A bioassay for the measurement of insecticide concentration

A bioassay was developed to measure insecticide residues using fruit flies (Drosophila melongaster). After adding a known volume of sampling solution, the time at which 50% of the flies were dead (LT(50)) was recorded and cross-referenced to the appropriate calibration curve. Using known standards, comparable results were obtained using the bioassay and GC-MS. The bioassay allows concentrations of synthetic pyrethroids as low as 1 pg L(-1) to be measured with a variance of < 5%. The bioassay can be used reliably over a wide range of temperatures and it is tolerant to a range of pH and surface tensions of the test solution. The whole bioassay is compact, physically robust, and simple to use; hence, it could be of use in the field as a quick preliminary assessment of water contamination.