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 (LT50) was recorded and cross -referenced to the appropriate calibration curve. Using known standards, co mparable results were obtained using the bioassay and GC-MS. The bioassay a llows concentrations of synthetic pyrethroids as low as I pg L-1 to be meas ured 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 tens ions 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 prel iminary assessment of water contamination.