Measurement of urinary free cortisol by stable isotope dilution mass spectrometry using a new cortisol derivative.
The reaction of the bismethylenedioxy derivative of cortisol (cortisol-BMD) with heptafluorobutyric anhydride to give the corresponding 3,5-dienol heptafluorobutyrate (cortisol-BMD-HFB) has been shown to proceed with dehydration. Acid-promoted dehydration of either cortisol-BMD or cortisol-BMD-HFB, or concurrent dehydration of both, is the proposed reaction mechanism leading to a trienol heptafluorobutyrate, whose chromatographic properties and mass spectral data are consistent with the additional double bond in the C9-C11 position. Forming the 3,5-dienol heptafluorobutyrate of cortisol-BMD in benzene rather than acetone gave a compound whose chromatographic properties and mass spectral data were different to that of the 3,5,9(11)-trienol heptafluorobutyrate but consistent with that of a cortisol-BMD-HFB. The mass fragmentometry of this new cortisol derivative was found to be more suited to the technique of isotope dilution mass spectrometry than the 3,5,9(11)-trienol heptafluorobutyrate, and thus was applied to our intended goal of measuring urinary free cortisol by gas chromatography-mass spectrometry. An efficient and convenient solid-phase extraction technique is employed in our assay to isolate cortisol from 5 ml of urine.
Ray Williams Clinical Mass Spectrometry Facility, Department of Chemical Pathology, St. Vincent's Hospital, Darlinghurst, Sydney, NSW, Australia.
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Varelis
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Smythe
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D
Hodgson
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Lazarus
D005466:Fluorocarbons / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000652:urine*; D011865:Radioisotope Dilution Technique
D005466:Fluorocarbons; C007924:heptafluorobutyric anhydride; D006854:Hydrocortisone