Abstract
The terahertz gap has a frequency ranges from ∼0.3 THz to ∼10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets.
Highlights
Terahertz measurements may well become the primaryFig. 1: electromagnetic spectrum of terahertz radiation (courtesy of SURA). method for the nondestructive determination of coating thickness, requiring little or no calibration for most coatings and substrates
The terahertz gap has a frequency ranges from ~0.3 THz to ~10 THz in the electromagnetic spectrum which is in between microwave and infrared
Terahertz radiation has been established for pharmaceutical applications when used as a spectroscopic technique in polymorph identification and quantification[10,11,12], phase transition monitoring[13,14] and hydrates recognition[15]
Summary
Fig. 1: electromagnetic spectrum of terahertz radiation (courtesy of SURA). method for the nondestructive determination of coating thickness, requiring little or no calibration for most coatings and substrates. Because it is non-destructive, tablet can be re-examined at later times to monitor stability or used for further functional studies with prior knowledge of the coating uniformity. The uniformity and consistency of the ibuprofen tablet coating is better conveyed by an image of the depth profile, analogous to the typical β-scan ultrasound format These images clearly show the difference in structure and thickness of the two coatings. The variations observed in the microscope image for the brand tablet, in particular the light central band within the darkest layer can be apparently seen This would be missed by a technique that made measurements at selected single point locations apparent in the microscope photograph. This results in an accurate depth profile for all geometries
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