Flow injection chemiluminescence detection and solvent extraction for human skin ointment dexamethasone acetate absorption analysis and the reaction mechanism study

A flow-injection chemiluminescence (CL) method coupled with solvent extraction for the determination of dexamethasone acetate (DA) in ointment was presented in this paper. It was based on the enhancing effect of the studied drug on CL emission of luminol–K3Fe(CN)6 system. This method has the advantages of simple sample treatment, cheap instrumentation and rapid detection. Under the optimum conditions, relative CL intensities were proportional to DA concentrations in the 0.044–4.4 μg ml−1 range. The limit of detection was 0.01 μg ml−1 (3σ) for DA. The method was applied to DA quantification in commercial DA ointment pharmaceutical and to human skin DA absorption analysis. Experiments were performed to evaluate the nature of DA enhanced luminol–K3Fe(CN)6 CL reaction. Based on the experimental results, it was suggested that in this CL system, DA was oxidized by K3Fe(CN)6 to form a medium product (DAox), DAox oxidized luminol with a faster kinetic step comparing with K3Fe(CN)6 oxidized luminol to an active form. As a result, DA speed the luminol CL reaction, and finally intensified the CL signal.