1 / 53

Supercritical fluid extraction (SFE) / Supercritical fluid chromatography (SFC)

Supercritical fluid extraction (SFE) / Supercritical fluid chromatography (SFC). Supercritical Fluid (SCF).

vea
Download Presentation

Supercritical fluid extraction (SFE) / Supercritical fluid chromatography (SFC)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Supercritical fluid extraction (SFE) / Supercritical fluid chromatography (SFC)

  2. Supercritical Fluid (SCF) At temperatures above Tc and pressures beyond Pc, substance exists as supercritical fluid , and not as gas or liquid. The SCF expands and contracts like gas and has solvent properties like liquid. Phase diagram for supercritical fluid

  3. Comparison of the properties of gas, Supercritical fluid and liquid SCFs are used as extraction solvents (e.g. extracting caffeine from coffee beans, fats from potato chips), carrier medium for chromatography, and solvents for disposal of organic hazardous wastes

  4. 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

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

  6. Physical Parameters of Selected Supercritical Fluids a Data taken from Refs. 62 and 63. B The density at 400 atm (p,,,,) end T, = 1.03 was calculated from compressibility data.” C measurements were made under saturated conditions if no pressure is specified or were performed at 25°C if no temperature is specified.

  7. Benefits of 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℃

  8. 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

  9. Phase diagrams for CO2 and H2O

  10. Supercritical Fluid extraction Supercritical Fluid chromatography Supercritical Fluid extraction (SFE) / chromatography (SFC) Components pump ( extraction cell)

  11. Commercial instruments Jasco SFC/SFE system (packed column)

  12. Oven Mixer Pre-heating coil Injector Stop valve Extraction vessel or column CO2 pump Liquid CO2 Cylinder Stop valve (optional) Cooling circulator Line switching valve Modifier pump Modifier Detector Back pressure regulator

  13. Pumps • Reciprocating pump • Syringe pump • Other pump modules

  14. Types of extraction cell Flow-through cell Headspace-sampling cell

  15. Columns • Open tubular capillary columns • Packed columns

  16. Restrictors • Fixed restrictors linear restrictor (fused-silica) tapered desire Integral restrictor ceramic frit restrictor metal restrictor (platinum, platinum-iridium or steel) • Variable restrictors variable nozzle (HP) backpressure regulator (BPR) (Jasco)

  17. linear restrictor tapered desire Integral restrictor ceramic frit restrictor Fixed restrictors

  18. Backpressure regulator Gap-adjustment screw Needle-driven solenoid Return spring Valve needle Needle seal Valve seat heater

  19. Detectors • UV detection • Fluorescence detection • Flame ionization detection • Electron capture detection • Mass spectrometric detection

  20. Characteristics of supercritical fluid extraction • Potential for reduced extraction times • Controllable extraction conditions • Potential for fractionation • Reduced risk of contamination • Compatibility with on-line methods of analysis (e.g. chromatography) • Flexibility with off-line analysis (e. g. spectrophotometry) • Possibility of class-selective extraction by appropriate choice of conditions

  21. Supercritical fluid extraction • Static extraction mode (steady state extraction) • Dynamic extraction mode (non-steady state extraction) • Recirculating mode

  22. Supercritical fluid extraction • Off-line • On-line SFE-GC SFE-LC SFE-MS SFE-SFC

  23. Off-line SFE

  24. pump heated tube four port valve extraction cell solvent vial modifier chamber Device for the preparation of modified supercritical fluid

  25. on-line SFE Cryotrapheater Schematic diagram of on-line SFE-SFC system a) CO2 cylinder b) pump c) extraction vessel d) cryotrapheater e) injection port f) chromatography column g) column oven h) detector i) transfer lines.

  26. Advantages of on-line SFE • Direct coupling of the analyte-containing supercritical fluid to a chromatographic separation system with appropriate detection • Eliminating sample handling after loading in the extraction cell Disadvantages of on-line SFE • Long periods of time • Understand the nature of analytes

  27. Directly coupled SFE-SFC • Dynamic focusing • Cryogenic focusing • Thermal modulator • Collection on a solid support • Static extraction

  28. SFE/SFC The direct connection of supercritical fluid extraction and supercritical fluid chromatography (SFE/SFC) has found many applications recently. SFE/SFC has the advantages of not requiring a concentrating procedure or a cleanup procedure before analysis. SFE/SFC is applied for various compounds from different matrixes, including caffeine extraction, tocopherol enrichment, flavors extraction and analysis of pesticide residues. The direct coupling of SFE with GC, GPC, etc. in an on-line approach is conceptually straightforward, assuming quantitative deposition of the extracted analyte into the chromatographic inlet. SFC-MS has found several useful applications in recent years. Three-dimensional chromatogram of the extract from the petroleum residue with supercritical carbon dioxide obtained by direct introduction into SFC [JASCO Corp].

