Super critical fluid chromatography

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Prepared & presented by:- Shraddha Patel Mpharm 1st SEM (QA) Roll no: 16 Guided by:- Dr. Nehal.J.Shah Dharmaj Degree Pharmacy College Dharmaj :

Prepared & presented by:- Shraddha Patel Mpharm 1st SEM (QA) Roll no: 16 Guided by:- Dr. Nehal.J.Shah Dharmaj Degree Pharmacy College Dharmaj Supercritical Fluid Chromatography

CONTENTS::

CONTENTS: Introduction Properties of Supercritical Fluids Instrumentation:- Applications :-

Introduction:

Introduction Supercritical fluid chromatography (SFC) is a hybrid of gas and liquid chromatography that combines some of the best features of each. Supercritical fluid chromatography is of importance because it permits the separation and determination of a group of compounds that are not conveniently handled by either gas liquid or liquid chromatography.

Definition:

Definition A supercritical fluid is a material which can be either liquid or gas, used in state above the critical temperature and critical pressure where gases and liquid can coexist. Supercritical fluid have a viscosity close to gases, a density close liquids and a high diffusivity.

Properties of Supercritical Fluids:

Properties of Supercritical Fluids The critical temperature is the temperature above which a distinct liquid phase cannot exist, regardless of pressure. The vapor pressure of a substance at its critical temperature is its critical pressure. Carbon dioxide is known to be the most stable and an excellent solvent compound and is normally used in mobile phases for supercritical fluid chromatography.

Supercritical Fluid (SCF):

Supercritical Fluid (SCF) At temperatures above T c and pressures beyond P c , substance exists as supercritical fluid , and not as gas or liquid. The SCF expands and contracts like gas and has solvent properties like liquid.

Advantages of Supercritical Fluids:

Advantages of Supercritical Fluids lower operating temperatures improved yield improved product properties favorable combination of process steps easier regeneration of the SC solvent lower production cost solvent power comparable to liquid solvents very high volatility compared to the dissolved substances complete separation of solvent from extract and raffinate

Disadvantages of Supercritical Fluids:

Disadvantages of Supercritical Fluids elevated pressures required relative high costs of investment unusual operating conditions complicated phase behavior

Slide 9:

SFC characteristics : Faster linear velocity than LC Greater separation efficiency per unit time than LC Greater solute solubility than GC Greater mobile phase selectivity than GC Advantages compared to LC or GC : Compared to GC: Can separate thermally unstable compoundsCan separate compounds beyond the volatility range of GC Compared to LC: Reduced analysis time

Instruments and Operating Variables:

Instruments and Operating Variables The pressures and temperatures required for creating supercritical fluids lie within the operating limits of ordinary HPLC equipment. Thus, as shown in the figure next, instruments for SPC are similar in most regards to the instruments for HPLC.

Apparatus:

Apparatus

Effects of Pressure:

Effects of Pressure Pressure changes in supercritical chromatography have a pronounced effect on the capacity factor k’. This effect is a consequence of the increase in density of mobile phase with increase in density of the mobile phase with increases in pressure.

Stationary Phases:

Stationary Phases Both open-tubular and packed columns are used for SFC although currently the former are favored. Open-tubular columns are similar to the fused-silica columns with internal coatings of bonded and crossed-linked siloxanes of various types.

Mobile Phases:

Mobile Phases The most widely used mobile phase for SPC is carbon dioxide. It is an excellent solvent for a variety of organic molecules. In addition, it transmits in the ultraviolet and is odorless, nontoxic, readily available, and remarkably inexpensive when compared with other chromatographic mobile phases.

supercritical carbon dioxide:

supercritical carbon dioxide Moderate critical pressure (73.8 bar) Low critical temperature (31.1℃) Low toxicity and reactivity High purity at low cost Useful for extractions at temperature < 150℃

Benefits of supercritical carbon dioxide Ctd.:

Benefits of supercritical carbon dioxide Ctd . Ideal for extraction of thermally labile compounds Ideal extractant for non-polar species, e. g. alkanes Reasonably good for moderately polar species, e. g. PAHs Can directly vent to atmosphere Little opportunity for chemical change in absence of light and oxygen Gas at room temperature, allows for coupling to gas chromatography and SFC

Detectors:

Detectors A major advantage of SFC over HPLC is that the flame ionization detector of gas chromatography can be employed. Mass spectrometers are also more easily adapted as detectors for SFC than HPLC.

Applications of SFC Separations:

Applications of SFC Separations Qualitative and Quantitative Fractionation of complex mixtures Nondestructive, separation of closely related compounds Samples Environmental sensing Monitoring pesticides and insecticides Purification of complex mixtures Surfactants and hydrocsarbons Active drugs, synthetic byproducts, and degradation products

Slide 19:

Separation of polymers and polymer additives Determination of molecular weight distribution Limitations Sensitivity and detection limits dependent on the type of detector used Resolution is difficult for complex mixtures

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