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DR-CD accessory for the determination of enantiomeric ratio – MOS-500 – Spectroscopy – Application Note 23

Latest updated: May 6, 2020


This application note describes the use of the cryo accessory combined to an external cryostat which extends the temperature range of the SFM to -90°C allowing for these lower temperature regime reactions to be observed. The reaction between 2,4 dinitrophenyl acetate (DNPA) and sodium methoxide in organic solvents is used to illustrate the use of this accessory in a SFM equipped with the appropriate o-rings.



The preparation of pure enantiomers for the pharmaceutical industry is part of mandatory safety requirements. Circular Dichroism is one technique to determine enantiomeric purity and it can be applied directly on solid samples. Circular Dichroism measurements on solid samples have been done for years on pellets when sample proved to be insoluble or was showing structural change when changing media. The preparation of pellets is not straightforward and is also time-consuming. To use an integration sphere for measuring Diffuse Reflectance (DR-CD) is an alternative to pellets that can be implemented in a few minutes on MOS-500. This application note illustrates the use of DR-CD accessory to determine the enantiomeric purity of some alanine preparation (powder mixture of L and D forms).


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