Instrumentation & App of SFC by Laiq
- 1. Imran Laiq Roll No. 12 M.Sc. (Analytical Ch) Part II Semester III (2020-2021 ) CKT College New Panvel Date: 11/01/2021 Instrumentation and Application of SFC (Supercritical Fluid Chromatography) 1
- 2. Contents Introduction Critical properties of various solvents Instrumentation of SFC Solvent Delivery System Injectors Columns Restrictor Detectors Applications Use of SFC for Pharmaceutical References 2
- 3. Introduction SFC is a chromatographic technique in which the mobile phase is a supercritical fluid. The use of a supercritical fluid mobile phase in chromatography was first proposed in 1958 by J. Lovelock. A supercritical fluid is any substance at a temperature and pressure above its critical point. In the Supercritical region the substance is neither a gas nor a liquid, it is a fluid that has properties of both. Solubility in a supercritical fluid tends to increase with density of the fluid (at constant temperature). Since density increases with pressure, solubility tends to increase with pressure. At constant density, solubility will increase with temperature. 3
- 4. SF are obtained either by heating a gas above its critical temperature or by compressing a liquid at a higher pressure than its critical pressure . 4
- 5. Carbon dioxide pressure-temperature phase diagram 5
- 6. Solvent Molecular weight g/mol Critical temperature K Critical pressure MPa (atm) Critical density g/cm3 Carbon dioxide (CO2) 44.01 304.1 7.38 (72.8) 0.469 Water (H2O) 18.015 647.096 22.064 (217.755) 0.322 Methane (CH4) 16.04 190.4 4.60 (45.4) 0.162 Ethane (C2H6) 30.07 305.3 4.87 (48.1) 0.203 Propane (C3H8) 44.09 369.8 4.25 (41.9) 0.217 Ethylene (C2H4) 28.05 282.4 5.04 (49.7) 0.215 Propylene (C3H6) 42.08 364.9 4.60 (45.4) 0.232 Methanol (CH3OH) 32.04 512.6 8.09 (79.8) 0.272 Ethanol (C2H5OH) 46.07 513.9 6.14 (60.6) 0.276 Acetone (C3H6O) 58.08 508.1 4.70 (46.4) 0.278 Critical properties of various solvents Carbon Dioxide and water are the most commonly used supercritical fluids. The density of SF is 200 t0 400 times more than gaseous state, nearly its liquid state. 6
- 7. The SFC is generally consists of : • Solvent delivery system (Gas supply usually CO2 and Pump) • Injector • Oven • Column in a thermostat-controlled oven • Restrictor • Detector • Recorder/computer Instrumentation of SFC 7
- 8. Fig 2: Instrumentation of SFC with names of all parts 8
- 9. Solvent Delivery System Page 9 • Maintains precise mobile phase flow (1 to 10 L/min {OT} or 1 to 10 mL/min {Packed}). • Aids in the control of the system pressure (up to 60 Mpa). • Moves mobile phase in the liquid state under pressure through the injector into the column. Type of pump used in SFC is chosen based on column type: • 1- For packed column reciprocating pump is used • 2- For capillary column SF-syringe pump is used
- 10. Injectors a. Loop injection: is a direct transposition of what is applied in analytical SFC. A low pressure feed pump is used to fill the loop. This is mostly recommended for preliminary tests of column performance and elution parameters. 10
- 11. b. in-line injector: the system offers a better flexibility for changing the injected volume. A high-pressure pump is required to inject the feed solution, but the injected stream is dissolved in the eluent flow. C. in-column” injector: in this type mode is an alternative which permits injection of the feed solution directly onto the column, without any dilution. 11
- 12. Oven Page 12 A thermostated column oven is required for precise temperature control of the mobile phase. Conventional GC or LC ovensare generally used. Columns The column contains a highly viscous liquid (called a stationary phase) into which the analytes can be temporarily adsorbed and then released based on their chemical nature. This temporary retention causes some analytes to remain longer in the column and is what allows the separation of the mixture. Different types of stationary phases are available with varying compositions and polarities.
- 13. Types of analytical columns used in SFC Capillary columns are open tubular columns Packed columns • narrow internal diameter made of fused silica, with the stationary phase bonded to the wall of the column. • Smaller than GC capillary columns. • Typically 50 m in diameter, 10 to 20 mm in length. • Used for complex mixture. • More analysis time • Less sample capacity. • The columns are conventionally stainless steel. • Similar to HPLC columns (10, 5, or 3 m porous particles). • Typically 10 – 25 cm long X 4.6 mm in diameter. • Used for less complex mixture. • Shorter analysis time. • High sample capacity. 13
- 14. Restrictor or back pressure device Page 14 • It is used to maintain the desired pressure in column by controlled nozzle. • It keep mobile phase supercritical throughout separation and often must be heated to prevent clogging. • It is placed either the end of the column or after detector.
- 15. Detectors Page 15 However, the mobile phase composition, column type, and flow rate must be taken into account when the detector is selected.
- 17. In SFC the mobile phase is initially pumped as a liquid and is brought into the supercritical region by heating it above its supercritical temperature before it enters the analytical column. It passes through an injection valve where the sample is introduced into the supercritcal stream and then into the analytical column. It is maintained supercritical as it passes through the column and into the detector by a pressure restrictor placed either after the detector or at the end of the column. The restrictor is a vital component as it keeps the mobile phase supercritical throughout the separation and often must be heated to prevent colgging; both variable and fixed restrictors are available. Working 17
- 18. Applications SFC can be applied to compounds that are not separated by GC LC. Include species that are nonvolatile or thermally unstable and contain no chromophoric groups species. SFC is now commonly used for chiral compounds separations and purifications in the pharmaceutical industry and it has been applied to a wide variety of materials, including •Natural products •Drugs and Pharmaceuticals •Foods •Pesticides and herbicides •Surfactants •Polymers and polymer additives •Fossil fuels • Lipids • Carbohydrates • Industrial Chemicals • Metal Chelates and Organometallic Compounds • Enantiomers • Explosives and propellants 18
- 19. Use of SFC for Pharmaceutical • It has high separation efficiency. • Suitable for separation of isomers or structurally similar analytes. • The selectivity can be adjusted by varing several parameters like mobile phase, stationary, temperature, pressure, , etc. • It is fast( 3-5 times faster than LC, with reduced column equilibration time). • It is cost effective and generates less toxic waste than LC. 19
- 20. 1. Douglas A. Skoog, Donald M. West, F. James Holler, and Stanley Crouch Fundamentals of Analytical Chemistry - 9th Edition by CENGAGE pp 935-940 (2018). 2. Willard, Merritt, Dean, andd Settle. Instrumental Methods of Analysis, 7th edition, (1986). 3. Dar. Bashir Ahmed, Dar. Ayaz Mahmood Instrumental Methods of Chemical Analysis, 1st edition, Mamta publication (2020). 4. Larry M. Miller, J. David Pinkston, Larry T. Taylor Modern Supercritical Fluid Chromatography published Online by (ISBN:9781119626022). 5. Terry A. Berger SUPERCRITICAL FLUID CHROMATOGRAPHY by Agilent Technologies 2015. References 20
- 21. Acknowledgment I am thankful from all Teaching staffs of Department of Chemistry which helped me in completing my presentation work and special thanks from Dr. Manjiri Mahadadalkar ma’am for guiding me in organizing and preparing this project assignment. 21
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