Determination of estrogens in human serum using a novel chemical derivatization–assisted liquid chromatography‐electrospray ionization‐tandem mass spectrometry method

Rationale Assessing estrogen concentrations in biological systems can provide valuable information on physiological processes, which is crucial for the early diagnosis of many diseases. Because estrogens are present in the human body in low concentrations and in a wide dynamic range, analytical methods with high sensitivity and specificity are required for their determination in complex biological matrices. Methods To discover an appropriate derivatization reagent for estrogen mass spectrometry (MS) analysis, we compared five sulfonyl chloride derivatization reagents, namely 3‐methyl‐8‐quinolinesulfonyl chloride (MQSCl) and 8‐quinolinesulfonyl chloride (QSCl), 1‐methyl‐1 H ‐pyrazole‐4‐sulfonyl chloride, 1,2‐methyl‐imidazole‐5‐sulfonyl chloride, and dansyl chloride. By selecting the derivatization reagent with the best performance, we developed and validated a novel chemical derivatization–assisted‐liquid chromatography‐electrospray ionization‐tandem mass spectrometry (CD‐LC‐ESI‐MS/MS) method to simultaneously determine the concentrations of estrone, estradiol, and estriol (E1, E2, and E3) in human serum. Results It was found that among the five investigated reagents, MQSCl‐derivatized estrogens presented the highest sensitivity using LC‐ESI‐MS/MS. Based on this discovery, MQSCl was chosen to derivatize the analyzed estrogens to assist LC‐ESI‐MS/MS analysis. The limit of quantification of E1, E2, and E3 was measured as 2.7, 4.6, and 5.1 pg/mL, respectively. Inter‐ and intra‐day precision, expressed as the coefficient of variation, was shown to be lower than 13.2% for all concentrations. The mean recovery was 72.4% overall, with good reproducibility at low, medium, and high concentrations in the calibration range. Conclusions The developed method was successfully applied to the quantitative determination of estrogens in clinical human serum from pediatric and adult women, demonstrating the suitability of estrogen analysis in the biological matrix at low concentration (pg/mL).