The CHO host cell protein elisa kit utilizes a Fed-batch CHO (K1&S) cell culture to produce HCPs, which are used for the generation of specific antibodies via sheep immunization. The CHO host cell protein ELISA kit employs a solid-phase Enzyme-linked Immunosorbent Assay (ELISA) with a double-antibody sandwich technique to detect residual CHO host cell proteins (HCPs) in the sample. Polyclonal antibody specific to CHO HCPs was employed in the assay to capture any remaining HCPs in the sample. Both the Calibration standards (or test sample) and the HRP (Horseradish Peroxidase) labeled anti-CHO HCP antibody were simultaneously added to the microtiter plate, which coated with the affinity purified capture antibody and followed by incubation and washing. Then TMB (3,3',5,5' -tetramethylbenzidine) substrate added for reaction, HRP catalyzed the oxidation of TMB by H₂O₂ to produce a blue product (maximum absorption peak at 655 nm). Then the stop solution is added to terminate the enzymatic reaction, resulting in a yellow color product (maximum absorption peak at 450 nm). The absorbance values at 450 nm wavelength were positively correlated with the HCPs concentration in the Calibration standards and the sample. The concentration of CHO HCPs in the sample can be calculated using the dose-response curve.