As expected due to the application of a phosphate buffer, experimental results showed auto-oxidation of the cofactor NADH over time, as previously reported in literature. In order to model the reaction system as precisely as possible, the auto-oxidation of NADH was measured at wavelengths of λ1 = 340 nm and λ2 = 292 nm in a time range of 48 hours using a VWRTM UV-1600PC Spectrophotometer. Additionally, absorption values at λ3 = 260 nm increased analogous to NADH-oxidation during these experiments, indicating that NADH is oxidized to NAD+. In our mathematical model it is therefore assumed, that NADH auto-oxidizes to NAD+. The resulting NADH-oxidation for this system is described through a function of exponential decay as shown in equation (5):