Rapid Identification of Hydrogen Isotopes in Water Mixtures by FTIR Spectroscopy

A method for rapid determination of the relative concentration of hydrogen isotopes in aqueous solutions was developed based on the rapid measurement of the different molecular bending vibrations using Fourier transform infrared (FTIR) spectroscopy. Isotopic H₂O and D₂O mixtures (with D₂O concentration varying from 0%-100%) were examined in the liquid phase under different environments to estimate the stability, repeatability, and accuracy of FTIR spectroscopy as a rapid assay technique for heavy and light water mixtures. The generated results suggested a high agreeability with the simulated equilibrium constant of the water mixture (average deviation close to 1%) after considering the existence of HDO in the solution. The high sensitivity of the molecular bending motion in detecting the isotopic variations of hydrogen (approximately 0.5%) also proved the reliability of applying FTIR spectroscopy in isotopic determinations. Therefore, we suggested a relatively accurate and rapid identification method for determining the relative proportion of hydrogen isotopes in an aqueous solution by measuring and ratiating the relative peak intensity of the FTIR recorded vibrational peaks.