Overnight or short-term storage:  If the same method will be used again the next day, and the mobile phase has low buffer/salt content, the column may be left on the system under suitable low-flow conditions. In this case, full re-conditioning of the column may not be necessary before the next sequence, provided the same mobile phase and method conditions are used. However, if the mobile phase contains appreciable buffer or salt, prolonged static storage in the mobile phase should generally be avoided because of the risk of salt precipitation and microbial growth.

Mid-term storage: After completing analysis, if the column is not being used for an extended period, it is typically recommended to wash the column by passing through about 10 column volume of the mobile phase containing 10% methanol in water. This will help to flush the salts out from the column and also prevent the possible precipitation of the buffer. After the salts and buffer have been removed, flush the column with 100% methanol which is an excellent solvent to remove the fed state biorelevant components for approximately 15 column volumes. Afterwards, the column can be detached and sealed with end plugs, or it can remain attached to the instrument.

Long-term storage: After thorough cleaning, the column should be stored in a solvent recommended by the column manufacturer. For columns used with fed-state biorelevant media, methanol-rich or isopropanol-rich storage solvents are often preferred because they help reduce the risk of column drying and microbial growth. Suitable storage solvents may include methanol: water (80:20, v/v) or isopropanol: water (80:20, v/v), depending on the column chemistry and manufacturer’s instructions.