[Determination of Cortisol in Saliva by Liquid Chromatography Tandem Mass Spectrometry]

Objective: To establish a liquid chromatography tandem mass spectrometry method to determine the cortisol in saliva. Methods: Take 0.5 ml saliva sample into a 2 ml centrifuge tube, add excess sodium chloride and 1ml acetonitrile to it, then vortex for 3 min, centrifuge for 10 min at 15 000 r/min, and take 800 μl of the upper layer to another centrifuge tube. Finally, the sample was concentrated by a vacuum concentrator and brought to 200 μl with the initial mobile phase. Then, the sample was analyzed by liquid chromatography tandem mass spectrometry. The target compound was quantified by external standard curve method. Results: The linear range of the method was 0.02-5.00 ng/ml, r=0.999 9, the method limit of the detection was 0.002 ng/ml, the method limit of quantitative was 0.02 ng/ml, and the spiked recoveries were 89.60%-98.60%. The intra-assay precision was 1.90%-3.30%, and the inter-assay precision was 4.20%-9.00%; samples could be stored at -20 °C for at least 14 days. The determination of cortisol could not be interfered by other endogenous substances in the sample. Conclusion: The method is simple in pretreatment, high sensitivity, good reproducibility and good recovery, and it is suitable for the quantitative analysis of cortisol in saliva for normal and occupationally stressed populations.