Identification of products formed during UV irradiation of tamoxifen and their use for fluorescence detection in high-performance liquid chromatography.

During the UV irradiation of tamoxifen, isomerization of the trans to the cis isomer takes place and consequently corresponding highly fluorescent phenanthrene derivatives are formed. Their formation can be used for the sensitive and selective detection of tamoxifen in high-performance liquid chromatography (HPLC). The structure of photoproducts was identified by 1H NMR spectroscopy, HPLC, gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. Owing to the variety of products formed and the higher selectivity and fluorescence response, on-line postcolumn photocyclization is preferred to the precolumn mode. A chromatographic system for the separation of isomers and photoproducts is suggested.