Excipients are pharmacologically inactive substances used as carrier for the active pharmaceutical ingredient (API). A significant amount (30-80% solid) of polymeric excipients such as hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), and povidone are generally used. Those excipients have very large molecular (MW) which is not suitable for the commonly used drug QC method by LC-MS. Whereas LC-IR is feasible of characterizing any polymeric excipients in all drug forms.
OHpak SB-806M HQ was used to separate excipients and API based on their sizes. Then size-separated components were detected by IR which provides compositional fingerprinting information. The method is useful in the areas such as drug production quality control, drug deformulation, and/or counterfeit drug testing.


Figure 1: Analysis of a test drug sample.
Result shows there were cellulose (Peak A; MW=~485K Da) and two different MW Povidones
(Peak A; MW=~485K Da and Peak B; MW=~49K Da) used as excipients in the tested drug sample.


Figure 2: Analysis of HPC sample.
Result shows there were HPC excipient having two different MW distributions (MW information not available).

Sample :
Cellulose
Povidone
Hydroxypropyl cellulose, HPC

Column       : Shodex OHpak SB-806M HQ (8.0 mm I.D. x 300 mm)
Eluent       : 1.5 % DMF/H2O
Flow rate    : 1.0 mL/min
Detector     : DiscovIR-LC™
Column temp. : 40 °C

Data provided by Dr.Ming Zhou, Spectra Analysis Instruments, Inc. www.spectra-analysis.com