Improved HPLC determination of acidic opines by phenylisothiocyanate derivatization and its application to marine animals.

We present here a reliable and sensitive method for the determination of acidic opines such as meso-alanopine, beta-alanopine, tauropine and strombine in biological samples. Interfering primary amino acids were eliminated by reaction with o-phthalaldehyde, and the derivatized compounds were passed through Sep-Pak Plus PS-1 cartridges. The acidic opines were recovered by flushing the cartridges with water, then determined by high performance liquid chromatography after a second derivatization with phenylisothiocyanate. All 4 acidic opines were detected within 30 min. This method ensured good separation and guaranteed almost full recovery of all acidic opines. This method was applied to analyze opines in marine animals and to test whether opines are metabolized in the livers of the rat and fish.