Used as a stable isotope-labeled internal standard in mass spectrometry-based bioanalytical assays for the quantification of N-Acetyl Desethyl Chloroquine in biological samples. Its primary application lies in pharmacokinetic and metabolic studies, where it helps ensure accurate measurement of the analyte by compensating for matrix effects and instrument variability. Commonly employed in drug development and clinical research involving chloroquine or its derivatives, particularly in studies related to malaria and autoimmune diseases.