SUPER CRITICAL FLUID CHROMATOGRAPHY

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SUPER CRITICAL FLUID CHROMATOGRAPHY:

SUPER CRITICAL FLUID CHROMATOGRAPHY gvrr416@gmail.com

CHARACTERISTICS:

CHARACTERISTICS It permits the separation and determination of compounds not separable by either HPLC or GLC. The temp above which a liquid phase cannot exist or a gas acannot be liquefied by an increase in pressure is the critical temp. The vapor pressure of a substance at its critical temp is called critical pressure. At a temp and pressure above its critical point a substance is called a super critical fluid.

COMPONENTS OF SFC:

COMPONENTS OF SFC gvrr416@gmail.com

COMPONENTS:

COMPONENTS PRESSURE REGULATOR Pressure variation affects an increase in density of the mobile phase which leads to an increase in solvent power of mobile phase and consequently the elution time. Pressure programming favors good separation of compounds. COLUMN AND STATIONARY PHASE Open tubular and closed columns used. Column of 10-20m length and 0.05-010mm i.d are used. MOBILE ELUTION PHASE Carbondioxide is commonly used mobile phase. It transmits UV, non toxic, odourless, cheap.Tc=31 °C and Pc=72.9 atms. DETECTORS Mostly FID, can be hyphenated with a mass spectrometer. gvrr416@gmail.com

COMPARISON OF SFC WITH HPLC AND GLC:

COMPARISON OF SFC WITH HPLC AND GLC Since properties of supercritical fluids are between gases and liquids, has the advantage of both HPLC and GLC. Low VISCOSITY of mobile ph- fast flow rate of gas. High diffusion density of fluid leads to greater band broadening. Faster separations with lower zone spreading. Better plate height(0.013mm) than liquids(0.039 mm) In SFC, the mobile phase not only transports the solvent but also interacts, thereby influencing selectivity factors.The molecule dissolves in fluid (similar to volatilisation in GLC).Thus partial pressure is higher for large molecules and so high molecular weight compounds can be easily eluted. Thermally unstable or large biological molecules can be easily eluted even at a low temperature.

APPLICATIONS:

APPLICATIONS Separation of Drugs, pesticides ,herbicides, fungicides and food products. Separation of a series of dimethyl polysiloxanes and oligomers. Since mobile phase is comparable with usual column chromatography with larger diffusion coefficients than in liquids, good speed of separation and rapid resolution. Separation of comp with M.W 400-700 daltons is possible with carbon dioxide as the m.p at a temp of 140 °C and pressure of 80 atms. Polycyclic aromatics and chlorinated hydrocarbons can be easily separated. Technique of derivation in GLC can be followed in SFC with all its advantages. Separation of oligomers in a sample of a nonionic surfactant like Triton X-100, with carbon dioxide as the m.p containing 1% methanol as the modifier. gvrr416@gmail.com

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