We use XPS to quantify the amount of an API (indomethacin) and two excipients (sodium carboxymethylcellulose and Poloxamer 407) present on the outer surface of individual particles. Analyses were done both in aggregate, to provide a snapshot of the average surface composition, as well as on individual particles- to assess surface chemical uniformity.
Understanding the surface concentration of various components in pharmaceutical powders is critical for controlling performance parameters such as solubility, dissolution, stability, flowability, agglomeration and crystallinity.