Super Critical Liquid Chromatography

8/2/2019 Super Critical Liquid Chromatography

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SUPER CRITICAL FLUIDCHROMATOGRAPHY

BY ABIJAH

08171S0417

MPAQA


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SUPER CRITICAL LIQUID

CHROMATOGRAPHY

Def

Introduction Principle

Instrumentation

Applications


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Definition

Chromatography: It is a method of separationof complex mixtures .

Super critical liquid chromatography: It is atype of column chromatography in whichsuper critical fluid is used as a mobile Phasefor the separation of mixtures.

Super critical fluid: A super critical fluid is thatwhich contains temperature and pressureabove its critical temperature and pressure.


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The critical temperature of a substance is the

temperature above which a distinct liquidphase cannot exist regardless of pressure.

The critical pressure is that the vapourpressure at its critical temperature.

No matter how much temperature andpressure is applied the substance cannotexists as a liquid.


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Introduction

This technique is a hybrid of Gas and Highperformance liquid chromatography.

It is relatively a recent chromatographic techniquewhich is commercially available since 1982.

Advantages such as rapid separation without the useof organic solvents, faster separation than HPLC,high resolution chromatography than GC therebyfaster analysis of thermo labile compounds.


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Super critical temperature and pressure are

the defining boundaries for a pure substance. Beyond these boundaries the properties of a

substances are intermediate between a liquidand gas.

In this region the fluid has a good solvatingpower and high diffusivity.


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Instrumentation


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An HPLC like setup with two reciprocating pumpsdesigned to provide a mixed mobile phase with a

packed analytical column placed in an oven followedby an optical detector in which the pressure and flowrates can be independently controlled .

A GC like setup with a syringe pump followed by a

capillary column in a GC oven with a restrictorfollowed by a flame ionization detector, where thepressure is controlled by the flow rate of the pump.


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In SFC the mobile phase is initially pumped as aliquid and is brought into the super critical region by

heating it above super critical temperature before itenters the analytical column.

It passes through an injection valve where the

sample is introduced into the super critical streamand then into the analytical column.


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It is maintained supercritical as it passesthrough the column and into the detector bya pressure restrictor placed either after thedetector or at the end of the column.

Restrictor prevents clogging

Mobile phase: Carbon dioxide, ethane,butane, nitrous oxide,dichlorodifluoromethane, diethyl ether,ammonia and tetrahydrofuran.


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Reciprocating pumps

Syringe pumps LC Injection valve (Pneumatically driven

valves)

Conventional GC or LC ovens

Capillary, stainless, Open tubular columns.

Stationary phase: Fused silica


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Detectors: Optical, Flame ionization detector,

Spectroscopic detectors. The results of a run in SFC are a

chromatogram.

Example: Chromatogram of separation of

polymers. It is schematically shown asfollows.


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Applications

Purification of thermo labile compounds.

Characterization of polymers. Complex distributions can be resolved, low

temperatures can be used

Oligomers can be detected.

Solute diffusivities

Separation of enantiomers


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Metabolites of estrogens are separated by

SFC . Separation of chiral and Achiral mixtures.

Natural products, drugs, foods, Pesticidesand herbicides, surfactants, fossil and

propellants.

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Super Critical Liquid Chromatography