Determination of equilibrium constant of the isotropic disproportion between water and heavy water using near infrared spectroscopy

Abstract

We have proposed near-infrared (NIR) spectroscopy for the determination of the equilibrium constant (K) of H2O/D2O disproportionation. When quantitative determination of the components in H2O/D2O disproportionation using NIR spectroscopy is executed with the help of chemometrics, the result would be linear and accurate if correct equilibrium concentration of a component is used as reference concentration. An equilibrium constant providing the best accuracy as well as linear relationship in quantitative analysis can be regarded as the equilibrium constant of a given reaction. Consequently, as a feed-back fashion, we can determine the K of H2O/D2O disproportionation through the examination of the quantitative performances using the reference concentrations calculated from different K values, arbitrarily varied to cover wide range. By simultaneously evaluating errors (SECV; standard error of cross validation) and regression coefficients from PCR, the equilibrium constant was determined as 3.72 ± 0.35 and this result was consistent with those from previous publications.