Method development for quantitative monitoring of monoclonal antibodies in upstream cell‐culture process samples with limited sample preparation – An evaluation of various capillary coatings

Monoclonal antibodies (mAbs) have become an important class of biopharmaceuticals used for the treatment of various diseases. Their quantification during the manufacturing process is important. In this work, a capillary zone electrophoresis (CZE) method was developed for the monitoring of the mAb concentration during cell‐culture processes. CZE method development rules are outlined, particularly discussing various capillary coatings, such as a neutral covalent polyvinyl alcohol coating, a dynamic successive multiple ionic‐polymer coating, and dynamic coatings using background electrolyte additives such as triethanolamine (T‐EthA) and triethylamine. The dynamic T‐EthA coating resulted in most stable electro‐osmotic flows and most efficient peak shapes. The method is validated over the range 0.1–10 mg/ml, with a linear range of 0.08–1.3 mg/ml and an extended range of 1–10 mg/ml by diluting samples in the latter concentration range 10‐fold in water. The intraday precision and accuracy were 2%–12% and 88%–107%, respectively, and inter‐day precision and accuracy were 4%–9% and 93%–104%, respectively. The precision and accuracy of the lowest concentration level (0.08 mg/ml) were slightly worse and still well in scope for monitoring purposes. The presented method proved applicable for analysing in‐process cell‐culture samples from different cell‐culture processes and is possibly well suited as platform method.