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A large number of drugs are sensitive to light and therefore their formulated products may degrade during manufacturing, storage, and administration. This may result in potency loss, altered efficacy, and adverse biological effects. The use of the appropriate containers and packaging material can protect the products from the deleterious effects of light and UV radiation. The sensitivity of a drug to a particular spectral region of light may vary with its chemical structure, photoreactivity, and nature of the dosage form. The rate of a photochemical reaction may be influenced by the intensity/wavelengths of the radiation source and the transmission characteristics of the container, which is a critical issue for pharmaceutical and food industries and its related inspection and sorting activities. This makes the accurate measurements of spectral transmittance of great interest for many industries and vital activities in the medical, pharmaceutical and food sectors. This proposed new instrumentation scheme, including the associated corrections, can be applied for both the spectrally flat samples as well as the spectrally selective samples. Both sets of measurements, for both types of samples, presented in this work with the corresponding uncertainty level, which is spectrally and sample-dependent as shown. The used instrument, and related instrumentation scheme including the detailed equipment description are presented. To demonstrate the new concept, we measured the spectral transmittance of highly opaque samples, in the spectral range from 300 nm to 1000 nm, with and without optical attenuators to show the level of accuracy, repeatability and reproducibility. In this approach, to achieve better signal-to-noise when the sample transmittance approaches 10-6, additional attenuators can be used in the reference beam path. Measurements of some highly opaque samples has been shown, error sources have been investigated and corrected, with associated uncertainty been lowered. Uncertainty budget presented to show the uncertainty level of these measurements of extremely opaque samples. Level of uncertainty associated with the measurement of low transmittance level (< 0.01) at representative wavelength of “550” nm is evaluated to be “0.80%” (k=2).
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