​Flash chromatography is performed according to the method described by William Still¹. While still in use to a degree, the role of open glass chromatography columns has been diminished as the features and benefits of automated flash chromatography instruments expand. Comparatively, open glass chromatography columns are more cumbersome to use, yield less accurate results that are difficult to reproduce, and have additional safety concerns.

​What are glass chromatograp​​hy columns?

Glass chromatography columns are hand-packed columns can be packed dry or by using a wet-slurry of silica or other adsorbent. The chemist will normally pack the column with air-pressure or by pulling vacuum on the outlet of the column causing the silica bed to pack and compress. Once the column is packed, the user then will carefully load their sample to avoid disturbing the silica bed. After the sample is loaded the chemist will run the column using their solvent mixture gradient. Only isocratic or step gradients are possible with open columns. The column requires more time to run and needs continual monitoring and management of solvent and fractions. A large number of TLC plates are required to identify the fractions of interest due to the lack of any detector. ​​

​Advantages of automated flash colu​mns

Open columns are made of fragile glass that, when broken, requires cleanup of sharp shards and loose silica. The glass columns need to be packed and unpacked at the end of the experiment, exposing students to silica dust, solvents, and any retained compounds on the column. Glass columns need to be inspected carefully for any defects in the glass to avoid any safety concerns from using glass under pressure.

Automated flash columns such as Teledyne LABS’ RediSep columns​ are self-contained, so there is no exposure to silica gel or any products or solvents left on the column after the experiment is finished. The columns are optimally packed, giving improved resolution and reducing the possibility of co-eluting peaks. Although the columns are packaged in plastic, there is reduced solid waste because the detector shows which fractions should be combined, rather than using thin layer chromatography (TLC) plates to see when compounds elute.

Automated systems allow experimentation with gradients and show the relationship between gradient steepness and resolution between peaks better than open columns. As there is no need to pack or clean columns, and the purifications are faster, more samples can be run in a given time, offsetting the parallel runs that can be done with open columns.

Time in the lab can be optimized and errors decreased by removing the constant supervision and labor required by a manual procedure. An automated purification can take as little as 14 minutes total, when subtracting the column run time from the total time taken. This is a clear testament to the efficiency of an automated purification.

It is much easier to learn and perfect the methodology of product purification using the automated system as compared to a manual one. This is because the manual glass chromatography column purification method is more complex and requires much more practice to become familiar with than an automated purification.

An automated system such as the Teledyne ISCO CombiFlash NextGen 300+ is initially a more expensive investment than manual column glassware materials. However, the majority of synthesized products for public use are purified by automated means; therefore it should be essential to allow undergraduate chemistry students to have the experience of purifying products using automated instrumentation.

Although an initial investment in an automated instrumentation is required, it is more economical to run automated purifications and additionally can allow students to be better prepared for their careers as chemists.

Reference​​

¹ “Rapid Chromatographic Techniques for Preparative Separation with Moderate Resolution." Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43 (14), 2923-5​

​F​​requently Asked Questions

What are the 4 types of column chromatogr​​​aphy?

Adsorption column chromatography, partition column chromatography, gel column chromatography and ion-exchange column chromatography.

What glassware is used in column chromato​​​graphy?

Borosilicate glass is commonly used for chromatography columns.