Manual for Normal Phase, Reversed-Phase Flash Column ( Part 1)

Flash column is packed with modified silica material. Introducing alkaline solvents (pH>7.0) or acidic solvents (pH<2.0) into the column will damage the flash column.

1. Introduction

Flash column is filled with silica gel which is a reversed-phase or polar gel-linked silica matrix material. Flash columns in the form of silica gel are used for normal phase (non-aqueous) conditions.
Reverse phase (C8, C18, ODS, RP-8, and RP-18) is usually used for reverse-phase conditions (phase).

sax chromatography flash column

Polar glue-linked types (APS, diol, CN, and NH2) can be used in normal phase and reverse phase conditions according to the application purpose. It is recommended not to use the same column under very different conditions. This is because the properties of the stationary phase will change under certain conditions, so under other conditions, column efficiency will be affected. It is also not recommended to use silica gel flash columns under reversed-phase conditions or reverse-phase flash columns under normal-phase conditions. This is because the process will have poor repeatability (comparison between each injection and between columns ).

2. Flash column aging

Before starting the analytical work, the column must be properly aged. An improperly conditioned column may cause problems, such as poor column efficiency or changes in separation conditions.

A. Aging under reversed conditions
To age, this type of column, first rinse with acetonitrile or methanol, and then equilibrate with your chosen eluent.

Before shipment, each flash column has been tested and aged. Therefore, it is not necessary to rinse with water during the first use).

If additives (such as buffers or ion-pair reagents) are used in the mobile phase, it is recommended to use a mobile phase with the correct ratio but without these additives for buffer washing. Buffer flushing should be performed at a low flow rate first, and then the normal flow rate will be used last.

B. Aging under normal phase conditions
Flash column efficiency may be severely affected by the bonding of water to the stationary phase. Drying (activation) or wetting (inactivation) of the column may be required. The solvent used may be water-saturated or anhydrous. Dry the column can use anhydrous methylene chloride.

C. Special instructions for polar bonding columns
Since these columns can be used in reversed-phase or normal phase conditions, before aging, you must first check whether the eluent or eluent you want to use is miscible with the solvent packaged in the flash column. If these solvents are not miscible, you must first use a suitable buffer solvent to rinse.

3. Eluent

Pay attention to section 1 and section 2. Be sure not to use buffers with a pH lower than 2 or higher than 7, because they will change the nature of the stationary phase. It is best to use polar bonding columns between 3 and 5. Before use, the eluent should be degassed and filtered with a 0.5-micron filter membrane to avoid detection and pumping problems.

Be sure to check for microbial growth in the aqueous solution before you start using the system, otherwise, your column will become clogged and the column pressure will rise to unacceptable levels.

4. Flow and pressure

Note: Maximum pressure: stainless steel column: 4500psi; glass column: 3000psi
To increase or decrease the flow rate, small interval changes are required to prevent disturbance of the packed bed.

If you want to replace the column, reduce the flow rate to 0 and wait for the eluent to completely flow out of the column (2 minutes).
Removing the column without waiting for a decrease in pressure will damage the column.
The high column pressure is generally the result of incorrect use of the column.

The use of guard columns (see section 6) will prevent contaminants from depositing on the analytical column.

5. Sample preparation

The key to maintaining the longevity of the column is proper sample handling before injection. You must prevent the pumping of compounds that are highly hydrophobic/polar from the mobile phase into the column, whether from the mobile phase or the sample. In particular, it is forbidden to introduce particulate impurities. These will eventually increase the operating pressure and are very difficult or impossible to remove.