Brief Description Of Flash Column Chromatography
Flash column chromatography, also known as a flash column, is a fast separation method, but it does not sacrifice resolution as others have said.
In the general column chromatography process, it is usually accompanied by lateral diffusion, which will greatly reduce the resolution, so when walking the column, you should try to shorten the column chromatography time, especially to avoid the column overnight. The purpose of the flash column, that is, without sacrificing exchange efficiency (adsorption and desorption), use the fastest possible flow rate to reduce this lateral diffusion.
Flash column is not blindly pressurized to achieve the fastest flow rate; the flow rate has certain requirements. Regardless of the thickness of the column, the flow rate is generally adjusted to the rate of eluent reduction in the column is 2cm/min. This is an experience speed, adjustments to it should consider the balance of exchange efficiency and lateral diffusion.
Similarly, VLC (Vacuum Column Chromatography) is also a very good column chromatography technique. It uses TLC’s “multiple unfolding” techniques so that the two samples to be separated immediately overlap (on TLC). Get better separation. Unfortunately, such good technology, some people think that it is used for rough separation.
For synthetic and medicinal chemistry, it is often necessary to screen a large number of potential compounds in the early stage. Once the relevant active compounds are found, the compounds need to be mass-produced. At this time, the previous milligram-level synthetic preparation methods need to be modified and upgraded to develop a new set of synthetic purification preparation process to meet the clinical testing and application of a large number of later compounds. In this process, the process development of compound purification is a very important link; on the other hand, in the field of natural products, when high value-added monomers are found, how to obtain the target monomers in large quantities through purification means has been These are the core problems that need to be solved.
The process development mentioned above for purification and preparation, whether in the field of medicinal chemistry of natural products, is a problem that requires scientists to spend a lot of manpower and material resources to explore and solve. Generally, improvements are made in two aspects: 1. Change the synthetic route and try to use the recrystallization method to reduce the cost; 2. Use column chromatography above 100 grams to prepare purification technology.
In addition to the transformation of the synthetic route of the process, efficient column chromatography amplification technology is also a very critical step. In terms of the linear gradient method used, more solvent is consumed in practical applications. Therefore, the optimization of the method is urgently needed and very necessary. The success of the project is often closely related to this. Through the optimization of the method, we can isolate the most samples with the least time and solvent consumption.
Isocratic or step gradient methods are used for optimization. On the other hand, a column with higher column efficiency can help increase the sample load and speed up the separation.
Contains 5 simple steps:
TLC spot plate to test various mobile phase combinations; use a column with higher column efficiency; create a linear gradient method based on the TLC spot plate information; based on the results of the previous gradient method, use the gradient method to optimize; gradually increase the loading volume, to find the best sample loading range, while ensuring that the linear velocity of the method does not change.
This method can greatly reduce the time and solvent consumption, thereby reducing the cost of the final product. The use of the step gradient method greatly increases the efficiency of scale-up production, while reducing the consumption of solvent and time costs. On the other hand, for reversed-phase preparation, the optimization of the five-step method is also applicable.