Determination of Deuterium Isotopic Abundance in Lithium Aluminum Deuteride by Nuclear Magnetic Resonance Spectroscopy

Addressing the technical bottleneck of directly determining deuterium isotopic abundance in lithium aluminum deuteride (LiAlD₄) due to its inorganic nature and high reactivity, this study developed a novel detection strategy based on isotope coded derivatization coupled with Nuclear Magnetic Resonance spectroscopy. Deuterium atoms were directionally transferred from the inorganic matrix to an organic product via the reaction of LiAlD₄ with benzophenone to synthesize deuterated benzhydrol. Optimized derivatization conditions were established as a molar reactant ratio of 1:2 and a reaction time of 1 hour. Crucially, non-deuterated reagents (diethyl ether/water/sulfuric acid) could substitute deuterated counterparts without compromising abundance accuracy. For NMR detection, methanol-D₄ was employed as the solvent, with parameters set to a relaxation delay (D1) of 50 s, a pulse angle of 90 ℃, and 32 scans. The deuterium isotopic abundance was calculated from the integration ratio of the deuterium-labeled methylene signal to the reference aromatic proton signals. Method validation demonstrated a deviation of only 0.1 atom%D between the measured value (99.2 atom%D) and the certified value of a standard (99.1 atom%D), with a relative standard deviation (RSD) of ＜0.1% (n=6). Analysis of actual samples from three manufacturers showed deviations from certificate values all below 0.2 atom%D, confirming the method's accuracy, stability, and broad applicability, This work provides a reliable technical foundation for deuterated drug development and quality control of deuterium sources.