Visualizing the Invisible

Latent Capsule Markings4(VSC images of the stained capsules under coaxial visible illumination (left) and under 400 – 680 nm excitation with 735 nm camera filter (right).)

Several broken gelatin capsules were found floating in a dark-colored beverage. Upon isolating these foreign objects from the liquid, it was observed that the capsule material had become darkly stained. A cursory visual examination showed no evidence of the capsule markings typically printed on pharmaceutical products. In an attempt to visualize any latent markings, the capsules were examined using a Visual Spectral Comparator (VSC). This instrument utilizes two sets of bandpass filters to transmit light of variable wavelengths to the sample, exciting and recording visible fluorescence. Using this technique, we were able to read the name of the manufacturer and the drug imprint code from the stained capsules.

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