Final answer:
The mass difference between rhEPO expressed in CHO and E.coli can be calculated using a mass spectrometer.
Step-by-step explanation:
The mass difference between rhEPO expressed in CHO cells and rhEPO expressed in E.coli can be determined using a mass spectrometer.
The mass spectrometer measures the ratio of the mass of different isotopes of the same element to determine the mass difference. For example, it can measure the ratio of ²H (deuterium) to ¹²C (carbon-12) in a sample.
Based on the mass spectrometer result, the mass difference between rhEPO expressed in CHO and E.coli can be calculated.