Chromatography Forum

dear all,
chiral seperation seems to be new for me. i would like to know the mechanism of seperation and column chemistry of it. how does the dextro and laevo get seperated even though they have same chemical structure and molecular weight?

with regard
pliva

The short answer is "secondary interactions". Most of the retention is driven by the same forces that apply in other types of chromatography (e.g., hydrophobicity for RP or polar interactions for NP) but with a chiral stationary phase, one of the analyte enantiomers will "fit" a little bit better/worse than the other.

Usually HPLC has to do with stechyometry than molecular weight and chemical structure (molecules are just molecules and they do not carry any chemistry degree!).

That means that interaction inside a column has more to do with the actual structure, their shape, their electron clouds... in a chiral column, ligands are developed to interact with some parts of the structure, as Tom explained - they just fit better or worse!

Since enantiomers maybe defined as reflected images of each other, it is easy to close your eyes and imagine that they will in fact interact differently with some molecules at chromatographic bed.

The difference in interaction of two enantiomers toward another chiral entity has been called diasteriomeric interaction. This is what gives rise to diasteriomers as well.

The short answer is "secondary interactions". but with a chiral stationary phase, one of the analyte enantiomers will "fit" a little bit betterthen the other . I give you one example lets consider your two hand both are enantiomers so if you shake right hand with other person right hand you can hold it hand better and longer as compare left hand with right hand that same case in separation of chiral compound. the one enantiomer in can make better interaction with stationery phase then the other
thanks
z