USE OF A MINIATURIZED TEST SYSTEM FOR DETERMINING ACUTE TOXICITY OF TOXICITY IDENTIFICATION EVALUATION FRACTIONS

A miniaturized test system was developed and used to determine the acu te toxicity of effluent fractions separated by HPLC to Daphnia magna a nd Pimephales promelas. The miniaturized test system consists of expos ing test organisms in 1 mi of test solution using 48-well microtiter p lates for the test vessels. Several factors were investigated to deter mine the acceptability of this test system. These factors included org anism biomass to test solution ratio, toxicity of the microtiter plate s to the organisms, dissolved oxygen in the test solution, partitionin g of the test chemicals to the walls of the test vessels, and dilution of the test solution when the organisms are transferred. Toxicity of four reference chemicals to D. magna and P. promelas was also determin ed using the miniaturized test systems. It was concluded that the test system could be miniaturized and still provide results comparable to those obtained when standard U.S. EPA test procedures were used. The m ajor benefit of using the miniaturized test system is that less soluti on is required for conducting a toxicity test. This becomes important when only a small amount of test solution is available, as might occur during a toxicity identification evaluation, after an effluent has be en fractionated by HPLC. Other benefits include less space required to conduct a test, less time necessary to prepare test solutions, and a reduced volume of Waste for disposal. (C) 1996 Academic Press, Inc.