An easy-to-use excimer fluorescence derivatization reagent, 2-chloro-4-methoxy-6-(4-(pyren-4-yl)butoxy)-1,3,5-triazine,for use in the highly sensitive and selective liquid chromatography analysis of histamine in Japanese soy sauces

In this study, a novel pre-column excimer fluorescence derivatization reagent, 2-chloro-4-methoxy-6-(4-(pyren-4-yl)butoxy)-1,3,5-triazine (CMPT), was developed for polyamines, specifically histamine. By CMPT derivatization, the polyamines, histamine and tyramine were converted to polypyrene derivatives, and emitted intra-molecular excimer fluorescence at 475 nm. This could clearly be distinguished from the normal fluorescence emitted from reagent blanks at 375 nm. Unlike conventional excimer fluorescence derivatization reagents, CMPT is chemically stable and its reactivity sustained over at least 36 days even in solution state. We successfully applied this reagent to the sensitive and selective analysis of histamine in different kinds of Japanese commercial soy sauces. The detection and quantification limits of histamine were 15 and 50 μg L⁻¹, respectively, equating to 1.35 pmol and 4.5 pmol for a 6 μL injection. This sensitivity helped the direct analysis of soy sauce samples only treated by one-step liquid–liquid extraction without concentration. The histamine levels of commercial soy sauce samples (koikuchi, usukuchi and saishikomi) investigated were 1.24–768.5 mg L⁻¹.