2.5 Paraquat concentration measurement with a spectrophotometer
For each microcosm, 10 milliter of water was pipetted into a test tube. After that, two milliliters of 0.2% sodium dithionite were added, and the solution was mixed by shaking the tube twice. A portion was placed in a 1.0 cm. cell and absorbance at 396 nm was recorded [5].