Flow Injection-Chemiluminescence Method for Determination of Hydrocortisone in Human Serum by Using Trivalent Silver Complex

A flow-injection chemiluminescence (FI-CL) reaction system with diperiodatoargentate (III) (DPA) was developed for determination of hydrocortisone in human serum. The weak chemiluminescence signal from the reaction between DPA and sulfuric acid system could be greatly enhanced in the presence of hydrocortisone. The optimal conditions of the CL system were: 1.0 M H2SO4, 2.5 x 10(-4) M DPA, and flow rate of 4.20 mL min(-1). Under the optimal conditions, the CL intensity was linear to the concentration of hydrocortisone from 3.0 x 10(-10) g mL(-1) to 1.0 x 10(-7) g mL(-1) with a detection limit of 2.2 x 10(-10) g mL(-1) (3 sigma). The relative standard deviation (RSD) was 0.63% (n = 11) for 5.0 x 10(-8) g mL(-1) hydrocortisone solution. The proposed method was successfully applied to the determination of hydrocortisone in serum samples with the recoveries of 93.0%.-110.0%, and the RSDs were 0.7%-2.5%. The possible chemiluminescence mechanism was discussed by use of fluorescence spectra and UV-vis absorption spectra.