Downloaded 646 times
![ Those formed from the reagents yielding
large organic ions, eg.
Tetraphenylarsonium[(C6H5)4As+], which
tend to form large ionic clusters with
oppositely charged ions, like ReO4- . They
do not have a hydration shell & thus,
disrupt the water structure, due to which
the tend to be pushed into the organic
phase.
Those involving a cationic or anionic](https://image.slidesharecdn.com/solventauto-120107100631-phpapp01/85/SOLVENT-EXTRACTION-35-320.jpg)
Uploaded bySWAPNIL NIGAM
SOLVENT EXTRACTION
The document discusses various concepts related to liquid chromatography including: 1. Distribution ratio and separation factor which are important parameters in liquid-liquid extraction. 2. Different types of chromatography techniques like normal phase, reverse phase, adsorption, ion-exchange, size exclusion chromatography. 3. Key aspects of liquid chromatography instrumentation like the pump, injector, column, detectors, and data system. Common detectors discussed are UV-Vis, fluorescence, conductivity etc.
More Related Content
Similar to SOLVENT EXTRACTION
SOLVENT EXTRACTION
- 1.
- 8. thermodynamically rigorous
- 9. Distribution Ratio(D)”, Where, CA denotes concentration of „A‟ in all its form as determined analytically.
- 10. “Separation factor(or coefficient)”
- 12. For example, supposewe have Amount of solute in aqueous phase(xo)=300g Volume of aqueous phase = 100ml Volume of organic phase to be added = 200ml Distribution ratio of the particles = 0.5
- 13. NOW, The totalamount of solute (x n) left non- extracted in the aqueous phase („V‟ ml) on adding the extractive organic phase („v‟ ml) can be calculated using the formulae,
- 14. WHERE, xo = amount of solute present before adding extractive solvent D = Distribution ratio of the solute particles n = Number of times the solvent is added
- 15. CASE 1: If n=1, i.e., the extractive solvent is added in one complete go, then, from the formulae, we find that, x1 = 60g, that means 240g of the solute gets extracted. CASE 2: If n=2, i.e., if we add the extractive solvent in two parts each of 100 ml, then,
- 16. v=100ml, and usingthe formulae, we find x2 to be 33g, which implies that, 267g of the solute has been extracted.
- 17.
- 18. By formation of a neutral metal chelate complex, or By ion association.
- 19. INNER COMPLEXES
- 21. Basic strength of the chelating group Nature of the donor atoms of chelating agent
- 22. Size ofthe ring Resonance & steric effect
- 23.
- 24. The reagentand the metal complex exist as undissociated molecules in both phases. Solvation plays no significant part in the extraction process. The solutes are uncharged particle & their concentrations are so low that the solutions do not deviate much from ideality.
- 25.
- 26.
- 27. w w w
- 28.
- 29. o w w
- 30. o w * *
- 31. * w
- 32.
- 33.
- 34.
- 35. Those formedfrom the reagents yielding large organic ions, eg. Tetraphenylarsonium[(C6H5)4As+], which tend to form large ionic clusters with oppositely charged ions, like ReO4- . They do not have a hydration shell & thus, disrupt the water structure, due to which the tend to be pushed into the organic phase. Those involving a cationic or anionic
- 36. chelate complex ofthe metal ion. Thus, the chelating reagent consists of two uncharged donor atoms. Eg. 1:10 phenanthroline forms cationic complexes. Those in which solvent molecules are directly involved in the formation of ion- association complex. Eg. ethers, esters etc.
