Figure 1. How well does absorbance correlate with cell density and viability measurements in batch and fed-batch cell culture? As expected in science and nature, the answer depends on a set of factors. Many people working with batch or fed-batch cell culture will reference discrete offline measures of cell activity. Total cell density (TCD), viable cell density (VCD), and percent viability can be evaluated offline using a hemocytometer and accepted trypan blue exclusion method. Cedex® and Vi-CELL™ are two examples…