Fluorometric liquid-chromatographic determination of serum cortisol

We describe a sensitive and specific liquid-chromatographic assay for serum cortisol, exploiting acid-induced fluorescence. Each analysis requires only 50 microL of serum, and chromatography is complete in 7 min. Analytical recovery of cortisol added to serum ranged from 90 to 105% and between-run precision (CV) from 6 to 8%. The lower limit of detection for cortisol is 10 micrograms/L, and linearity extends to 1600 micrograms/L. Numerous steroids and drugs tested did not interfere.