Ampicillin-d5, a deuterated form of ampicillin, is primarily used in research and analytical applications as an internal standard in mass spectrometry. Its stable isotopic labeling allows for precise quantification and tracking of ampicillin in biological samples, ensuring accurate pharmacokinetic and metabolic studies. This compound is particularly valuable in drug development and biomedical research, where understanding the distribution, metabolism, and excretion of ampicillin is critical. Additionally, it aids in differentiating between endogenous and exogenous substances in complex matrices, enhancing the reliability of analytical results.