Date of this Version
J Chromatogr B Analyt Technol Biomed Life Sci. 2008 July 15; 870(2): 233–240
A fast and sensitive LC-ESI-MS method is described for the comparative quantification of 16 estrogen metabolites based on the derivatization of estrogens with a novel derivatizing reagent, Nmethyl- nicotinic acid N-hydroxysuccinimide ester (C1-NA-NHS). The process introduces a quaternary amine to the analytes, making the analytes permanently charged regardless of the pH of the HPLC mobile phase. This quaternization resulted in a highly efficient separation of 16 estrogen metabolites in 7 minutes at a detection level below 1 ng/mL. By using a deuterated derivatizing reagent (C1-d3-NA-NHS), a complete set of deuterated standards was utilized and used as internal standards in a comparative quantification and recovery study, demonstrating acceptable results over a wide concentration range. A pooled breast cancer serum sample was analyzed using the described method, and 15 estrogens were detected in the range of 80 – 530 pg/mL.