Phosphoric acid-d3 solution is primarily used in nuclear magnetic resonance (NMR) spectroscopy as a deuterated solvent or reference standard. Its deuterium content allows for precise analysis of molecular structures, particularly in organic and inorganic chemistry research. The solution is also employed in isotope labeling studies to track chemical reactions and metabolic pathways. Additionally, it serves as a pH adjuster in specialized laboratory experiments where deuterium substitution is required to avoid interference from hydrogen signals. Its application extends to the synthesis of deuterated compounds, which are essential in various fields, including pharmaceuticals and material science.