The European and United States Pharmacopeias require the characterization and quantification of host cell proteins (HCPs) contaminating biological products, as these proteins pose a potential risk to clinical safety and product stability. The Enzyme-linked ImmunoSorbent Assay (ELISA) is currently the reference method for quantifying total HCPs, although it does not guarantee accurate and comprehensive detection of all HCPs. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is an alternative and orthogonal technique to ELISA, offering higher sensitivity and a broader dynamic range. In this study, we demonstrate the unmatched advantages of the Scout-triggered MRM targeted acquisition method for analyzing a 240-peptide-plex assay (720 transitions) targeting 97 HCPs in various crude or purified industrial bioproduct matrices derived from Chinese hamster ovary (CHO) cell cultures. Beyond its high multiplexing capability, the main advantage of Scout-triggered MRM, compared to conventional retention time-based methods, lies in its robustness against peptide retention time shifts across different pharmaceutical products. This method allowed us to achieve a dynamic range covering six orders of magnitude, quantifying HCPs down to 2.9 ppm.