Determination of cortisol in human plasma by using immunoaffinity solid-phase microextraction based on carbon fibers immobilizing antibody

Cortisol is quantitatively the major glucocorticoid class of steroid hormone involved in the regulation of metabolic homeostasis. Since it is widely used as a biomarker in the diagnosis of human diseases such as Addison’s disease and Cushing’s syndrome, accurate cortisol quantification is still a challenging task. Here, a novel immunoaffinity solid-phase microextraction method, based on carbon fibers immobilized with antibody, was developed for the determination of cortisol coupled with liquid chromatography-tandem mass spectrometry. The limit of detection and quantification of the proposed method were found to be 0.102 and 0.340 ng/mL, respectively. The linearity was satisfactory with the determination coefficient to R² = 0.9996. The relative recoveries were in the range of 98.03 to 113.16% with relative standard deviations ≤ 6.52% (n = 3). This method was successfully applied to the determination of cortisol in human plasma.