chemical separations
DESCRIPTION
3 0 3 4 5 1. Chemical Separations. Somsak Sirichai Lecturer. Semester 1/2002. Code : 303451. Subject : Chemical Separations . Credits : 2(2-0-4). Lecture : Chemistry building, room c310. Lecturer : Somsak Sirichai Office : Chemistry building, room c307 Phone : 038 745900 ext.3114 - PowerPoint PPT PresentationTRANSCRIPT
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Chemical Separations
303451
Somsak SirichaiLecturer
Semester 1/2002
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Lecturer: Somsak SirichaiOffice: Chemistry building, room c307Phone: 038 745900 ext.3114E-mail: [email protected]
Office Hours: Tuesday 8-10 am
Code: 303451Subject: Chemical Separations
Credits: 2(2-0-4)Lecture: Chemistry building, room c310
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Course Description: Study chemical separations. Topics: Volatilization, Distillation, Extraction, Ion Exchange, Chromatography and Electroseparation
Grading:Midterm exam 40%Final exam 40%Assignments 10%Quizzes 10%
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Text: NonePrimary References:• Karger, Snyder & Horvath; An Introduction to Separation Science• Meloan; Chemical Separations Principles, Techniques, and Experiments• Jönsson; Chromatographic Theory and Basic Principles• Ahuja; Trace and Ultratrace Analysis by HPLC• Khaledi; High Performance Capillary Electrophoresis
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What is separation?‘a process whereby the compounds of interest are removed from the other compounds in the sample that may react similarly and interfere with a quantitative determination’• important in the preparation of pure
compounds• often complex and may require several
different methods and much time before the final determinative step
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Terms common to chemical separations• cleanup
• spiking
a practical term used to describe the handling of a sample before the measuring step
the addition of a known amount of a standard to a sample so that recoveries can be determined and to calibrate the signal for quantitation
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Percent recovery:The amount of a spike that can be recovered when processed through the entire analysis procedure
values of 95-105% are desired.if <80%, modify the method.
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Separation Methods:
• phase changes• extraction
• ion exchange resins• chromatography• electric field• flotation
• membranes• miscellaneous techniques
separations involving
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Phase changes sample
no vacuum applied vacuum applied
solidto
gas or vapor
solidto
liquid
liquid to
vapor
liquid to
vapor
solid to
vapor
volatilization zonemelting
(batch, azeotropic, extractive, steam, immiscible solvents) distillation
(vacuum, molecular,sublimation) distillation
Lyophilization
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Extraction sample
liquid solid
liquidto
liquid
Liquid toliquid
countercurrent
liquid to
solid
solid to
liquid
solid to
vapor
Batch,Continuous solvent heavier,Continuous solvent lighter countercurrent
SPE Continuous(soxhlet)
Supercriticalfluid (SFE)
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Ion exchange resins
sample
Ionic molecules Ionic or polar
molecules
Neutral molecules
Ion exchangeIon chromatography
Ion retardationIon exclusion
Ligand Exchange
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Chromatography sample
Liquidmobile phase
gasmobile phase
Liquidmobile phase
column flat
gravity flow
pressure applied
• displacement• multicolumn• affinity
• size exclusion• flash• high performance
• gas-liquid
• paper• thin layer
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Electric fields sample
Ions deposited as metal
electrodeposition Gel type matrix required
yes no
electrophoresis• Capillary zone electrophoresis• Field flow fractionation
• horizontal• immunoelectrophoresis• disc• ion focusing
yesno
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Volatilization
‘the conversion of all or part of solid ora liquid to a gas’
The gas may be produced by:1. direct heating
2. applying the principle that strongacids displace weaker acids andstrong bases displace weaker bases
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Example:
• the evolution of CO2(g), weak acid, from solid CaCO3 by adding HCl,a strong acid
• the removal of NH3(g), a weak base, from solid (NH4)2SO4 by adding NaOH
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3. by oxidation• burning a sulfide in air to produce SO2
4. by reduction, or converting the elements to hydrides, such as AsH3, H2Se•
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Techniques1. Moisture determination
Fig. Microwave oven for drying food
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2. Determination of Mercury in the Environment by Volatilization
Fig. Apparatus for flameless AAS
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Next lecture:
Distillation