DETERMINATION OF CORTISOL AND ASSOCIATED GLUCOCORTICOIDS IN SERUM ANDURINE BY AN AUTOMATED LIQUID-CHROMATOGRAPHIC ASSAY

We describe a method for the determination of urinary free cortisol an d glucocorticoids in plasma, used in the diagnosis of adrenal disorder s, based on automated reverse-phase high-performance liquid chromatogr aphy (HPLC). The within-day and day-to-day CVs were less than 5.5 and 8.0%, respectively. The calibration curves for cortisol and 11-deoxyco rtisol were linear up to 2000 nmol/L. Cortisol concentrations as low a s 3.5 nmol/L in 1 mL of plasma or urine can be measured. Correlation o f HPLC results for 40 plasma specimens with those by radioimmunoassay showed r = 0.965. This method is sensitive and free from the interfere nce habitually encountered in immunoassays, and can thus be proposed f or research and as a potential reference method.