5 Factors To Be Considered When Selecting Flash Column

HAWACH has summarized 5 important factors to be considered when you gonna choose the Flash column.

1. Packing material matrix
1.1 Silica gel matrix: high purity, low cost, high strength, easy chemical modification, but with limited pH range. Most silica-based packing materials are stable between pH 2-8, but the specially modified silica-bonded phase can be stabilized at pH 1.5-10.
1.2 Polymer matrix: wide application pH range, stable temperature (high temperature can reach above 80 degrees), low mechanical strength.

Chromatographic Silica Gel Flash Columns

2. Particle
2.1 Particle shape
Spherical particles provide lower column pressure, higher efficiency and stability, and longer column life when using a high-viscosity mobile phase; irregular particles have a larger specific surface area and a relatively low price.

2.2 Particle size
The smaller the particle size, the higher the column efficiency, and the higher the resolution, but at the same time, it will result in a higher column pressure drop. Choose 1.5-3μm packing to solve some complex samples. UPLC can use 1.5μm packing; another 10μm or larger packing can be used as a semi-preparative or preparative column.

3. Carbon content
The carbon content refers to the proportion of the bonded phase on the surface of silica gel, which is related to the specific surface area and bonding coverage. High carbon content improves column capacity, resolution, and analysis time, which is suitable for complex samples requiring high resolution; low carbon content’s analysis time is short, exhibits different selectivity, and is used for rapid analysis of simple samples and samples with high aqueous active phase conditions. Generally, the carbon content of C18 varies from 7-19%.

4. Pore size and specific surface area
Pore diameter and specific surface area are two concepts that complement each other. Small pore size and large surface area, and vice versa. Large specific surface area increases the reaction between the sample and the bonded phase, increases storage, sample loading, and resolution of complex components; the small specific surface area has fast equilibrium time, suitable for gradient analysis.

5. Pore volume and mechanical strength
Pore volume, also known as “pore volume” refers to the size of the void volume per particle. It can well reflect the mechanical strength of the packing. The packing with a large pore volume has a slightly weaker mechanical strength than packing with a smaller pore volume. Packings with a pore volume greater than 1.5 mL/g are used for size exclusion chromatography and low-pressure chromatography.