- 37. NAME FORMULAE REMARKS ACETYLACETO- CH3COCHCOCH3 PHENONE DIMETHYL- CH3COCHCOCH3 GLYOXIME
- 38. Partition Chromatography II Reverse Phase Chromatography – Nonpolar Stationary Phase – Polar Mobile Phase Normal Phase Chromatography – Polar Stationary Phase – Nonpolar Mobile Phase Column Selection Mobile-Phase Selection
- 39. Partition Chromatography III Research Applications – Parathion in Insecticides: O – CH3CH2O P O NO2 CH3CH2O – Cocaine in Fruit Flies: A Study of Neurotransmission by Prof. Jay Hirsh, UVa
- 41. Adsorption Chromatography Classic Solvent Selection Non-polar Isomeric Mixtures Advantages/ Disadvantages Applications
- 42. What is IonChromatography? Modern methods of separating and determining ions based on ion-exchange resins Mid 1970s Anion or cation mixtures readily resolved on HPLC column Applied to a variety of organic & biochemical systems including drugs, their metabolites, serums, food preservatives, vitamin mixtures, sugars, pharmaceutical preparations
- 43. The Mobile Phasesare... Aqueous solutions – containing methanol, water-miscible organic solvents – also contain ionic species, in the form of a buffer – solvent strength & selectivity are determined by kind and concentration of added ingredients – ions in this phase compete with analyte ions for the active site in the packing
- 44. Properties of theMobile Phase Must – dissolve the sample – have a strong solvent strength leads to reasonable retention times – interact with solutes in such a way as to lead to selectivity
- 45. Ion-Exchange Packings Typesof packings – pellicular bead packing • large (30-40 µm) nonporous, spherical, glass, polymer bead • coated with synthetic ion-exchange resin • sample capacity of these particles is less – coating porous microparticles of silica with a thin film of the exchanger • faster diffusion leads to enhanced efficiency
- 46. Ion-Exchange Equilibria Exchangeequilibria between ions in solution and ions on the surface of an insoluble, high molecular-weight solid Cation exchange resins – sulfonic acid group, carboxylic acid group Anion exchange resins – quaternary amine group, primary amine group CM Cellulose DEAE Cellulose Cation Exchanger Anion Exchanger
- 48. Eluent Suppressor Technique Made possible the conductometric detection of eluted ions. Introduction of a eluent suppressor column immediately following the ion-exchange column. Suppressor column – packed with a second ion-exchange resin Cation analysis Anion analysis
- 50. Size Exclusion Chromatography(SEC) Gelpermeation(GPC), gel filtration(GFC) chromatography Technique applicable to separation of high-molecular weight species Rapid determination of the molecular weight or molecular-weight distribution of larger polymers or natural products Solute and solvent molecules can diffuse into pores -- trapped and removed from the flow of the mobile phase
- 51. SEC(continued) Specific poresizes.average residence time in the pores depends on the effective size of the analyte molecules – larger molecules – smaller molecules – intermediate size molecules
- 52. SEC Column Packing Small (~10 µm) silica or polymer particles containing a network of uniform pores Two types (diameters of 5 ~ 10 µm) – Polymer beads – silica-based particles
- 53. Advantages of SizeExclusion Chromatography Short & well-defined separation times Narrow bands--> good sensitivity Freedom from sample loss, solutes do not interact with the stationary phase Absence of column deactivation brought about by interaction of solute with the packing
- 54. Disadvantages Only limitednumber of bands can be accommodated because the time scale of the chromatogram is short Inapplicability to samples of similar size, such as isomers. – At least 10% difference in molecular weight is required for reasonable resolution
- 56. Instrumentation Instruments required: – Mobile phase reservoir – Pump – Injector – Column – Detector – Data system
- 57.
