Application of FTIR spectroscopic imaging to study the effects of modifying the pH microenvironment on the dissolution of ibuprofen from HPMC matrices

Abstract This work presents the novel application of attenuated total reflection–Fourier transform infrared spectroscopic (ATR–FTIR) imaging to study the dissolution of ibuprofen form tablets in which the internal pH of the matrix has been modified by addition of acidic and basic powders to the formulations. Acidic additives to the matrix retarded the dissolution of crystalline ibuprofen domains. Basic additives formed both soluble and insoluble salts with the ibuprofen depending on the pH modifier added. Tablets consisting of hydroxypropyl methylcellulose, ibuprofen, and an acidic or basic additive were studied. FTIR imaging in ATR mode was used for analysis of water ingress into the tablet and the presence, distribution, and chemical state of the drug. The FTIR imaging data showed distinct changes in the dissolution of crystalline ibuprofen between the formulations with different pH modifiers. In the basic formulations, FTIR imaging identified the formation of salts. The sodium salt formed was highly soluble and enhanced dissolution, whereas the calcium salt was highly insoluble and slowed the dissolution. FTIR imaging has produced important data concerning the internal matrix dissolution performance. © 2011 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4745–4755, 2011