Insulin was the first recombinant pharmaceutical produced. Currently, one of the critical quality control attributes of therapeutic insulin in the US and European Pharmacopoeia (USP and EP) monograph is the level of covalent high molecular weight (HMW) insulin as determined by HPLC size-exclusion chromatography.
For the analysis of biotherapeutics, size-exclusion and ion-exchange chromatography are typically conducted under native separation conditions, requiring high ionic strength, 100% aqueous eluents.