Why do I get different values of absorbance for cell culture (cell growth) measurements?
Thermo Scientific: Even though the measurement is often referred to as an A600 measurement, cell growth or cell culture methods actually rely on the scattering of light by the cells to make a measurement. Because cell growth measurements are based on the scattering of light by the growing population of cells, differences in the optical configuration of the instrument have a large impact on the measured “absorbance” value. Absorbance is placed in quotation marks, here because, again, the absorbance is not measured, the scattered light appear to the instrument to be absorbed. Subtle differences in optical geometry, like the distance of the sample to the detector can have large impact on the measured “absorbance.” The good news is that for all instruments the difference in measured “absorbance” or optical density (OD) between instruments is linear. This means that the growth curves recorded on different instruments are identical in shape, but differ in magnitude. Therefore, differences in
