Biological Detection Technique of Butachlor

A biological method, based on butachlor inhibitory effect on plant growth, was examined for its application to detect this herbicide. Analysis of seed germination inhibition showed that, among the 3 vegetables tested, edible amaranth was the most sensitive to 10.3 mM butachlor within 3 days after treatment (DAT), with 100% inhibition in 2 days. Analysis of hypocotyl growth inhibition showed that 5 vegetables, including Chinese mustard, Ching-Geeng, edible amaranth, field mustard and radish, expressed a similar and constant sensitivity to 10.3 mM butachlor, with 70 to 80% inhibition 2 to 3 DAT. In addition, radicle growth inhibition analysis showed that, among these 5 vegetables, Chinese mustard was the most sensitive to 10.3 mM butachlor, with 90% inhibition 3 DAT; and field mustard and edible amaranth were more sensitive to this herbicide than the remaining 2 vegetables. Further dose-response analysis indicated that linear regressions existed between seed germination of edible amaranth or hypocotyl and radical growth of edible amaranth and Chinese mustard in one to three days and the log-transformed concentrations of butachlor. For the instrumental detection of butachlor, which organic solvent extraction and HPLC analysis, a linear regression between integrated peak area of HPLC system and butachlor concentration in extraction solution was observed ranged from 0.02 to 0.10 mM, with a ten-fold higher detection sensitivity than bioassay system. A comparison of biological with instrumental methods using a soil spiked with a given concentration of butachlor as the test sample showed that bioassay system consisting of early growth responses of both edible amaranth and Chinese mustard, especially the seed germination response of edible amaranth within 2 to 3 DAT, could be recommended to predict butachlor concentration, to replace the expensive HPLC system. The latter is harmful to environment due to the toxic organic solvents used for instrumental analysis.