Rapid quantification of steroid patterns in human serum by on-line solid phase extraction combined with liquid chromatography-triple quadrupole linear ion trap mass spectrometry.

Background: The determination of steroids is important for the diagnosis and monitoring of endocrine diseases and infertility workup. We developed a rapid and reliable mass spectrometric method for the simultaneous quantification of steroid patterns in human serum.

Methods: An on-line solid phase extraction (SPE)-liquid chromatography-triple quadrupole linear ion trap (LC-QTrap) method utilizing atmospheric pressure chemical ionization was developed. Following protein precipitation of 100 microL serum, on-line SPE and chromatographic separation was performed for 13 steroids in 1.8 min. Analytes were confirmed by the characteristic fragment patterns.

Results: The total run time of the method was 4 min. Detection limits ranged between 0.02 microg/L (testosterone) and 9 microg/L (dehydroepiandrosterone sulfate). The method was linear up to 7000 microg/L for dehydroepiandrosterone sulfate, 500 microg/L for cortisol, 125 microg/L for 11-deoxycortisol, and 25 microg/L for aldosterone, 17-hydroxyprogesterone, progesterone, testosterone, androstenedione and beta-estradiol, respectively. Accuracy ranged between 80 and 114%. Between-day variance at three different concentration levels was <15%. Excellent correlations with immunoassays were observed for testosterone, cortisol and beta-estradiol with Pearson's correlation coefficient r=0.967, 0.963, and 0.998, respectively.

Conclusions: The novel on-line SPE-LC-MS/QTrap platform offers a very fast, reliable, and sensitive quantification of steroid patterns and fulfils the quality criteria for routine laboratory application.