Reversed phase HPLC columns have been widely used because of their superior resolution, high theoretical plate number and ease of use. Since hydrophobic interaction is the dominant separation mechanism in reversed phase chromatography, conventional stationary phases such as C₁₈ and C₁₈ do not offer optimum selectivity for compounds with similar hydrophobicity. COSMOSIL offers a broad selection of columns with unique stationary phases for separation of these difficult analytes. These columns offer improved separation of structurally similar compounds that are difficult to analyze with a C₁₈ type column.

Specifications

Packing Material	Cholester	PBr	πNAP	PYE	NPE
USP Code	L101
Silica Gel	High Purity Porous Spherical Silica
Particle Size	5 µm
Pore Size	approx. 120Å
Specific Surface Area	approx. 300 m2/g
Stationary Phase	Cholesteryl Group	Pentabromobenzyl group	Naphthylethyl Group	Pyrenylethyl Group	Nitrophenylethyl Group
Bonding Type	Monomeric
Main Interaction	Hydrophobic Interaction Molecular Shape Selectivity	Hydrophobic interaction Dispersion force	Hydrophobic Interaction π-π Interaction	Hydrophobic Interaction π-π Interaction Dispersion Force Charge-transfer Interaction	Hydrophobic Interaction π-π Interaction Dipole-dipole Interaction
End Capping Treatment	Near-perfect treatment
Carbon Content	approx. 20%	approx. 8%	approx. 11%	approx. 18%	approx. 9%
pH Range	2–7.5
Feature	Usable under the same conditions as C18 High molecular shape selectivity	Separate hydrophilic compounds in reversed phase conditions	Stronger π-π interaction than phenyl column	Strongest π-π interaction	Dipole-dipole interaction

Selectivity for positional isomers of dinitrobenzene

Different stationary phase exhibits different selectivity due to the use of forces that C18 (hydrophobic interaction) does not have. By using these columns, you can achieve separation that cannot be done using only C18.

Column Selection Guide

• COSMOSIL Cholester
• COSMOSIL PBr
• COSMOSIL πNAP
• COSMOSIL PYE
• COSMOSIL NPE