What is the Difference Between C18 and Phenyl Column

The key difference between C18 and phenyl columns is that the separation given by the C18 HPLC columns is lower compared to that of phenyl HPLC columns.

C18 column in HPLC is a column that uses a C18 substance as the stationary phase, while the phenyl column is a type of column that can be found in some HPLC instruments. It has short alkyl phenyl ligands that are covalently bound to the silica surface.

CONTENTS

1. Overview and Key Difference
2. What is a C18 Column
3. What is a Phenyl Column
4. C18 vs Phenyl Column in Tabular Form
6. Summary – C18 vs Phenyl Column

What is a C18 Column?

A C18 column in HPLC is a column that uses a C18 substance as the stationary phase. Therefore, these are known as C18 HPLC columns. These are useful in environmental sciences and chemical analysis. Furthermore, C18 HPLC columns are important in the pharmaceutical industry and environmental sciences for the analysis of individual parts of chemical mixtures.

Figure 01: A Typical HPLC Column

Typically, these C18 columns use octaldecylsilane, and this substance contains 18 carbon atoms that are bound to silica. This means this compound has more carbon atoms and a longer carbon chain than C-8. The extra carbon atoms in these carbon chains make a large surface area for the mobile phase to travel across.

Generally, we can use a C18 column in HPLC as a reverse-phase column. This is because this type of column uses more polar solvents (e.g. water, methanol, and acetonitrile). In addition, the stationary phase is a nonpolar hydrocarbon (C18).

What is a Phenyl Column?

A phenyl column is a type of column that can be found in some HPLC instruments that have short alkyl phenyl ligands covalently bound to the silica surface. However, in modern HPLC columns, we can find diphenyl phases that are developed to enhance pi-pi interaction. There is a short alkyl link, so the phenyl columns typically lack hydrophobic retention, and it exhibits low hydrolytic stability.

Figure 02: A Sample HPLC Pump

Phenyl columns are very successful in separating positional isomers, tocopherols, flavonoids, polynuclear aromatics, nitroaromatic compounds, active pharmaceutical ingredients, and other related compounds.

What is the Difference Between C18 and Phenyl Column?

HPLC instrument has a column that is useful in separating components in a mixture. There are different types of columns in HPLC instruments. C18 column and phenyl column are two such columns. The key difference between C18 and phenyl column is that the separation given by the C18 HPLC columns is lower compared to phenyl HPLC columns. Moreover, the resolution given by the phenyl column is higher compared to the C18 column. In addition, the stationary phase of the C18 column is a C18 compound such as octaldecylsilane, while the stationary phase of the phenyl column is made of short alkyl phenyl ligands that are covalently bound to the silica surface.

The below infographic presents the differences between C18 and phenyl column in tabular form for side by side comparison.

Summary – C18 vs Phenyl Column

The C18 column in HPLC is a column that uses a C18 substance as the stationary phase. Meanwhile, the phenyl column is a type of column that can be found in some HPLC instruments that have short alkyl phenyl ligands that are covalently bound to the silica surface. The key difference between C18 and phenyl columns is that the separation given by the C18 HPLC columns is lower than that of phenyl HPLC columns.

Reference:

1. “C18 Column / C18 HPLC Columns.” Labcompare.

Image Courtesy:

1. “202004 HPLC column” By DataBase Center for Life Science (DBCLS) – https://doi.org/10.7875/togopic.2020.144 (CC BY 4.0) via Commons Wikimedia
2. “HPLC pump” By Beige Alert – (CC BY 2.0) via Commons Wikimedia

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