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Quantitative analysis of cortisol and 6β‐hydroxycortisol in urine by fully automated SPE and ultra‐performance LC coupled with electrospray and atmospheric pressure chemical ionization (ESCi)‐TOF‐MS

An ultra‐performance LC TOF MS method for quantitative analysis of cortisol and 6β‐hydroxycortisol in urine was developed. The method was used for determination of the ratio between 6β‐hydroxycortisol and cortisol in urine received from autopsy cases and living persons as a measure of cytochrome P450 3A enzyme activity. Urine samples (0.25 mL) were extracted with an in‐house developed fully automated 96‐well SPE system. The compounds were quantified using a Waters ACQUITY UPLC system coupled to a Waters SYNAPT G2. The MS sensitivity was optimized by using negative ionization in sensitivity mode (resolution >10 000 full‐width at half‐maximum), and further optimized by using the enhanced duty cycle around the 410 m/z. ESCi (simultaneous electrospray and atmospheric pressure chemical ionization) mode was used to compensate for the matrix effects of postmortem urine. Finally, the SYNAPT G2 was tested as a quantitative instrument. The developed method has a measurement range from 2.5–300 ng/mL for cortisol to 10–1200 ng/mL for 6β‐hydroxycortisol. Mean overall process efficiencies were 29.4 and 23.0% for cortisol and 6β‐hydroxycortisol, respectively. In 20 forensic reference cases, the range of the 6β‐hydroxycortisol/cortisol ratio was 0.29–14.2 with a median of 3.04.

Authors:   Lotte M. Lang, Petur W. Dalsgaard, Kristian Linnet
Journal:   Journal of Separation Science
Year:   2012
Pages:   n/a
DOI:   10.1002/jssc.201200736
Publication date:   15-Dec-2012
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