Transcript Adsorption/Partition Chromatography

Adsorption/Partition
Chromatography


Normal Phase
Reversed Phase
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Adsorption/Partition
Chromatography
Choosing mobile and stationary phases
 Stationary phase must have a similar polarity to the analyte
 Mobile phase is of substantially different polarity
Polarity Series
In general, polarity of organic compound in increasing order is:
Alkyl < alkenyl < aromatic < halides < sulfides < ethers < nitro <
esters ~ aldehydes ~ ketones < alcohols ~ amines < sulphones <
sulphoxides < amides < carboxylic acids < phosphates < water
Bold means that these groups can also be substantially affected by pH
changes
NB Avoid conditions that could decompose the analyte
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Normal Phase
Stationary phase:
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normally a solid
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Analyte adsorbs to the stationary phase

Packing is usually Silica or Alumina and
is therefore polar
Mobile phase:
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normally organic (i.e. not aqueous)
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wide choice of mobile phase
Retention:
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TR increases with polarity of analyte

Increasing the polarity of the mobile
phase reduces elution time

Optimisation normally consists of varying
the mobile phase
H3C
O
Si
Si
Si
Si
Si
H3C
H3C
O
Si
R
R
H3C
R=OH, CN, NH2 & more
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Reversed Phase
Stationary phase:
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normally a liquid
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Analyte dissolves in the stationary phase

Packing is usually modified Silica or
Alumina
Mobile phase:
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normally aqueous, plus MeOH orMeCN

wide choice of mobile phase buffers
Retention:

TR decreases with polarity of analyte

Increasing the polarity of the mobile
phase increases elution time

Optimisation normally consists of varying
the mobile phase
H3C
O
Si
Si
Si
Si
Si
H3C
H3C
O
Si
R
R
H3C
R= C18, C8, Ph & more
Created with MindGenius Business 2005®