Hiden Analytical’s HPR-40 DSA has been used to perform fast response, high precision measurements of dissolved N2 and Ar in water. The deviation of the N2, Ar concentrations from equilibrium are known to be indicative of the important biological and physical processes taking place in the marine and aquatic biological environments. The HPR-40 DSA has measured the precision (co-efficient of variance) of N2, Ar and the N2/Ar ratio as: Cv(N2) ≤ 0.26 %, Cv(Ar) ≤ 0.25 %, and Cv(N2/Ar) ≤ 0.058 % respectively. Such high-precision measurements are important, in particular, in the study of the sensitive marine biological process of denitrification: NO3– → N2.