The Measurements and Instrumentation

Stable isotope ratios are measured by combustion and mass spectrometric analyses of either bulk phases or specific compounds. Bulk phases are typically analyzed by either offline combustion followed by dual-inlet mass spectrometry or by online combustion coupled with isotope-ratio-monitoring/mass spectrometry (irmMS). Specific compounds are analyzed by either gas chromatography coupled with irmMS (irmGCMS) or by liquid chromatography coupled with irmMS (irmLCMS), depending on the chromatographic properties of the analytes. Jasper (1999; see “MIT Articles”) reviews nine major points regarding the properties and uses of stable isotopes in the pharmaceutical industry, including the suggestion of Nature’s Fingerprint® and Isotopic Pedigree® Authentication of Active Pharmaceutical Ingredients (APIs) and drug products.

Elemental Analyzer-MS (EA-MS)