Amisulpride-d5, a deuterated form of amisulpride, is primarily used in research and development as an internal standard in analytical chemistry. Its application is crucial in mass spectrometry and high-performance liquid chromatography (HPLC) for the accurate quantification of amisulpride in biological samples. By incorporating deuterium atoms, it provides a stable reference that closely mimics the behavior of the parent compound, ensuring precise and reliable measurements. This is particularly valuable in pharmacokinetic studies, therapeutic drug monitoring, and forensic toxicology, where detecting and quantifying amisulpride in complex matrices like blood, plasma, or urine is essential. Additionally, it aids in the development and validation of analytical methods, contributing to improved accuracy and reproducibility in clinical and pharmaceutical research.