How to Select the Right Guard Column

2024 Guide:

How To Select The Right Guard Column

An HPLC guard column is installed between the sample injector and analytical column to protect the analytical column from contaminants that might damage the stationary phase. Unfiltered particulates, precipitates, and high-retention compounds can be introduced from the sample which can ruin the retention of the stationary phase or block the analytical column.

A guard column helps prolong the serviceable life of an analytical column by trapping contaminants and preventing them from reaching the analytical column thereby preventing need for replacement and reducing costs.

Watch our video to discover how to choose the right guard column.

What is a guard column?

The guard column is a short column that is installed between the sample injector and the analytical column to protect the analytical column from contaminants that might adhere to or decompose the stationary phase, thereby adversely changing the retentive ability of the analytical column.

Contaminants include:

High-affinity compounds - compounds that adhere strongly to stationary phase which limit the analytical column's ability to retain target compounds. Examples include proteins and highly hydrophobic (non-polar) compounds in reverse phase chromatography.
Particulate matter - non-adherent materials but may deposit in the column due to size and block the column. Particulate matter includes precipitates that may form due to incompatibility with the eluent, buffer salts and particles from the pump and injector rotor seals (rubber) which gradually disintegrate as part of use. Particulates also increase the back pressure of the column.

Guard column types

There are many designs of guard columns available. It is necessary to be able to identify the particular type of guard column that is appropriate for the particular analysis requirements. In general, guard columns come in mainly two types:

In general, guard columns come in mainly two types:

Cartridge Guard Column

It is a cartridge which packing material is the same as the analytical column. The cartridge is put inside a special holder. This type is desirable for sample with high concentrations of interfering compounds and thus frequent replacement of the guard column is necessary.

Packed Guard Column

This is a short column that has been packed like analytical columns under high pressure. It is used in case of samples with high concentration of interfering compounds and it's not replaced very often.

There are many guard column products, each designed for a specific use. It is best to familiarize yourself with the manufacturer's description for each column line to see which one is suitable for your analytical requirements and is compatible with your analytical column.

GL Sciences offers several guard columns for protecting HPLC columns, designed for optimal operation in specific use:

Cartridge Guard Column E

Designed for general use. They are first choice cartridges when using standard size analytical columns. Recommended operating pressure is 20 MPa. The internal surface of the hardware is made of stainless steel.

Cartridge Guard Column Ei

The design is similar to E type, but the internal surface of the hardware is made of PEEK in order to avoid the adsorption of metal chelators.

UHPLC Guard Column

This type is for UHPLC and the maximum operating pressure is up to 80 MPa. The cartridge end to be connected to the column is fixed in order to avoid a dead volume.

GL Cart

Designed as low-cost columns to protect your expensive analytical column. The dimensions of GL Cart are 5 mm (length) × 4.6 mm (I.D.), compatible with I.D. 4.0 and 4.6 mm analytical columns.

Packed Guard Column, Packed Mini Guard Column

The packed and mini guard columns differ in their cartridge type. They are packed under high pressure and can sustain the analytical column’s performance.The packed guard column is 33 or 50 mm long and the mini guard column is 10 mm long.

SILFILTER STD C18

SIL FILTER STD C18 columns are a cartridge-replaceable guard column using monolithic silica gel. The porous silica gel is molded in one piece, eliminating the need for a column filter, unlike particle-packed columns. This feature eliminates clogging of the filter and allows visual confirmation of dirt accumulation in the cartridge guard column.

Preparative Guard Columns

Packed guard columns are for use in preparative HPLC columns. Guard columns are available for each packing material.

PREP Guard Cartridges

PREP Guard Cartridge Columns are cartridge-type preparative guard columns.

Guard column specifications

After choosing the right guard column type, select the specifications of the actual guard column to be used. The guard column needs to be compatible with the analytical column and thus will follow largely the close specifications.

Consult the following guide when selecting guard column specifications:

Packing material	Similar packing material as user column or a compatible material
Particle size	Same particle size as the user column. Larger particle size can also be used depending on the expected contaminants; larger particle sizes are still effective for particulate matter but not as much for highly retentive components.
Inner diameter (I.D.)	A guard column I.D. that is compatible with the user's column's I.D. as indicated by the manufacturer. This is usually the same diameter as the user's column's I.D.
Length	As short as possible to avoid dead volumes.
Column wetted material	For columns that do not allow for contact with any metals including the column, PEEK is usually used.

Flowchart for selecting GL Sciences guard columns

Column connectors

To connect a guard column to the analytical column, pre-column couplers are used. These joints are made of different materials. The pre-column coupler should be chosen according to the eluent (the same material as the guard and analytical columns) and the maximum operating pressure.

Pre-column Coupler W (PCTFE)

Pre-column Coupler SUS

Column Coupler for UHPLC

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