Highly sensitive and specific assay of plasma melatonin using high-performance liquid chromatography with fluorescence detection preceded by solid-phase extraction.

This paper describes a new, highly sensitive, rapid method for the determination of low levels of endogenous melatonin, the pineal and retinal hormone, in fish plasma samples. The combination of solid-phase extraction and high-performance liquid chromatography with fluorescence detection significantly improves the separation and increases the sensitivity of the assay. The proposed method may be a useful alternative to previously reported procedures. The assay should be applicable to plasma and tissue samples from other animals, including humans, with only minor modifications.