During the production process several factors, including the genes of the host cell, the way of product expression and the purification steps, influence the HCP composition and abundance.[1] Several studies report that HCPs often are co-purified along with the product itself by interacting with the recombinant protein.[2] Therefore, the requirements for analytic instruments are extremely high and must be developed further to analyse the entire HCP population more thoroughly in a biopharmaceutical product.