Stable isotopic characterization of active pharmaceutical ingredients

Area of Science:

• Analytical Chemistry
• Pharmaceutical Science

Background:

• Stable isotope analysis provides a unique
• fingerprint
• for materials.
• Active Pharmaceutical Ingredients (APIs) require robust methods for origin verification to ensure quality and prevent counterfeiting.

Purpose of the Study:

• To evaluate the efficacy of stable isotope ratio analysis in determining the provenance of four different APIs.
• To assess the specificity and range of isotopic variations across different manufacturers and batches.

Main Methods:

• Stable isotope ratios (¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O, D/H) were measured for four APIs: tropicamide, hydrocortisone, quinine HCl, and tryptophan.
• Elemental Analyzer/Isotope Ratio Mass Spectrometry (EA/IRMS) and Thermal Conversion-EA/IRMS (TCEA/IRMS) were employed.
• Isotopic results were reported using delta notation relative to international standards.

Main Results:

• Significant variations in isotopic ratios (delta values) were observed across the tested APIs.
• Tryptophan samples from different manufacturers exhibited the widest isotopic ranges and highest specificity (1:19.6 x 10⁶).
• Tropicamide samples from a single batch and manufacturer showed the narrowest ranges and lowest specificity (1:30.9).
• Bivariate plots, especially delta D versus delta ¹⁸O, clearly distinguished the isotopic provenance of the API suites.

Conclusions:

• Stable isotope characterization is a powerful tool for verifying the provenance of APIs.
• The method demonstrates high specificity, capable of differentiating between samples from various sources.
• Isotopic fingerprinting enhances pharmaceutical supply chain security and quality control.