Chemical Separations

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Chemical Separations
Somsak Sirichai Lecturer
Semester 1/2002
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Lecturer Somsak Sirichai Office Chemistry
building, room c307 Phone [phone]
ext.3114 E-mail sirichai_at_bucc4.buu.ac.th Office
Hours Tuesday 8-10 am
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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 None

• Primary 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

a practical term used to describe the handling
of a sample before the measuring step

• spiking

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
lt80, modify the method.
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Separation Methods
separations involving

• phase changes

• extraction

• ion exchange resins

• chromatography

• electric field

• flotation

• membranes

• miscellaneous techniques

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Phase changes
sample
no vacuum applied
vacuum applied
solid to gas or vapor
solid to liquid
liquid to vapor
liquid to vapor
solid to vapor
Lyophilization
zone melting
volatilization
(vacuum, molecular, sublimation) distillation
(batch, azeotropic, extractive, steam,
immiscible solvents) distillation
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Extraction
sample
liquid
solid
liquid to liquid
Liquid to liquid countercurrent
liquid to solid
solid to liquid
solid to vapor
Supercritical fluid (SFE)
Batch, Continuous solvent heavier, Continuous
solvent lighter
SPE
Continuous (soxhlet)
countercurrent
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Ion exchange resins
sample
Neutral molecules
Ionic molecules
Ionic or polar molecules
Ion exchange Ion chromatography
Ligand Exchange
Ion retardation Ion exclusion
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Chromatography
column
flat
sample
Liquid mobile phase
gas mobile phase
Liquid mobile phase

• gas-liquid

gravity flow
pressure applied

• paper
• thin layer

• displacement
• multicolumn
• affinity

• size exclusion
• flash
• high performance

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Electric fields
sample
Ions deposited as metal
yes
no
electrodeposition
Gel type matrix required
yes
electrophoresis
no

• horizontal
• immunoelectrophoresis
• disc
• ion focusing

• Capillary zone
• electrophoresis
• Field flow
• fractionation

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Volatilization
the conversion of all or part of solid or a
liquid to a gas
The gas may be produced by
1. direct heating
2. applying the principle that strong acids
displace weaker acids and strong 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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Techniques
1. 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