Analysis of pharmaceutical tablets and drugs by Raman spectroscopy

Raman confocal microscopy is widely used in pharmaceutics. Such technique allows identify chemical compounds and molecular conformers in various drugs. Measuring the distribution of the ingredients in the tablet is important for monitoring the manufacturing process and impurity testing.

In this application note Confotec® MR520 instrument is used for study of the pharmaceutical tablet containing two active components – Aspirin and Paracetamol, to demonstrate capabilities of Raman technique. These active ingredients should be combined uniformly to produce a quality tablet. Homogeneous distribution of components will improve compression characteristics of tablets, their hardness and lifetime.

The tablet exhibits two characteristic types of Raman spectra (Fig.1). Spectra in Fig.1 correspond to two main components of tablet: Aspirin and Paracetamol. Raman spectrum of Paracetamol consists characteristic bands at 1650 cm^-1 (C=O) and 1612 cm^-1 (N-H). Raman spectrum of aspirin has the characteristic bands at 1606 (C-C) and 1622 cm^-1 (C-O stretching vibrations of the carboxyl group).

Characteristic Raman spectra of Aspirin and Paracetamol used to map distribution of chemical compounds in the tablet are displayed in Fig.2, where green color corresponds to Aspirin and red color corresponds to Paracetamol.

It is possible to see homogeneous distribution of active components within the investigated tablet (see Fig.2).

Raman confocal microscopy is a powerful tool for pharmaceutical applications. Distribution of Aspirin and Paracetamol components within the tablet has been studied with the high spatial resolution.

Publication date: 22 November 2013

Fig.1. Raman spectra of Aspirin (green) and Paracetamol (red).

Fig.2. Distribution of chemical compounds in the tablet. Green color corresponds to Aspirin. Red color – to Paracetamol.