Guard Columns: Why use them

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	HPLC Product Index
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Keeping your HPLC Columns
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Why Use a Guard Column?

Why Use a Cogent i-Column™?

Integral Guard Kit Shown

Particulate Contamination

Particles collect in an HPLC column’s inlet frit or in the first millimeter of the packed bed. These valuable columns are usually discarded to avoid degradation of analysis such as peak tailing and split peaks. Instrument downtime can occur which can be very costly to your lab.

Chemical Contamination

Another source of problems are compounds that irreversibly bond to the stationary phase and are often injected into analytical columns. These compounds cause permanent damage to columns that are not protected by a guard column. Shifting of retention time and loss of resolution often results.

A Particulate and Chemical Filter

Particulate contaminants will be filtered by the guard column's frit before they collect on the analytical column. All dissolved and non-dissolved contaminants will be retained by the guard column's stationary phase before they destroy the analytical column.

Mobile Phase Destruction of Columns

Most chromatographers use mobile phases and additives that will destroy silica particles in an HPLC column even if it is end capped and well shielded. Certain solvents are more destructive than others. The use of common buffers, water and even methanol are among those solvents that will shorten the life of your columns.

A guard column provides saturation of your mobile phase with silica by “bleeding” silica into the mobile phase instead of from the analytical column. This can be achieved without the loss of resolution or performance by using a Cogent™ Guard Column. When the guard column is destroyed, replace it with another cartridge in minutes.

According to most experts, a guard column can increase the usable life of your columns by a factor of four. You will save money and valuable time.

Helpful Hints

All mobile phases, samples and additives should be filtered through a .45µm syringe filter.
It is recommended that guard columns are packed with the same stationary phase as the analytical column to be protected. (Eliminate the possibility of any loss of performance or selectivity.)
Pump seals and rotor seals should be replaced on a routine basis.

Relative Solubility of Silica

Methanol: Low
Water: High
Buffers: Very High

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