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Column length and efficiency If the column length is reduced, the number of theoretical plates in the column will be correspondingly reduced and therefore the resolution of the HPLC system.

Symptoms of deterioration are poor peak shape, split peaks, shoulders, loss of resolution, decreased retention times, and high back pressure. These symptoms indicate contaminants have accumulated on the frit or column inlet, or there are voids, channels, or a depression in the packing bed.

Guard columns are used to protect the analytical column and extend its lifetime. Retention gaps also act as guard columns, but their primary goal is to improve peak shape by focusing the sample components whenever introducing a large liquid sample onto the column.

HPLC guard columns and guard cartridges protect analytical, semi-prep and preparative HPLC columns. They help by removing particulate contaminants and highly absorptive compounds from samples, prolonging column life. Ideally, guard columns should contain the same stationary phase as the analytical column.

How can I prolong column lifetime? Sample preparation. Prefiltering samples prior to injection onto the column can help to limit the addition of particulates to the system.Mobile phase. The mobile phase is another factor that influences column lifetime.In-line filters and guard columns.Maintenance.

If the column was properly flushed after use and stored in 100% organic solvent such as acetonitrile, the column will survive for many years.

General advice: Replace the guard column when the nature of the sample is changing, when backpressure is increased about 10-15%, or by schedule/time basis (for example, every 200 to 500 injections ? depending on the injection volume and sample purity).