Leakage Removal in Operation
Mobile phase leakage sometimes occurs during filtration, the possible reason is that the filter membrane is misplaced (a little biased) or the joint is a little misplaced, resulting in the flow phase leaking out of the gap. Therefore, during operation, a small amount of mobile phase should be poured into the bottle to observe whether the liquid is leaking and start filtering, if there is no leakage, the mobile phase should be added to the container gradually. Another matter needing attention is that the column should be flushed with pure water mobile phase as far as possible after operation, or the strong polarity of water will damage the column and lead to a decrease in column efficiency and accuracy.
Improper Combination Removal in Application
Read the instructions attached to the chromatographic column carefully before use, and pay attention to the scope of the application, such as pH range, mobile phase type, etc. In the process of operation, it is better to use the required mobile phrase, protective column. When the flash column is not in use, rinse with formaldehyde, remove and close two stages of preservation, do not rinse the column under high pressure, and do not use silicon bonds.
Flash column chromatography has been used widely in organic chemistry since it was first published. However, the guidelines of flash column chromatography are not translated or spread correctly. There are still several common problems when experimenters do experiments with flash column chromatography.
First, the increasing sampling size will lead to the reduction of the resolution. Compared with HPLC, the resolution of flash column chromatography is medium level. And thus the increase in the sampling number will only aggravate the situation, the reduction of the resolution.
Second, the optimum velocity depends on the length and width of the flash column and the properties of the gel. The longer and narrower columns will provide more theoretical plates to affect the flow rate.
Finally, the resolution is affected by the stationary phase. If the stationary phase or the gel arranged on the column is more homogeneous and has a smaller particle size, it provides better resolution. The smaller the particle size is, the larger the surface area is and the higher the resolution is.
Insufficient Eluent Volume: Using too little eluent volume or eluting too slowly can result in incomplete recovery of compounds.
Inadequate Mixing of Solvent: If the solvent system is not mixed properly, it can lead to uneven elution.
Inconsistent Column Performance:
Inadequate Equilibration: Failing to properly equilibrate the column before sample loading can result in inconsistent results.
Column Degradation: Overuse or improper storage of the column can lead to decreased performance.
Solvent mismatch occurs when the solvents used in the mobile phase are not compatible with the stationary phase or with each other. This can lead to poor separation and compromised purification results. Choose Compatible Solvents: Select solvents that are compatible with both the stationary phase material and the compounds you are trying to separate. Consider the polarity and compatibility of the solvents.
Inconsistent Flow Rate:
Inconsistent flow rates can lead to irregularities in the chromatogram, affecting the separation.
Check for Clogs: Inspect the system for any clogs or obstructions, including frits or tubing, and clear them if necessary.
Verify Pump Settings: Ensure that the pump settings are correct and that the flow rate is stable. Adjust as needed.
Monitor Pressure: Monitor the pressure in the system to ensure it remains within the recommended range for the column.
Inadequate Column Packing:
Inadequate column packing can lead to uneven flow and poor separation.
Repack the Column: If you suspect inadequate packing, consider repacking the column. Follow proper packing procedures to ensure uniform packing density.
Check for Air Pockets: Ensure there are no air pockets or voids in the packed column. Use proper techniques to eliminate any trapped air.
It’s important to address these issues systematically and in the order presented. Start by confirming the compatibility of solvents, then check for and resolve any flow rate inconsistencies. If issues persist, consider examining the column packing and repack if necessary. Regular maintenance and careful attention to these factors can greatly improve the efficiency and effectiveness of flash column chromatography.