DIOXETANE CHEMILUMINESCENCE DETECTION IN LIQUID-CHROMATOGRAPHY

A study of the potential of dioxetane chemiluminescence (CL) detection in reversed-phase column liquid chromatography is presented. 3,4-Diethoxy-1,2-dioxetane (DEDO) is generated on-line in a post-column photochemical reactor from 1,2-diethoxyethylene (DEE) and singlet oxygen; the latter is produced photochemically by the eluting compounds via oxygen quenching. CL is obtained by thermal decomposition of DEDO in the detector cell (kept at 70.0-degrees-C) in the presence of 9,10-dibromoanthracene (DBA). In the experimental set-up two post-column reagent addition lines are applied, providing DEE in acetonitrile before and DBA in tetrahydrofuran after the photochemical reactor. The photochemical reactor is a knitted PTFE tube, irradiated with a medium-pressure mercury lamp in combination with a filter cuvette in order to prevent autoxidation of DEE. The experimental conditions were optimized. Reversed-phase chromatograms applying exclusively acetonitrile-water (90 + 10, v/v) are presented and CL detection is compared with UV absorption detection. For a number of analytes the concentration detection limits in both techniques are similar, i.e., in the 10(-8)-10(-7) M range. Other compounds, although providing strong absorption signals, hardly provide any CL, thus indicating the selectivity of the new technique.