Once you know which guard column system you need, the next step is choosing an LC guard cartridge with the packing and dimensions that best match your analytical column. In order to obtain maximum protection without compromising selectivity or efficiency, you should select an LC guard cartridge that contains the same packing material—both stationary phase and silica—as your analytical column. For example, the best LC guard column to use with a Raptor Biphenyl 2.7 µm analytical column is a Raptor Biphenyl 2.7 µm guard cartridge.
In addition to choosing a guard cartridge packing that matches your analytical column, you need to select an LC guard cartridge with the correct inner diameter (ID). A good general rule is that the LC guard column cartridge ID should be the same as, or one size smaller than, the ID of the analytical column. So, a 4.0 mm ID guard cartridge should be used with a 4.6 or 4.0 mm ID analytical column, while a 2.1 mm ID guard cartridge is recommended for 3.2, 3.0, and 2.1 mm ID analytical columns.
See our LC guard column selection guide for details on which guards are compatible with which specific analytical columns.
