Ipratropium bromide, a bronchodilator, is used as an inhalation solution. Commercial ipratropium bromide solution products are packaged in low-density polyethylene (LDPE) vials, through which semivolatile compounds are reported to migrate. In this article, a specific reversed phase-high performance liquid chromatographic method to assay vanillin, a semivolatile compound, in ipratropium bromide solution is described. The method was validated for a concentration range for vanillin from 30 ng/mL to 1,600 ng/mL. Migration of vanillin was assessed in two commercial preparations, ATROVENT (ipratropium bromide) Inhalation Solution packaged in a secondary foil pouch and a generic ipratropium bromide inhalation solution packaged in a carton. Levels of vanillin detected in ATROVENT after 6 months of storage at 40 degrees C and 75% RH were below the limit of detection (11 ng/mL). Significant migration of vanillin was observed after 1 month in the generic product and reached 165 ng/mL to 999 ng/mL in three months under the same storage conditions. It is concluded that this method can be readily used to measure vanillin in commercial preparations of ipratropium bromide inhalation solution. The results strongly indicate that a protective secondary packaging material is critical in preventing migration of semivolatile compounds. This study result is in agreement with the FDA's recommendation to consider even the secondary packaging components as potential sources of contamination and the use of an overwrap (typically aluminum foil) to decrease the overall permeability.