How to obtain true and accurate rate-values.

In metabolic flux calculations, the uptake and secretion rates (for substrate, O(2), CO(2), growth, (by)-products) are essential to arrive at correct calculated fluxes. Surprisingly, a lot of research has been published on the methods of flux calculations, but much less attention has been spent on the methods to obtain accurate and true uptake and secretion rates which are used as input. Therefore, this contribution focuses on.