The concentration difference of DBCO at 8 h ∆C 8h between the control and the sample is recalculated to the number of DBCO molecules N DBCO . As DBCO and N 3 react in a 1:1 ratio, the number obtained is equal to the number of azide molecules N N 3 in the reaction mixture. Using the volume of the reaction mixture V reaction and Avogadro's number N A :