Fluorimetric determination of danthron in pharmaceutical tablets and in urine

A simple, rapid determination is reported for danthron (1,8-dihydroxyanthraquinone) in pharmaceutical tablets. In a flow-injection system, danthron is reduced by sodium dithionite in $\text{1}\text{1}$ methanol/borate buffer to give a fluorescent complex. Linearity ranges from 30 μg ml^?1 to below 0.1 μg ml^?1. In urine samples, danthron is separated from other fluorescing species by reversed-phase high-performance liquid chromatography before its reduction by dithionite in a post-column reactor. Urine preparation requires no extraction. Spiked urine samples were studied in the working range of 0.02–2.0 μg ml^?1 danthron.