CHROMATOGRAPHY


   GAS CHROMATOGRAPHY

    INTRODUCTION

·         Separation technique
·         Discovered by Russian botanist- Mikhail Tswett in 1903.
·         Derived from Greek word- “chroma” and “graphein”.
·         Used in qualitative and quantitative analysis of molecules.
·         Two categories- (a) analytical (b)preparative
·         Partition or distribution coefficient Kd.
·         It is a process of separating components from the given sample by using a gaseous mobile phase.

Working principle

·         The sample solution injected into the instruments enters a gas stream which transports the sample into a separation tube known as the “column”.
·         The various components are separated inside the column.
·         The detector measures the quantity of the components that exit the column.

Instrumentation



Application

·         Analysis of foods like carbohydrates, proteins, lipids, vitamins, steroids, drug and pesticide residues, trace elements.
·         Pollutants like formaldehyde, carbon monoxide, benzene, DDT etc.
·         Dairy product analysis- rancidity
·         Separation and identification of volatile materials, plastics, natural and synthetic polymers, paints and microbiological samples.
·         Inorganic compound analysis.

     Advantages

·         This method has high sensitivity when used with thermal detectors
·         This technique gives relatively good accuracy and precision.
·         Separation and analysis of sample very quickly
·         Sample with less quantity is also separated.

       Disadvantages

·         Only volatile sample or those samples which can be made volatile are separated by this method.
·         During injection of the gaseous sample proper attention is required.
·         The sample of gas which is about to inject must be thermally stable so that it does not get degraded when heated.  

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