What is the Difference Between C8 and C18 Column?

The main difference between C8 and C18 columns lies in the polarity and hydrophobicity of their bonded phases. Both C8 and C18 are reversed-phase columns used for analyzing weakly polar substances. Here are the key differences between the two:

1. Bonded Phases: C8 columns have octadecyl (C18) groups bonded to the silica support, with 18 carbon atoms in each group. C8 columns have octyl (C8) groups bonded to the silica support, with 8 carbon atoms in each group.
2. Polarity: The polarity of C18 is smaller than that of C8. C8 is on the side with stronger polarity, while C18 is on the side with weaker polarity.
3. Hydrophobicity: C8 columns are less hydrophobic than C18 columns. The longer the carbon chain, the more hydrophobic the stationary phase.
4. Applications: C18 columns are suitable for acidic, basic, neutral, polar, medium polar, and non-polar sample analysis. C8 columns are suitable for lipids, steroids, analytes with high hydrophobicity, and samples with different hydrophobicity.

In summary, C18 columns have a weaker polarity and are more hydrophobic than C8 columns. They are suitable for a wider range of analytes, while C8 columns are specifically useful for hydrophobic samples and compounds with high hydrophobicity.

Comparative Table: C8 vs C18 Column

The main difference between C8 and C18 columns lies in the stationary phase and the polarity of the alkyl chain. Both C8 and C18 columns are reversed-phase columns used in high-performance liquid chromatography (HPLC) systems. Here is a comparison between the two columns:

C8 columns have Octylsilane as the stationary phase, with 8 carbon atoms in the alkyl chain, while C18 columns have Octadecylsilane as the stationary phase, with 18 carbon atoms in the alkyl chain. The C18 column has a smaller polarity than the C8 column. This difference in polarity leads to C18 columns having a stronger analyte retention performance than C8 columns. Additionally, the higher carbon content in the C18 column results in a longer retention time for the main components. In general, C18 columns are more suitable for separating compounds with stronger hydrophobic interactions.