Super critical fluid chromatography

intrumentation and applications of super critical fluid chromatography

1. SUPER CRITICAL FLUID CHROMATOGRAPHY DINESH K M PHARM PHARMACOLOGY 1

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3. CONTENTS Introduction Definition Principle Instrumentation Advantages Disadvantages Applications Conclusion References 3

4. WHAT IS SUPER CRITICAL FLUID? SCF can be described as a fluid obtained by heating above the critical temperature and compressing above the critical pressure. 4

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6. For every substance, there is a temperature above which it can no longer exist as a liquid, no matter how much pressure is applied. Likewise , there is a pressure above which the substance can no longer exist as a gas no matter how high the temperature is raised . These points are called critical temperature and critical pressure respectively. Above this point,the substance acts as a supercritical fluid . 6

7. A supercritical fluid is any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Additionally, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties to be "tuned ". Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. In the Supercritical region the substance is neither a gas nor a liquid – it is a fluid that has properties of both. There are no sharp boundaries between gas and liquid . 7

8. COMPARISON PROPERTIES OF GAS, SCF AND LIQUID. Property Gas (STP) SCF Liquid Density (g/cm 3 ) (0.6-2) x 10 -3 0.2-0.5 0.6-2 Diffusion coefficient (cm 2 /s) (1-4) x 10 -1 10 -3 x 10 - 4 (0.2-2) x 10 -5 Viscosity (G Cm -1 s -1 ) (1-4) x 10 - 4 (1-3) x 10 - 4 4 (0.2-3) x 10 -2 8

9. INTRODUCTION Supercritical fluid chromatography(SFC) was first proposed in 1958 by J. Lovelock . First used in1962 by Klesper . It is used for the analysis & purification of low moderate molecular weight, thermally liable molecules. 9

10. DEFINITION A supercritical fluid chromatography is a material that can be either liquid or gas used in state above critical temperature or critical pressure where gases or liquid can co exist. 10

11. PRINCIPLE Principles are similar to those of High Performance Liquid Chromatography (HPLC), however SFC typically utilizes carbon dioxide as the mobile phase; therefore the entire chromatographic flow path must be pressurized. Because the supercritical phase represents a state in which liquid and gas properties converge, supercritical fluid chromatography is sometimes called "convergence chromatography." 11

12. INSTRUMENTATION Stationary phase Mobile phase Pumps Injectors Restrictors Micropressure Ovens Columns Detector 12

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14. STATIONARY PHASE Both packed and open tubular columns are used . Packed columns can provide more theoretical plates and handle large volume than open tubular columns . Because of low viscosity of super critical media . The column length is 10 to 20m. and inside the diameter is 50 to 100mm common in open tubular columns. 14

15. CONT.. For difficult separation column 60m (or) large have been used . Packed column usually made up of stainless steel,10 to 25cm . More than 100,000 plates have been achieved in plate column . Many of column coating used in LC have been applied to SFC as well . Typically their are polysiloxane chemically bounded wall of capillary tubing . 15

16. MOBILE PHASE The mobile phase is composed primarily of super critical carbon dioxide, but since CO2 on its own is too non-polar to effectively elute many analytes , co-solvents are added to modify the mobile phase polarity. Co-solvents are typically simple alcohols like methanol, ethanol or isopropyl alcohol. Other solvents such as acetonitrile, chloroform or ethyl acetate can be used as modifiers. 16

17. CONTI.., Modify valves for analytes ,ethane, pentane, diethyl ether, ammonia.  Pressure maintained is 72.9 atm , temperature is 35ºc. 17

18. PUMPS Here mainly flow control is necessary so syringe pumps are used for capillary SFC for consistent pressure and for packed columns for easier blending of the mobile phase or introduction of modifier fluids reciprocating pumps are used . 18

19. INJECTORS In capillary SFC small sample should be quickly injected into the column and so pneumatically driven valves are used. For packed SFC a typical injection valve is commonly used. 19

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21. restrictors This is a device, which is used to maintain desired pressure in the column by a pressure-adjustable diaphragm or controlled nozzle so that the same column-outlet pressure is maintained irrespective of the mobile phase pump flow rate. It keeps the mobile phase supercritical throughout the separation and often must be heated to prevent clogging. The pressure restrictor is placed either after the detector or at the end of the column. 21

22. OVENS and micro processor Conventional GAS chromatography & liquid chromatography ovens are used . Microprocessor The commercial instruments for SFC are ordinarily equipped with one or more microprocessors to control such variables as pumping pressures, oven temperature and detector performance . 22

23. COLUMNS Two types of analytical columns are used in SFC packed and capillary. Packed columns contain small deactivated substances to which the stationary phase adheres. These are conventionally stainless steel. Capillary columns are open tubular columns made of fused silica which have small internal diameter. 23

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25. modifiers CO 2 is not a very good solvent for high molecular weight,ionic and polar analytes . This can be overcome by adding a small portion of a second fluid called modifier fluid. This is generally an organic solvent, which is completely miscible with carbon dioxide, methanol, acetonitrile, ethanol and 1-propanol. 25

26. DETECTORS Flame ionization detectors F lame photometry detector, liquid-phase detectors like refractive index detector , ultraviolet-visible spectrophotometric detectors light scattering detectors These types of detectors have been employed for SFC . 26

27. ADVANTAGES SFC is emerging as a separation technique that is superior to both gas chromatography and liquid chromatography for analysis of thermal liable or non volatile compounds. Low viscosity. Lower operating temperature. High diffusion co efficient. High resolution at low temperature. 27

28. DISADVANTAGES SFC is pressure operating conditions. High-pressure vessels are expensive and bulky. Maintaining pressure in SFC is difficult. supercritical fluids are highly compressible and their physical properties change with pressure. Cleaning will be time consuming. 28

29. APPLICATIONS SFC is used in industry primarily for separation of chiral molecules. SFC now commonly used for chiral separation and purification in the pharmaceutical industry. SFC technique has been applied to wide verity of materials , including natural products, drugs, food and polymers etc. 29

30. CONCLUSION In overall ranking of chromatographic techniques it can be judges that SFC falls somewhere between HPLC and GC. In field of pharmaceutical chemistry and bio analytical applications SFC gained its applications. 30

31. REFERENCES Muneo Saito (2008), [pdf Supercritical Fluid Chromatography : A New Technology ? ], Packed Column SFC 2008, Switzerland. Super critical fluid chromatography “ Skoog ” instrumental analysis pg : 935 to 940. Supplement and Cumulative Index, Edited by Bryant W . Rossiter and Roger C. Baetzold . Physical Methods of Chemistry Series, 2nd ed., Vol. X. ISBN 0-471-57086-9 0 1993 JohnWiley & Sons, Inc. 31

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