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SiliaSphere - Most Popular Bonded Phases

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In liquid chromatography, there are various modes of operation possible based on the interaction mechanism of the solute with the stationary phase (sorbent). Most known separation modes are summarized in the table below of which reversed-phase is the most popular one.

SiliaSphere Most Popular Bonded Phases
Mode
Normal (NP)
Reversed (RP) Ion Exchange (IEX)
Mode Mechanism
Polar or hydrophilic
Non-polar or lipophilic Ionic
Typical Stationary Phase
Bare silica or functionalized silica (Amine, Cyano or Diol)
Functionalized silica
(mostly C18, C8, C4,Cyano, Phenyl and PFP)
Ionic functionalized silica
(SAX, SCX) or polymer
Stationary Phase Polarity
Polar
Non-polar Anionic or cationic exchanger
Typical Mobile Phase
Non-polar organic solvents such as hexane, dichloromethane, THF
Mixtures of water or aqueous
buffers and organic solvents (mostly ACN, MeOH, THF). Ion pairing agents can also be added.
Water, buffers; acid; base
Stationary Phase Polarity
Non-polar
Polar Buffer or ionic

 

Typical Applications of Most Common Bonded Phases

Typical Applications of Most Common Bonded Phases
Sorbent Phase
Functional Group
Mode
Typical Applications
NP
RP
IEX
Silica - OH
    Most polar sorbent with a slight acidic character used for purification of non-polar and non-ionic compounds.
C18 - (CH2)17CH3
  Great start for method development. Presents the maximum retention of non-polar compounds. Usually used for peptides, pesticides, PCBs, PAHs, drugs, etc.
C8 - (CH2)7CH3
  Presents less retention compared to C18. Usually used for highly hydrophobic pesticides, small peptides and heavy drugs.
C4 - (CH2)3CH3
  Presents less retention compared to C18 and C8. Widely used for molecules with large hydrophilic regions such as peptides, proteines and zwitterions (in 300 Å).
C1 - (CH3)3  
  Lower retention compared to other reversed-phases used for for the purification of polar and non-polar pharmaceutical products, highly hydrophobic molecules.
Cyano (CN) -(CH2)2CN
  Normal: less polar sorbent compared to silica used for the purification of polar organic compounds.
Reversed: Moderate non-polar sorbent with less hydrophobicity than C18 or C8. Purification of cyclosporine and carbohydrates.
Phenyl (PHE) -C6H5  
  Moderate non-polar sorbent with different selectivity for aromatic compounds compared to other non-polar sorbents.
Pentafluorophenyl (PFP) -(CH2)3C6F5  
  For a new selectivity approach or the purification of conjugated compounds (isomers).
Amine (NH2) - (CH2)3NH2
 
Normal: polar sorbent with a basic character with less retention and a different selectivity for acidic/basic compounds compared to silica.
Ion Exchange: A weak anion exchanger with pKa of 9.8. At pH 7.8 or below, the functional groups are positively charged. It facilitates the rapid release of very strong anions such as sulfonic acids that may be retained irreversibly on SAX.
Diol - (CH2)3OCH2CH(OH)CH2OH
    Moderate polar sorbent with a neutral character used to extract polar compounds. Alternative to silica when acidic character is problematic.
Tosic Acid (SCX) - (CH2)2C6H4SO3H    
Due to the very low pKa (< 1), this silica is a strong cation exchangers. The most common use is likely for catch and release purification.
TMA Chloride (SAX) - (CH2)3N+(CH3)3Cl-    
The quaternary amine is permanently charged and commonly used for the extraction of weak cations that may not bind strongly enough to weaker anion exchangers.
TMA Acetate (SAX-2) - (CH2)3N+(CH3)3(CO2CH3)-    
The acetate counter ion is easier to exchange compared to the chloride ion. It is used for compounds with pKa < 5, such as carboxylic acids or to selectively purify acidic compounds or remove acidic impurities from reaction mixtures.

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