“…This study aims to evaluate the stability in aerosol containers of two mucolytic agents, N-acetylcysteine (300 mg/3 ml) and ambroxol (15 mg /2ml), and two corticosteroids beclomethasone dipropionate (800 μg /2ml) and budesonide (0.50 mg /2ml and 0.25 mg /2ml), after dilution with Sirmione thermal water stored in plastic ampoules, for aerosol therapy. A large number of analytical methods for the determination and quantifi cation of N-acetylcysteine [11,12], ambroxol [13,14], budesonide [15] and beclomethasone dipropionate [16,17] in pharmaceutical preparations have been developed. However, in spite of the structural diversity and different chemical-physical properties of these drugs (Figure 1), mainly due to the presence of excipients (sodium edetate, polysorbate 80, polysorbate 20, and sorbitan laurate) that can interfere with the separation process, no method was found for their simultaneous analysis.…”