A late eluting impurity peak was observed in the size exclusion chromatography (SEC) analysis of stability samples of a syringe formulated drug product.  The impurity was suspected to be a low molecular weight leachable since it elutes in the chromatographic space beyond the effective SEC range where the size based retention mechanism becomes dominated by typical analyte stationary phase interactions.  It was observed that the impurity is readily extracted from the syringe stoppers utilizing a mixture of water with an organic solvent (methanol or acetonitrile).  The extracted solution was subjected to LC-MS analysis for structural characterization of the impurity.  Following the collection and interpretation of the LC-MS data, a structure proposal was still not clear.  In order to gain additional structural information, LC-SPE-NMR was utilized for the isolation and structural elucidation of the unknown leachable from the syringe stopper extract solution.  Based on the NMR data, the leachable was identified as 2,6-di-tert-butyl-4-hydroxy-4-methylcyclohexa-2,5-dienone (BHT-O).  The absolute identification of the leachable was confirmed by comparison of the extracted impurity with a purchased reference standard of BHT-O.  Challenges associated with the unexpected behavior of BHT-O in the mass spectrometer will be presented along with data from the LC-SPE-NMR structural elucidation.

Structural elucidation of a leachable impurity observed in a syringe formulated drug product stability sample

248th National Meeting (2014)

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