In-Column and Post-Column Photochemical Fluorescence Enhancement in Packed Capillary Liquid Chromatography

A photochemical reaction detection system coupled with a 320-μm I.D. packed fused-silica HPLC analytical column is described. This reaction detection system does not require the addition of reagent, hence it is suitable for combination with a miniaturized analytical column. As a model system, the separation and detection of some dansylated chlorophenols was chosen. In the photochemical reactor, the main reaction product is 5-dimethylaminonaphthalene-1-sulphonic acid (dansyl-OH), which is determined by fluorescence monitoring. Both the photochemical reaction after the column and in the end part of the column (‘in-column’) were investigated and a comparison between the two approaches was made. In both cases, band broadening due to the photochemical reaction detection system was less than 0.1 μl. In-column detection of the photochemical reaction product was investigated in order to study the possibility of carrying out separation, derivatization and detection in the analytical column. An increase in signal-to-noise ratio of more than an order of magnitude was obtained when compared with detection after the column.