A RADIOACTIVE-TRACER TECHNIQUE FOR THE STUDY OF LETHAL BODY BURDENS OF NARCOTIC ORGANIC-CHEMICALS IN DAPHNIA-MAGNA

High analytical costs and high detection limits have constrained experimental analyses in aquatic ecotoxicology. To circumvent these restrictions, we have assessed a novel radiotracer approach to tissue residue analysis, using 10, C-14-labeled narcotic organic chemicals. Daphnia magna was exposed to potentially lethal concentrations of acetone, acetophenone, benzene, benzoic acid, butanol, 1,2-dichlorobenzene, 2-methylnaphthalene, 1,1,2,2-tetrachloroethane, 1,2,4-trichlorobenzene, and toluene. Analysis of the body burdens after 48-h exposure showed that the radiotracer method could measure chemical levels in single Daphnia at body concentrations ranging from 0.02 to 6310 mmol/kg, depending on the chemical. The lowest body residue of 0.02 mmol/kg was well above the lower limits of detection of almost-equal-to 1 nmol/kg. The technique measured body residues of lipophobic (K(ow) = 0.55, acetone) and lipophilic (K(ow) = 16 000,1,2,4-trichlorobenzene) chemicals equally well. The radioactive tracer technique is simple, sensitive, widely applicable, and economical.