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143581
Chromatography
Description
Chemistry Mind Map on Chromatography, created by Crystal D'Souza on 05/07/2013.
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chemistry
chemistry
Mind Map by
Crystal D'Souza
, updated more than 1 year ago
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Created by
Crystal D'Souza
about 11 years ago
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Resource summary
Chromatography
All Methods have
Stationary Phase
Mobile Phase
Components can
Adsorb
The process of components in a solution being stopped from moving.
Desorb
The process of moving on after being adsorbed.
Thin Layer Chromatography (TLC)
Stationary phase
Thin powder spread on plate or glass
Mobile phase
Ethanol or Water
Techniques
A small spot of sample first placed onto end of the plate, higher that the solution depth - ORIGIN
The plate submerged in solution (solution BELOW the origin)
As solvent rises, the components in sample being tested separate
Identifying
Running standards (known samples) against the unknown sample
Calculating the Rf values
Compared to Paper
Faster
Detect smaller amounts
Better separation for less polar compounds
Corrosive materials can be used (eg. HCl)
Rf Values
Always be <1
Component most STRONGLY adsorbed with have LOWEST Rf value.
Rf = Distance moved from the origin by component/ Distance moved from origin by solvent
Column Chromatography
Phases
Stationary Phase
Solid or Solid thinly coated in viscous liquid, packed in a glass column
Mobile phase
Dripped in slowly from a reservoir above
Tap at the bottom allows the solvent (ELUENT) to leave at the SAME RATE it enters
High Performance Liquid Chromatography (HPLC)
Extremely Sensitive
Separate compounds RMM >1000
Differs from traditional chromatography
Solid particles - 10-20 x's smaller
small sample size better separation
Small particles = high resistance, so needs HIGH PRESSURE (14000 kPa)
Identification
In the ELUENT stream.
Passes through UV light (it absorbs UV light, and a reduced signal is picked up by detector)
Time taken to pass through is Retention Time (Rt)
Gas Chromatography (GC)
Features
Most sensitive
Detect tiny amounts ( 10^-12)
But compounds have to be
RMM < 300
Perfect for analysis of TRACE compounds
Two types
Gas - Liquid
Stationary - Liquid
Mobile - Gas (usually N)
Gas - Solid
Stationary - SOLID
Mobile - Gas (usually N)
Components repeatedly pass in and out of solution
Least soluble are swept out first
Most useful detector - flame ionisastion
Interpretation
Samples are injected at t=0
Each component forms one peak
Conc. of a compound can be determined by running standards
GC - Spiking with known can help compare to unknown sample
All methods can be combined together, along with Mass Spectroscopy
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