High performance liquid chromatography HPLC , enantiomeric purity

Because of the instability of cyanohydrins, the characterization of cyanohydrins mostly should be hydroxyl protected. In 2001, Gerrits et al. [26] investigated the influence of solvent composition on the stability of unprotected cyanohydrins and then described a method to analyze unprotected cyanohydrins (with regard to enantiomeric purity and conversion) via chiral high-performance liquid chromatography (HPLC). Hernandez et al. [27] and the groups... 

The enantiomeric purity of the sulfamidates 55a and 55b was established using Whelk 0-2 chiral high-performance liquid chromatography (HPLC) <2005TA1583>, and in each case chiral HPLC confirmed an enantiomeric excess of at least 97%. These two sulfamidate oils proved to be very stable when stored for up to a year at — 20 °C. 

Apart from being able to distinguish between diastereomers the analytes must also be separated from all other potentially chiral interferences that either are endogenous to the mixture or are likely to be produced in the derivatization reaction. Accordingly interest has been directed towards the separation of drug enantiomers by high performance liquid chromatography (HPLC). The technique can provide a quick, reliable and sensitive method for chiral resolution and for the determination of the enantiomeric purity. 

High-performance liquid chromatography (HPLC) techniques have been used lately for enantiomeric separations of benzazocine having a chiral biaryl axis <1998TA3497> and in analytical methods for purity determination <1996JME669, 1997JME1578, 2000JME2362>. 

The Cahn-Mangold-Prelog (R,S) system was used here to describe the chirality of molecules, and the enantiomeric excess (e.e.) to quantify the enantiomeric purity. The e.e. values, which are usually obtained from direct concentration determinations by high-performance liquid chromatography (HPLC) or gas chromatography (GC), have replaced the operational term optical purity in the last decades due to a high sensitivity of optical rotations to experimental conditions [17]. However, e.e. values that were calculated in several cases from the optical rotation and the dl system of a-amino acids based on the optical rotation were also adopted from the literature. On the other hand, neither the directions in which enantiomers rotated plane-polarized light (+ or —) nor specific rotations a were stated here. 

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