Since its discovery, stereochemistry remains important for development of pharmaceutical and biopharmaceutical substances. For the sake of drug safety and effectiveness, isomers need to be investigated closely. Therefore, the efficient separation both in analytical as well as in preparative scale of the isomeric forms is of high importance in the pharmaceutical sector. Chromatography is one of the key methods to obtain information regarding the different species.
Different methods are available for the separation of stereoisomers. Enantiomers are difficult to separate as they have exactly the same physical and chemical properties. They need special chiral phases. In comparison, many stereoisomers, including E/Z isomers can be separated using conventional phases such as C18 as these isomers differ in their physical or chemical characteristics.
One major pharmaceutical company developed a very easy, straight-forward approach to transfer their analytical methods to preparative scale. Their task was to collect, in a short time frame, information regarding cis-trans / EZ isomerism.
In this recent comparison study, the scalability of two methods from analytical to semi-prep scale using a pre-packed glass column was investigated. The API of interest, an E/Z isomer, turned out to be very challenging. A successful separation was obtained at a high pH 9.5 with high organic modifier content.
In principle, single-use/Flash cartridges could be an option, too. Due to lower pressure limits and limited chemical resistance this approach was not investigated further. Additionally, a large number of samples needed to be purified so the aim was to run the columns at the highest flow rates as possible. Due to the high pressure limit of the ECOPLUS glass column, higher flow rates could be applied and the throughput was increased.
Pre-packed glass columns are the perfect solution for the purification of an API isomer in a crude mixture:
