Speaker at Global conference on Pharmaceutics and Drug Delivery Systems 2019 - Ekaterina Sobich
AbbVie Deutschland GmbH & Co. KG R&D, Germany
Title : Molecular weight characterization of sodium carboxymethyl cellulose by advance polymer chromatography


Advanced polymer chromatography (APC) is a size exclusion chromatography (SEC) designed by Waters for fast, efficient, and robust polymer characterization. The molecular weight (Mw) separation range is from 100 Da to 2 000 kDa and quick switch from one solvent to another solvent is possible. APC shows high reproducibility. By combination of columns with different pore sizes in a single column set, it is possible to adjust the molecular weight separation range for the measured polymer.This poster demonstrates the application of APC for the determination of relative molecular weight distribution (MWD) of Sodium Carboxymethylcellulose (NaCMC), a commonly used pharmaceutical excipient. NaCMC is a linear cellulose derivate functionalized with the sodium acetate groups which make the polymer soluble in water. Depending on the cellulose material source and the degree of the substitution, the NaCMC can vary in MWD which can cause variability in the properties like viscosity, thickening, emulsifying, and suspending-ability in solution.
    Firstly, we investigated the elution behavior of NaCMC and Pullulan standards in several buffers and choose the best eluent for SEC separation on the APC. Secondly, the relative MWD of the NaCMC samples was determined and compared to their viscosity data. Different grades of NaCMC samples were obtained from two vendors. For the calibration for the relative MWD determination the narrow Pullulan standards (peak molecular weight in range 180 – 1 200 000 Da) were chosen. Pullulan as calibration standard was used because its chemical structure is similar to NaCMC, and also high molecular weight Pullulan standards are commercially available. The SEC separations were run on the APC (Waters corp.) equipped with IR-detector.
     NaCMC is a polyelectrolyte and showed different elution behavior dependent on the mobile phase. After testing several eluents on the APC column set, it was found that NaNO3/NaH2PO4 pH=7 was the most suitable buffer for the separation. The NaCMC samples eluted as a broad peak with a main peak in the high molecular weight range and a tail which combined the middle and low molecular weight range.  It is shown that APC is a very fast, reproducible, and powerful tool for the relative MWD determination of the derivates of cellulosic polymers. Variations in MWD of the NaCMC samples could be easily detected with the APC and the results compared with viscosity data.
All authors are employees of AbbVie and may own AbbVie stock. AbbVie sponsored and funded the study; contributed to the design; participated in the collection, analysis, and interpretation of data, and in writing, reviewing, and approval of the final publication.


Ekaterina Sobich studied Chemical Biology at the Karlsruhe Institute of Technology, Germany and graduated as Master of Science in 2015. She then joined GGPD NCE Formulation Sciences at AbbVie Deutschland GmbH & Co. KG and has focused on the implementation and application of Advanced Polymer Chromatography for the researches on the polymers and pharmaceutical formulations.