- 58. Mobile phase reservoir Glass/stainless steel reservoir Removal of dissolved gases by degassers – vacuum pumping system – heating/stirring of solvents – sparging – vacuum filtration
- 59. Elution methods Isocraticelution – single solvent of constant composition Gradient elution – 2 or more solvents of differing polarity used
- 61. Pumping System I Provide a continuous constant flow of the solvent through the injector Requirements – pressure outputs up to 6000 psi – pulse-free output – flow rates ranging from .1-10 mL/min – flow control and flow reproducibility of .5% or better – corrosion-resistant components
- 62. Pumping System II Two types: – constant-pressure – constant-flow Reciprocating pumps – motor-driven piston – disadvantage: pulsed flow creates noise – advantages: small internal volume (35-400 L), high output pressures (up to 10,000 psi), ready adaptability to gradient elution, constant flow rates
- 63. Pumping System III Displacement pumps – syringe-like chambers activated by screw-driven mechanism powered by a stepper motor – advantages: output is pulse free – disadvantage: limited solvent capacity (~20 mL) and inconvenience when solvents need to be changed Flow control and programming system – computer-controlled devices – measure flow rate – increase/decrease speed of pump motor
- 64. Sample Injection Systems For injecting the solvent through the column Minimize possible flow disturbances Limiting factor in precision of liquid chromatographic measurement Volumes must be small .1-500 L Sampling loops – interchangeable loops (5-500 L at pressures up to 7000 psi)
- 66. LC column LC injector
- 67. Liquid Chromatographic Column Smooth-bore stainless steel or heavy-walled glass tubing Hundreds of packed columns differing in size and packing are available from manufacturers ($200- $500) Add columns together to increase length
- 68. Liquid Chromatographic Columns II Column thermostats – maintaining column temperatures constant to a few tenths degree centigrade – column heaters control column temperatures (from ambient to 150oC) – columns fitted with water jackets fed from a constant temperature bath
- 69. Detector Mostly optical Equipped with a flow cell Focus light beam at the center for maximum energy transmission Cell ensures that the separated bands do not widen
- 70. Some Properties ofDetector Adequate sensitivity Stability and reproducibility Wide linear dynamic range Short response time Minimum volume for reducing zone broadening
- 71. More Properties ofDetector High reliability and ease of use Similarity in response toward all analytes Selective response toward one or more classes of analytes Non-destructive
- 72. Types of Detector Refractive index UV/Visible Fluorescence Conductivity Evaporative light scattering Electrochemical
- 73. Refractive Index I Measure displacement of beam with respect to photosensitive surface of dectector
- 74. Refractive Index II Advantages – universal respond to nearly all solutes – reliable – unaffected by flow rate – low sensitive to dirt and air bubbles in the flow cell
- 75. Refractive Index III Disadvantages – expensive – highly temperature sensitive – moderate sensitivity – cannot be used with gradient elution
- 76. UV/Visible I Mercurylamp = 254nm = 250, 313, 334 and 365nm with filters Photocell measures absorbance Modern UV detector has filter wheels for rapidly switching filters; used for repetitive and quantitative analysis
- 77.
- 78. UV/Visible III Advantages – high sensitivity – small sample volume required – linearity over wide concentration ranges – can be used with gradient elution
- 79. UV/Visible IV Disadvantage – does not work with compounds that do not absorb light at this wavelength region
- 80. Fluorescence I Forcompounds having natural fluorescing capability Fluorescence observed by photoelectric detector Mercury or Xenon source with grating monochromator to isolate fluorescent radiation
- 81. Fluorescence II Advantages – extremely high sensitivity – high selectivity Disadvantage – may not yield linear response over wide range of concentrations
- 82. Conductivity Measure conductivityof column effluent Sample indicated by change in conductivity Best in ion-exchange chromatography Cell instability
- 83. Evaporative Light ScatteringI Nebulizer converts eluent into mist Evaporation of mobile phase leads to formation of fine analyte particles Particles passed through laser beam; scattered radiation detected at right angles by silicon photodiode Similar response for all nonvolatile solutes Good sensitivity
- 84.
- 85. Electrochemical I Basedon reduction or oxidation of the eluting compound at a suitable electrode and measurement of resulting current
- 86. Electrochemical II Advantages – high sensitivity – ease of use Disadvantages – mobile phase must be made conductive – mobile phase must be purified from oxygen, metal contamination, halides
- 87. Data System Forbetter accuracy and precision Routine analysis – pre-programmed computing integrator Data station/computer needed for higher control levels – add automation options – complex data becomes more feasible – software safeguard prevents misuse of data system
- 88. Electrophoresis…charged species migrate inelectric field Separation based on charge or mobility
- 89. Capillary electrophoresis higher voltagescan be used as the heat can be dissipated
- 90.