Groundwater dating using radiocarbon in fulvic acid in groundwater containing fluorescein

•Separation method of fulvic acid and fluorescein was proposed.•Humic and fulvic acids were isolated from contaminated groundwater with fluorescein.•DO14C for fulvic acid was estimated from the mixture of fulvic acid and fluorescein.•DO14C age for fulvic acid was compared with groundwater age estimated by He.