Therefore, the course of a hydrogenation reaction in which NAD(P)H is converted to NAD(P) + can be observed in real time if it is run in a quartz cuvette in a UV spectrometer. By observing the decreas...Therefore, the course of a hydrogenation reaction in which NAD(P)H is converted to NAD(P) + can be observed in real time if it is run in a quartz cuvette in a UV spectrometer. By observing the decrease in absorbance at 340 nm, the researcher can calculate how many moles of NAD(P)H has been oxidized at any given time point, and this number is equal to the number of moles of organic substrate that has been reduced.