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This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).
Raman spectra of theophylline anhydrate samples conditioned at 19%, 38%, 63%, and 82% RH, and at 300 mbar for nine days. The Raman spectra show the same spectra as the anhydrate reference. The sample conditioned at 99% RH shows the specific theophylline monohydrate peak at 1171 cm-1.