A dataset of theoretical concentrations and ATR-FTIR spectra for quantitative analysis of water isotopologues (H₂O, HDO, D₂O)

BackgroundThe accurate molecular-level quantification of water isotopologues (H2O, HDO, and D2O) remains a significant analytical challenge in fields such as nuclear energy and materials science. Current standardized methods, including the Chinese National Standard GB/T 44647―2024, are limited to measuring total deuterium content using transmission-mode Fourier Transform Infrared Spectroscopy (FTIR) and cannot differentiate between HDO and D2O molecules. This inability to distinguish individual species restricts advanced applications in heavy water reactor monitoring and deuterated material analysis. Although Attenuated Total Reflection-FTIR (ATR-FTIR) offers potential for in-situ and rapid analysis, a systematic methodology and public benchmark dataset for molecular-specific quantification are still lacking.PurposeThis study aims to develop a robust quantitative method using ATR-FTIR spectroscopy to simultaneously discriminate and quantify H2O, HDO, and D2O molecules in heavy water samples.MethodsA series of heavy water samples with varying initial D2O concentrations were prepared as the research subjects. Spectra were collected using an ATR-FTIR spectrometer equipped with a diamond crystal under ambient temperature and constant pressure application to ensure optical contact and reproducibility. Then, three characteristic infrared absorption peaks, i.e., the H-O-H bending vibration (δ(H-O-H)) at about 1 640 cm-1 integrated to quantify H2O, the D-O-D bending vibration (δ(D-O-D)) at about 1 200 cm-1 used for D2O quantification, and the O-D stretching vibration (ν(O-D)) at about 2 500 cm-1 applied to determining the total O-D bond concentration, were selected for quantitative analysis. Finally, the HDO concentration was indirectly calculated using the stoichiometric relation, and each sample was measured in triplicate to evaluate repeatability.ResultsMeasured results show that this method demonstrates high precision, with all peak area measurements exhibiting a relative standard deviation (RSD) of less than 7% across five concentration levels, and excellent linearity observed in the calibration curves for all three species, with coefficients of determination (R2) exceeding 0.99. In blind testing, the deviation for D2O quantification is +4.0%, and that for O-D bonds (directly related to HDO) is +3.3%. A larger deviation of -8.6% for quantification of H2O may primarily be caused by interference from environmental moisture adsorption.ConclusionsA novel, reliable, and practical ATR-FTIR-based method established in this study for the simultaneous quantification of H2O, HDO, and D2O, effectively overcomes the limitations of existing standards. The public release of the methodology and dataset provides a critical benchmark for future development of molecular-specific isotope analysis tools. These findings offer a valuable technical solution for real-time monitoring in nuclear reactors and precision detection in deuterated material research, with further improvements in H2O accuracy expected through sample isolation techniques such as vacuum application.