Abstract
Optical coherence tomography (OCT) has recently been demonstrated as a powerful tool to image through pharmaceutical film coatings. Majority of the existing systems can, however, resolve film coatings for thickness greater than 10 µm. Here we report on an ultra-high-resolution (UHR) OCT system, with 1 µm axial and 1.6 µm lateral resolutions, which can resolve thin coatings at approximately 4 µm. We further demonstrate a novel application of the system for differentiating generic and branded suppliers of paracetamol tablets.
Highlights
IntroductionTo assess the coating quality (thickness uniformity, roughness, defects), various analytical techniques have been proposed
Pharmaceutical film coatings are polymeric films formed from an aqueous latex dispersion, that are applied for various purposes such as protecting the active pharmaceutical ingredients (APIs) from light and moisture, improving the visual appearance, taste masking, and in some cases, brand differentiation.More advanced coatings serve a functional purpose such as controlling the release rate of the APIs [1].To assess the coating quality, various analytical techniques have been proposed
It should be noted that even though cross-sectional images (B-scans) at the center of the tablets are shown, the system can, in principle, achieve an illumination area of approximately 1-mm diameter. a 3D datacube consisting of 8 raw B-scan data were acquired for each measured tablet
Summary
To assess the coating quality (thickness uniformity, roughness, defects), various analytical techniques have been proposed Examples of these techniques include vibrational spectroscopic methods like near-infrared (NIR) [2] and Raman spectroscopy [3] as well as imaging methods such as nuclear magnetic resonance imaging (NMR) [4], X-ray micro-tomography (XμCT) [5], terahertz pulsed imaging (TPI) [6] and optical coherence tomography (OCT) [7]. Amongst all these methods, TPI and OCT are attractive because coating thickness can be measured directly where the only unknown is coating refractive index (RI), as opposed to spectroscopic methods that require calibration against a priori developed chemometric models. The achievable resolutions of TPI are 150–250 μm in the lateral direction and
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