The Reason for Increase of Column Pressure During Use

irregular c18 flash column chromatography

Flash column pressure has something to do with the form of silica gel, the mesh number, the synthesis condition of filler, the condition of column packing, the mobile phase, and the temperature when analyzing.

For different manufacturers’ new flash columns (such as Spherical Diol Flash Column and Spherical Phenyl Flash Column) their column pressures may be differed by 4 to 5 Mpa under the same condition of mobile phase and temperature. Especially for the low-end and high-end products, the difference is more obvious.

Form of silica gel: The form of silica gel used in the flash column, such as irregular or spherical particles, can influence the pressure. Irregular particles may have more significant void spaces between particles, leading to higher pressure compared to spherical particles.

Mesh number: The mesh number refers to the size of the silica gel particles in the flash column. Smaller mesh numbers indicate larger particle sizes. Columns with larger particle sizes generally have lower pressure compared to those with smaller particle sizes.

Synthesis condition of filler: The synthesis condition of the filler material, such as the surface area, pore size distribution, and packing density, can affect the pressure during flash chromatography. These characteristics influence the flow dynamics and the resistance to solvent flow, thereby impacting the pressure profile.

Column packing: The quality of column packing, including the packing density and uniformity, can impact the pressure. Well-packed columns with a consistent bed density generally exhibit lower pressure compared to poorly packed columns with uneven packing or voids.

Mobile phase: The composition and viscosity of the mobile phase used in flash chromatography can affect the pressure. Solvents with higher viscosities or mixtures with higher proportions of viscous solvents can lead to increased pressure.

Temperature: The temperature at which the flash chromatography is performed can influence the pressure. Changes in temperature can affect the viscosity of the mobile phase and the analyte’s solubility, thereby impacting the pressure profile.

Particle Accumulation: Over time, particulate matter from the sample or contaminants can accumulate on the stationary phase of the column. This buildup can lead to increased resistance to the flow of the mobile phase, resulting in higher column pressure.

Column Overloading: Exceeding the recommended sample load capacity of the column can lead to poor separation and increased pressure. Overloading may cause increased backpressure and decreased column efficiency.

Particle Size and Pore Size Mismatch: Using a mobile phase with a different composition or properties than the phase for which the column is designed can cause particle size and pore size mismatch. This can result in poor flow and increased pressure.

Mobile Phase Issues: Changes in mobile phase composition, such as an increase in viscosity or the presence of air bubbles, can contribute to elevated column pressure. Ensure that the mobile phase is properly prepared and degassed.

Blocked Fittings or Tubing: Blockages or restrictions in the flow path, including fittings, tubing, or the injector, can lead to increased backpressure. Check for any obstructions and clean or replace components as needed.

Column Degradation: Over time, columns can degrade due to chemical interactions or wear and tear. This can result in a loss of efficiency and an increase in pressure. Regular column maintenance and replacement are essential to prevent degradation issues.

Temperature Fluctuations: Changes in temperature can affect the viscosity of the mobile phase and the efficiency of the separation. Sudden temperature changes or improper temperature control may lead to increased pressure.

Air Bubbles in the System: The presence of air bubbles in the mobile phase or the sample can disrupt the flow and cause pressure spikes. Proper degassing of the mobile phase and careful sample handling can help prevent this issue.Improper Flow Rate: Running the chromatography system at a flow rate higher than recommended for the column can lead to increased pressure. Ensure that the flow rate is within the specified range for the column.

Instrument Issues: Malfunctions or issues with the HPLC instrument, such as problems with the pump, injector, or detector, can contribute to increased pressure. Regular instrument maintenance and troubleshooting are essential.

It is important to consider these factors and optimize the flash column and experimental conditions to achieve efficient separation with minimal pressure buildup. Adjusting the column packing, selecting an appropriate mesh number, optimizing the mobile phase composition, and controlling the temperature can help manage the column pressure during flash chromatography.

The above-mentioned is decided by the silica gel and production condition of the manufacturers, and the existence of difference is very normal. At the same time, column pressure also has something to do with column efficiency. In general, the flash column with high column efficiency has relatively high column pressure, while the flash column with high column pressure does not always have high column efficiency.

Normally, there are two types of pressure increase during the use of a flash column. One is that the column pressure increases slowly as the time of use extends, and this is normal. The other is that the column pressure suddenly increases a lot during use. This phenomenon is always caused by the improper operation of laboratory workers. They mainly do not filter the samples before using the flash column.