Use of ferric thiocyanate derivatization for quantification of polysorbate 80 in high concentration protein formulations.

Quantitation of polysorbate 80 in high protein formulation using solid-phase extraction (SPE) followed by derivatization with cobalt thiocyanate and UV measurement of the complex at 620 nm resulted in lower recovery of polysorbate 80. Dilution of protein samples with water improved the recovery of polysorbate, however, it compromised the sensitivity of the method when cobalt thiocyanate was used for derivatization. The presented work discusses an evaluation of alternative approaches for increasing the sensitivity of the quantitation method for polysorbate using ferric thiocyanate and molybdenum thiocyanate.

Assessment of stable isotope incorporation into recombinant proteins.

Stable isotope labeling combined with mass spectrometry has been widely used in a diverse set of applications in the biochemistry and biomedical fields. When stable isotope-labeled proteins are produced via metabolic labeling of cell culture, a comprehensive assessment of the labeling pattern is imperative. In this study, we present a set of mass spectrometry-based bioanalytical tools developed for quantitatively tracing the levels of the stable isotopes incorporated into the recombinant proteins (monoclonal antibodies and Fc fusion proteins expressed in different host systems) that include total mass analysis, peptide mapping analysis, and amino acid analysis.