Solid State NMR of Drugs: Soluble Aspirin

Abstract Natural abundance 13C NMR spectra of a soluble aspirin and model mixtures of acetylsalicylic acid with buffering components have been recorded in the solid state by using the combined techniques of cross polarization, high-power decoupling and magic-angle spinning. The solid-state spectrum of the soluble aspirin tablet showed more resonances than the solution spectrum. These multiplicities were originated in the buffer mixture containing citric and tartaric acid, as well as their salts. Solid-state 13C NMR was therefore found to provide information that is lost in the solution spectrum due to the fast proton exchange between the organic acids and their conjugated salts.