Yuewu Xiao is a Senior Research Scientist at EMD Millipore. As the technical leader in the Spectroscopy lab, his responsibility is to apply various spectroscopic techniques to support R&D projects, to solve manufacturing issues, and to handle complaints from external customers including all top ten pharmaceutical and biopharmaceutical companies. He received his Ph.D. degree in chemistry from Syracuse University, and M.S. and B.S. degrees in chemistry from Nanjing University, China.


Monoclonal antibody (mAb) purification usually employs a template process, which often includes cation exchange chromatography after the Protein A step. The mAb eluate from the Protein A column is at pH ~ 3-4, and should be adjusted to have the optimal pH (~ 4-6) and conductivity (~ 0-100 mS/cm) for the subsequent cation exchange chromatography. To obtain the optimized conditions for a mAb and a cation exchanger, the most common trial and error approach is to analyze the loading and elution profiles of the mAb in solution state. In this presentation, a monoclonal antibody (EMD Millipore mAb04) was loaded onto a strong cation exchanger (Fractogel EMD SO3 (M)) at pH 5 or 4 with a conductivity of 10 mS/cm or 2 mS/cm. Confocal Raman spectroscopy was applied, for the first time, to measure protein distribution and conformational changes in chromatographic particles. Both depend on the loading pH and conductivity. This approach therefore can help the researcher to understand, on a very small scale using a single chromatography bead, how and why the loading conditions will affect mAb purification by the cation exchanger at full scale.