  29. Recovery & solubility (a) Percentage recovery of atrazine from soil by SFE with carbon dioxide at different pressures after 15 min at 80℃ and constant flow rate (b) Calculated solubility at the same temperature

  30. Percentage extraction versus time of extraction ◆

  31. Modifiers for SFE/SFC

  32. The role of Modifier on SFE MeCN MeOH 1-propanol EtOH • Plots of modifier effects on efficiency for nonpolar solutes on C18 column at 80 oC and 210 bar, 2.0 mL/min. Solute: (A) naphthalene; (B) anthracene; Modifier: solid line with = methanol; broken line with = ethanol; dotted line with = 1-propanol; dashed line with = acetonitrile [Zou & Dorsey, 2000] ◆

  33. The parameters effect on solubility • The vapor pressure of the component • Interaction with the supercritical fluid ( Temperature, pressure, density and additives)

  34. Reduced solubility parameter Δ= δ1/δ2 δ1= 1.25 Pc1/2 [ρ/ρliq ] δ2＝(Δε/ Δν)1/2 δ2 : solubility parameter of solute Δε: the energy of vaporization at a given temperature Δν: the corresponding molar volume δ1 : solubility parameter of the fluid Pc : the critical pressure ρ : the density of the supercritical fluid ρliq: the density of the liquid gas

  35. Megastrol acetate Calculation of the solubility parameters, δ2 Group Δε (cal/mol) Δν (cm3/mol) 5*CH3 5(1125) 5(33.5) 6*CH2 6(1180) 6(16.1) 3*CH 3(820) 3(-1.0) 2*HC= 2(1030) 2(13.5) 3*C 3(350) 3(-19.0) 2*C= 2(1030) 2(-5.5) 2*C=O 2(4150) 2(10.8) OCO 4300 18.0 4 ring closure 5-6 atoms 4(250) 4(16.0) 2 conjugated double bonds 2(400) 2(2.2) 34735 328.1 δ2＝(Δε/ Δν)1/2= 10.29 cal1/2 cm-3/2

  36. Solubility in carbon dioxide at different temperature and pressures Anthracene Measured by the online FID method J . Chromatogr .A 785 (1997) 57–64

  37. Method development for SFE

  38. 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 compounds Can separate compounds beyond the volatility range of GC Compared to LC: Reduced analysis time

  39. Comparison of MW elution ranges for different types of column chromatography Source: Skoog, Holler, and Nieman, Principles of Instrumental Analysis, 5th edition, Saunders College Publishing.

  40. Advantages of supercritical fluid chromatography (SFC) • Applications in quality control and sample • Minimizes use of organic solvents • Detection down to ppb or μg (depending on choice of detector) • Non-destructive method for isolation or purification of compounds • Preparative separations

  41. Disadvantages of supercritical fluid chromatography • Limited chemical information (depending on detection system) • Complex samples can have low resolution

  42. Supercritical Fluid extraction Supercritical Fluid chromatography Supercritical Fluid extraction (SFE) / chromatography (SFC) Components pump ( extraction cell)

  43. The role of Modifier on SFC

  44. Different i.d. restrictors 160 atm 12 m m 160 atm 15 m m 160 atm 9 m m 6 m m 6 m m Chromatograms of enantiomers of -phenylethanol using different i.d. restrictors.(A) 6 m m, (B) 9 m m, (C )12 m m, (D) 15 m m.

  45. Effect of restrictor internal diameter on separation parameters

  46. SFC vs. HPLC: Resolution

  47. SFC: Speed and Resolution

  48. SFC vs. HPLC: Speed

  49. SFC: effect of Pressure P↗→ n↗→溶解度↗→tR↘

  50. Effects of temperature and pressure on retention factors J . Chromatogr .A 785 (1997) 57–64

More Related