Steroid isotopic standards for gas chromatography-combustion isotope ratio mass spectrometry (GCC-IRMS)
Related Experiment Video
Updated: Jun 28, 2026

Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers
Published on: April 17, 2018
Ying Zhang1, Herbert J Tobias, J Thomas Brenna
1Cornell University, Division of Nutritional Sciences, Savage Hall, Ithaca, NY 14853, United States.
Abstract:
Carbon isotope ratio (CIR) analysis of urinary steroids using gas chromatography-combustion isotope ratio mass spectrometry (GCC-IRMS) is a recognized test to detect illicit doping with synthetic testosterone. There are currently no universally used steroid isotopic standards (SIS). We adapted a protocol to prepare isotopically uniform steroids for use as a calibrant in GCC-IRMS that can be analyzed under the same conditions as used for steroids extracted from urine. Two separate SIS containing a mixture of steroids were created and coded CU/USADA 33-1 and CU/USADA 34-1, containing acetates and native steroids, respectively. CU/USADA 33-1 contains 5alpha-androstan-3beta-ol acetate (5alpha-A-AC), 5alpha-androstan-3alpha-ol-17-one acetate (androsterone acetate, A-AC), 5beta-androstan-3alpha-ol-11, 17-dione acetate (11-ketoetiocholanolone acetate, 11k-AC) and 5alpha-cholestane (Cne). CU/USADA 34-1 contains 5beta-androstan-3alpha-ol-17-one (etiocholanolone, E), 5alpha-androstan-3alpha-ol-17-one (androsterone, A), and 5beta-pregnane-3alpha, 20alpha-diol (5betaP). Each mixture was prepared and dispensed into a set of about 100 ampoules using a protocol carefully designed to minimize isotopic fractionation and contamination. A natural gas reference material, NIST RM 8559, traceable to the international standard Vienna PeeDee Belemnite (VPDB) was used to calibrate the SIS. Absolute delta(13)C(VPDB) and Deltadelta(13)C(VPDB) values from randomly selected ampoules from both SIS indicate uniformity of steroid isotopic composition within measurement reproducibility, SD(delta(13)C)<0.2 per thousand. This procedure for creation of isotopic steroid mixtures results in consistent standards with isotope ratios traceable to the relevant international reference material.
Related Concept Videos
Gas Chromatography–Mass Spectrometry (GC–MS)
A gas chromatograph consists of a long, narrow capillary column with a polysiloxane coating on the inner wall. The coating...
Mass Spectrometry: Isotope Effect
Chemical Ionization (CI) Mass Spectrometry
Gas Chromatography: Introduction
In GC, a sample is vaporized and mixed with an inert carrier gas (the mobile phase), which transports it through a column.
High-Resolution Mass Spectrometry (HRMS)
Inductively Coupled Plasma–Mass Spectrometry (ICP–MS): Overview
