Raman spectroscopy shows mettle as fake drug detector

A systematic study of Raman spectroscopy as a tool to distinguish between counterfeit and genuine pharmaceuticals has shown it can detect even tiny discrepancies in ingredients.

The scientists behind the study - from Aalen University in Germany - used Raman and a technique known as principle component analysis (PCA) to analyse a large set of model tablets which varied with regard to active and inactive ingredients as well as their physical properties.

They also showed that it was possible to use the technique to detect early small chemical changes caused by inappropriate storage conditions for a commercial soluble aspirin product, suggesting it also has a role to play in monitoring substandard medicines.

"The discrimination between samples with different coatings, a varying amount of active pharmaceutical ingredients and a diversity of excipients were possible," report the researchers, who have published their findings in the Journal of Pharmaceutical and Biomedical Analysis (112 (2015) 70–78).

Raman is particularly suited to this endeavour as it is easy to carry out with minimal sample preparation, is non-destructive and can provide measurements through packaging and tablet coatings.

A series of model tablets containing two active pharmaceutical ingredients (quinine sulfate dihydrate and caffeine), eight excipients, an organic dye and two coating materials, were produced to put the analytical approach through its paces.

Raman and PCA was able to distinguish between tablets with varying APIs, excipients and coatings, although the researchers determined that it was unable to detect changes in other production variables - such as press power, mixing quality and granulation.

Raman and PCA analysis is a "fast and powerful tool for the characterisation of samples which are suspected to be counterfeits," write the authors.