Catalog Number - 40018-25P

The 40018‑25P Cogent Bidentate C18™ HPLC Column is a long‑format analytical column designed for separations that demand maximum resolving power and extended retention. Built on Cogent TYPE‑C™ silica hydride technology, this column delivers unique selectivity, fast equilibration, and exceptional chemical robustness, even under aggressive method conditions.

The stationary phase features an aliphatic C18 chain bonded via two direct silicon–carbon bonds (bidentate attachment) to a silica hydride surface. This non‑traditional reversed‑phase chemistry creates a surface that is highly hydrophobic yet versatile, enabling retention of analytes that often show weak or inconsistent retention on conventional silica‑based C18 columns.

Unlike standard C18 phases, the Bidentate C18™ can operate with 100 % aqueous mobile phases without phase collapse and tolerates very low pH conditions (below pH 2) with no damage. These attributes allow method development across a wider operating window than traditional reversed‑phase materials.

The 250 mm column length provides the highest plate count in the Bidentate C18™ analytical lineup, making this column the preferred choice when additional separation between closely related compounds or longer retention times are required.

Why Choose the 250 mm Bidentate C18™ Format

This column size is commonly selected when:

• Closely related or isomeric compounds require maximum resolution

• Shorter columns (50–150 mm) do not provide adequate separation

• Extended retention improves method selectivity or robustness

• Gradient or isocratic methods benefit from increased plate capacity

When combined with TYPE‑C™ silica hydride chemistry, the longer length maintains stable retention and long column life despite higher interaction time.

Key Features

Cogent TYPE‑C™ Silica Hydride Technology

• Reduced silanol activity and secondary interactions

• Faster equilibration than conventional C18 columns

• Extremely robust column lifetime

Bidentate C18™ Bonding

• Two‑point attachment via direct Si–C bonds

• Unique selectivity not achievable with standard C18 phases

• Retains strongly hydrophobic and select hydrophilic analytes

Maximum‑Resolution Analytical Geometry

• 4.6 mm ID × 250 mm length

• Highest plate count and separation power in the family

• Ideal for complex and closely eluting analyte mixtures

Exceptional Method Flexibility

• Compatible with 100 % aqueous mobile phases

• Stable at very low pH (below 2)

• Suitable for aggressive or unconventional reversed‑phase methods

Typical Applications

• High‑resolution analytical HPLC

• Closely related compounds and isomers

• Methods requiring extended retention

• Low‑pH reversed‑phase separations

• Aqueous‑dominant mobile‑phase methods

• Method development and confirmation analyses