|
High Aqueous Phases - Columns/pases compatible with 100% aqueous mobile phases
Introduction
AQ phases/columns are used to separating very polar, water-soluble compounds. Eluents containing less than 5% organic modifier are commonly used to achieve sufficient retention. However, operation under such highly aqueous conditions can lead to poor chromatographic reproducibility and decreasing retention times. Conventional C8 and C18 phases undergo 'phase collapse' under these conditions, resulting in a reduction of accessible bonded phase. This phenomenon may either occur very quickly or more gradually.
‘High Aqueous’ Phases
The phase collapse problem has been addressed by either embedding a polar group in the alkyl phase or by using hydrophilic (polar) endcapping reagents. . Both these approaches, or the use of a C30 phase, have the effect of maintaining the phase surface under fully wetted conditions, even when using 100% aqueous eluent.
AQ Phases show good retention and resolution for polar compounds
Compared to traditional alkyl phases these 'high aqueous' phases are resistant to retention loss when using highly aqueous eluents, even after several days or weeks. Reproducible retention times and improved peak shapes are achieved for acidic, basic and zwitterionic analytes.
Alternative selectivity
Conventional C18 phases depend predominantly on hydrophobic interactions between analyte and stationary phase to provide separation. In addition, ‘AQ’ type phases may also show hydrophilic (polar) interactions via H-bonding and dipole-dipole forces. This can influence retention time and improve selectivity for polar analytes.
Eliminate need for ion-pair additives
Many separations of very polar analytes are performed using ion-pair chromatography in order to provide adequate retention. The use of an ‘AQ’ phase generally enables reproducible results to be obtained using conventional aqueous/organic eluents.
Typical applications.
Typical applications of these ‘AQ’ type phases include carboxylic acids, water soluble vitamins, catecholamines, nucleic acid bases and various polar pharmaceuticals
‘High Aqueous’ Phases
|
Phase /Brand
|
Manufacturer
|
Particle Size (um)
|
Pore size (A)
|
Comments
|
|
ACE AQ
|
ACT
|
3, 5, 10
|
100
|
C18 with integral polar functionality
|
|
ACE C18 AR
|
ACT
|
3,5,10
|
100
|
C18 with phenyl moiety
|
|
ACE EXEL AQ
|
ACT
|
2,3,5,
|
100
|
UHPLC C18 material with integral polar functionality
|
|
AquaSep
|
ES Industries
|
3, 5
|
100
|
Embedded ether group
|
|
Capcell Pak C18 AQ
|
Shiseido
|
3, 5
|
120
|
C18 phase
|
|
Chromegabond ODS-PI
|
ES Industries
|
3, 5
|
120
|
Ureide embedded polar group
|
|
Cogent Bidenate C18
|
Cogent
|
4
|
|
Silicahydride
|
|
Cosmosil C18-PAQ
|
Nacalai Tesque
|
5
|
120
|
C18 phase with polymeric linkage
|
|
Develosil RPAQUEOUS
|
Nomura
|
3, 5
|
140
|
C30 ligands, monofunctional
|
|
Develosil RPAQUEOUS-AR
|
|
3, 5
|
140
|
C30 ligands, trifunctional
|
|
Epic Polar
|
ES Industries
|
3, 5, 10
|
120
|
Embedded ether group
|
|
Genesis AQ
|
Grace Davison
|
|
120
|
C18 phase
|
|
Hydrosphere
|
YMC
|
3, 5
|
120
|
Hydrophilic C18 surface
|
|
Hypersil GOLD aQ
|
Thermo Scientific
|
1.9, 3.5, 8, 12
|
175
|
Alkyl chain with polar endcapping
|
|
HyPURITY ADVANCE
|
Thermo Scientific
|
3, 5
|
190
|
Polar embedded C8 phase
|
|
HyPURITY AQUASTAR
|
Thermo Scientific
|
3, 5
|
190
|
Polar endcapped C18 phase
|
|
Inertsil ODS 4
|
GL Science
|
|
|
|
|
Inertsil ODS-EP
|
GL Sciences
|
5
|
100
|
C18 phase with polar embedded group
|
|
Inertsil SP
|
GL Science
|
|
|
|
|
MacroSep AQS
|
ES Industries
|
3, 5
|
300
|
Embedded ether group
|
|
NUCLEODUR C18 Pyramid
|
Macherey-Nagel
|
3, 5
|
110
|
C18 with hydrophilic endcapping
|
|
NUCLEOSIL Nautilus
|
Macherey-Nagel
|
3, 5
|
100
|
C18 with polar embedded group
|
|
Obelisc
|
SIELC
|
|
|
|
|
Primesep
|
SIELC
|
|
|
|
|
ProTec-RP
|
ES Industries
|
3, 5
|
100
|
C8, C18 or Phenyl with embedded amide group
|
|
Symmetry Shield
|
Waters
|
3.5, 5
|
100
|
C18 or C8 with embedded polar group
|
|
TSKgel ODS-100V
|
Tosoh Bioscience
|
3, 5
|
100
|
Difunctional C18 with difunctional endcapping
|
|
Ultisil AQ-C18
|
Welch Materials
|
3,5,10
|
120
|
|
|
YMC ODS-AQ
|
YMC
|
3, 5
|
120, 200
|
C18 with hydrophilic endcapping
|
|
Zorbax Bonus-RP
|
Agilent Technologies
|
3.5, 5
|
80
|
C14 chain with embedded amide group
|
|
Zorbax SB-Aq
|
Agilent Technologies
|
1.9, 3.5, 8, 12
|
80
|
Proprietary
|
|
Interesting Publications
AQ_Phases_HPLC_Analysis_of_Polar_Analytes_with_Aqueous_Mobile_Phases
AQ_Phases_Columns_for_RP_LC_Separation_in_Highly_Aqueous_Mobile_Phases
|
