Terahertz hyper-spectral imaging of lab-prepared versus commercial paracetamol tablets and potential applications

Terahertz spectroscopy and imaging have proved to be a versatile tool for the studying of drugs and pharmaceutical analysis. Particularly, this method has been employed to map the coating layer of pharmaceutical tablets, to identify the polymorphism of active pharmaceutical ingredients (APIs), etc. In this paper, Terahertz (THz) hyper-spectral imaging using time-domain spectroscopy technique has been applied to image a commercial packaging of paracetamol tablets, showing the ability to penetrate through both cardboard of the box and plastic cover of the blister pack. The advantage of THz time-domain spectroscopy (THz-TDS) is that not only the dimensional imaging was captured but also the spectral information was registered. A comparison between THz spectrum of commercial and lab-prepared paracetamol tablets shows the presence of a certain amount of α-D-lactose monohydrate at the absorption peak of 0.53 THz. Any API or excipients can be detected if their fingerprints fall in the measureable range of the system. This work opens up a possibility of using THz-TDS to non-destructively control the quality of pharmaceutical products while they are still in their packaging. This potential capacity is important as for the identification of the APIs as well as changing of unwanted physical (and hence biological) properties during the shelf-life of the product.