Simple Biological Detection Technique Instead of Instrumental Analysis of Butachlor

A biological method, based on butachlor inhibitory effect on plant growth, was examined for its application to detect this herbicide without using professional instruments. Analysis of seed germination inhibition showed that edible amaranth was sensitive to 10.3 mM butachlor, with 100% inhibition 2 days after treatment (DAT). Analysis of hypocotyl growth inhibition showed that 2 vegetables including Chinese mustard and edible amaranth, had a similar and constant sensitivity to 10.3 mM butachlor, with 80 to 82% inhibition 2 DAT. In addition, radicle growth inhibition analysis showed that, Chinese mustard and edible amaranth were all sensitive to 10.3 mM butachlor, with 86 and 89% inhibition 2 DAT, respectively. 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, and the log-transformed concentrations of butachlor. For the instrumental detection of butachlor, with 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 ten-fold higher detection sensitivity than bioassay system. A comparison of biological with instrumental methods using a 20-g soil spiked with 102.9 μmole butachlor as the test sample showed that bioassay system, especially the seed germination response of edible amaranth having 63% of predicted concentration compared with that determined by instrument, could be recommended to predict butachlor concentration by farmers or growers, to replace the expensive and complicated HPLC system. The latter is also harmful to environment due to the highly toxic organic solvents used as mobile phase for HPLC system.