A rapid assay capable of detecting several commonly used herbicides at
nanogram per milliliter concentrations in biological fluids is descri
bed. The assay is based on inhibition of photosynthetic electron trans
port in spinach thylakoids by the target compounds with colorimetric d
etection using a redox dye. Using a microtiter plate format, high thro
ughput assays of water, urine, and homogenized tissue were performed i
n minutes with minimal sample preparation. Detection limits of 3 ng/mL
for atrazine, 3 ng/mL for diuron, and 1 ng/mL for terbutryn were obse
rved.