DETERMINATION OF METHOCEL A15-LV CELLULOSE ETHER IN BLENDS WITH MICROCRYSTALLINE CELLULOSE

Methocel (trademark of Dow Chemical) A15-LV cellulose ether is mixed w ith microcrystalline cellulose and used in pharmaceutical formulations to coat slow release drugs. An analysis was needed to monitor the eff iciency of the mixing of Methocel cellulose ether with the microcrysta lline cellulose. The similarities in chemical structure of Methocel ce llulose ether and cellulose made it extremely difficult for some spect roscopy techniques to distinguish between them. An extraction techniqu e followed by separation in a size-exclusion chromatography column wit h refractive index detector was developed and validated and successful ly used to monitor Methocel cellulose ether in cellulose. Also develop ed was a direct pyrolysis-capillary gas chromatography technique with flame ionization detector that generates equivalent results to the ext raction-size-exclusion chromatographic technique. Due to limitations i mposed by the requirement for small samples, the pyrolysis-GC approach is not as reproducible as the extraction-size-exclusion chromatograph ic procedure.