Determination of enantiomeric compositions of pharmaceutical products by near-infrared spectrometry.

A new method for the determination of enantiomeric compositions of a variety of drugs including propranolol, atenolol, and ibuprofen has been developed. The method is based on the use of the near-infrared technique to measure diastereomeric interactions between an added carbohydrate compound and both enantiomeric forms of a drug followed by evaluation of the data by partial least square analysis. The fact that the method works well with all three macrocyclic carbohydrates with different cavity sizes (i.e., alpha-, beta-, and gamma-cyclodextrin) and with sucrose, which is a linear carbohydrate, clearly demonstrates that it is not necessary to have inclusion complex formation to produce effective diastereomeric interactions. Rather a simple adsorption of the drug onto a carbohydrate is sufficient. Since inclusion complex formation is not a requisite, this method is not limited to the three drugs evaluated in this study but is rather universal as it can, in principle, be used for the sensitive and accurate determination of enantiomeric compositions of many different types of drugs with only about 1.5mg/mL concentration and enantiomeric excess as low as 0.80%, in water or in a mixture of water with organic solvent. Furthermore, it does not rely on the use of rather expensive carbohydrates such as cyclodextrins but is equally as effective even with a simple and inexpensive carbohydrate such as sucrose.