Anal. Chem. 2004, 76, 3199-3207
Depth Profiling of 4-Acetamindophenol-Doped Poly(lactic acid) Films Using Cluster Secondary Ion Mass Spectrometry Christine M. Mahoney,* Sonya V. Roberson,† and Greg Gillen
Chemical Science and Technology Laboratory, Surface and Microanalysis Science Division, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 8371, Gaithersburg, Maryland 20899-8371
The feasibility of using cluster secondary ion mass spectrometry for depth profiling of drug delivery systems is explored. The behavior of various biodegradable polymer films under dynamic SF5+ primary ion bombardment was investigated, including several films doped with model drugs. The SF5+ depth profiles obtained from these biodegradable polymer films showed very little degradation in secondary ion signal as a function of increasing primary ion dose, and it was discovered that the characteristic ion signals for the polymers remained constant for ion doses up to ∼5 × 1015 ions/cm2. These results suggest that the polyester structure of the biodegradable polymers studied here allows for a greater ability to depth profile due to ease of main chain scission. Attempts were also made to depth profile through a series of poly(lactic acid) (PLA) films containing varying concentrations of the drug 4-acetamidophenol. The depth profiles obtained from these films show very little decrease in both the 4-acetamidophenol molecular ion and PLA fragment ion signals as a function of increasing SF5+ primary ion dose. Similar results were obtained with theophylline-doped PLA films. These results show that, in some drug delivery devices, it is possible to monitor the distribution of a drug as a function of depth by using cluster primary ion beams. In recent years, secondary ion mass spectrometry (SIMS) has proven to be a useful tool in the analysis of various drug delivery systems.1-5 With SIMS, the distribution of both drugs and excipients within a drug delivery system can potentially be determined with a high degree of spatial resolution (
