Carbon isotope ratio analysis of steroids by high-temperature liquid chromatography-isotope ratio mass spectrometry.
Generally, compound-specific isotope analysis of steroids is carried out by gas chromatography combined with isotope ratio mass spectrometry. Thus, a derivatization of the steroids prior to the measurement is compulsory, and a correction of the isotopic data is often necessary. To overcome this limitation, we present a new approach of high-temperature liquid chromatography coupled with photodiode array detection and isotope ratio mass spectrometry (HT-LC/PDA/IRMS) for the carbon isotope ratio analysis of unconjugated steroids. A steroid mixture containing 19-norandrosterone, testosterone, epitestosterone, androsterone, and 5β-pregnane-3α,17α,20α-triol was fully separated on a C4 column under high-temperature elution with water as the sole eluent. The accuracy for isotope analysis (±0.5 ‰) was around 20 μg g(-1) for testosterone, epitestosterone (79 ng steroid absolute on column), and 30 μg g(-1) for 19-norandrosterone, androsterone, and 5β-pregnane-3α,17α,20α-triol (119 ng steroid absolute on column). The applicability of the method was tested by measuring a pharmaceutical gel containing testosterone. With this work, the scope of LC/IRMS applications has been extended to nonpolar compounds.
Instrumental Analytical Chemistry, University Duisburg-Essen , Universitätsstr. 5, 45141 Essen, Germany.
Lijun
L
Zhang
Mario
M
Thevis
Thomas
T
Piper
Maik A
MA
Jochmann
J Benjamin
JB
Wolbert
Dorothea M
DM
Kujawinski
Steffen
S
Wiese
Thorsten
T
Teutenberg
Torsten C
TC
Schmidt