Improved liquid-chromatographic method for determination of serum cortisol

Area of Science:

• Biochemistry
• Analytical Chemistry
• Endocrinology

Background:

• Cortisol measurement is crucial for diagnosing various endocrine disorders.
• Accurate and sensitive quantification of cortisol in biological samples is essential.
• Existing methods may have limitations in specificity or efficiency.

Purpose of the Study:

• To develop and validate a specific and precise liquid chromatography (LC) method for cortisol quantification.
• To establish a reliable assay for measuring cortisol concentrations in human serum or plasma.
• To assess the method's sensitivity, accuracy, and potential interferences.

Main Methods:

• Cortisol extraction from 1 mL serum/plasma with an internal standard (equilenin).
• Isocratic reversed-phase LC analysis using acetonitrile/phosphate buffer mobile phase.
• Detection of cortisol by UV absorption at 254 nm and quantification via peak height.

Main Results:

• The method provides accurate cortisol measurements with analytical recoveries exceeding 95%.
• High day-to-day precision was achieved, with coefficients of variation between 4% and 7%.
• The assay demonstrated high sensitivity (5 µg/L) and a rapid analysis time (≤15 min).

Conclusions:

• The described LC method is specific, precise, and sensitive for measuring serum or plasma cortisol.
• The assay is suitable for routine clinical use, offering reliable cortisol quantification.
• Potential interference from cortisone, prednisone, and prednisolone should be considered.