Measuring deuterium concentration in water

Deuterium is a heavy nonradioactive isotope of hydrogen, present in ocean water at a concentration of around 150 parts per million (ppm). In terrestrial nature, deuterium content in water varies by at least a factor of two, while in industry and research, the whole range of deuterium concentrations is employed. Water with altered deuterium content is currently of increasing interest in biology and medicine. Therefore, accurate measurements of deuterium content in water are an important problem. Historically, such measurements have relied on densitometry and mass spectrometry. More recently, alternative techniques emerged, such as Fourier Transform Infrared (FTIR) spectroscopy, varieties of Laser Spectroscopy (LS), Off-Axis Integrated-Cavity Laser Spectroscopy (OA-ICOS), nuclear magnetic resonance (NMR) spectroscopy, original research developments based on two-dimensional diffuse laser scattering (2D-DLS), and isotopic fractionation in metalloorganic nanotubes (MONTs). This review aims to provide brief description of the techniques currently in use for measuring deuterium content in water, evaluate their analytical performance and applicability across different contexts, and discuss the broader implications of these measurements in scientific research.