BOUND AND EXTRACTABLE C-14 RESIDUES IN CANOLA (BRASSICA-NAPUS) PLANTS TREATED WITH RADIOLABELED ATRAZINE

The nature and distribution of C-14 atrazine (2-chloro- 4 -ethylamino- 6 -isopropylamino-s-triazine) residues in resistant and susceptible canola (Brassica napus L.) varieties were studied. Radiolabelled atrazine was applied to the plants just before the flowering stage and continued for 10 days. The plants were harvested 3, 10 and 25 days after the end of the treatment. The roots, shoots and pods of each plant were exhaustively extracted with methanol. The C-14 distribution between the methanol extracts and the plant matrix fractions (bound residues) was similar for the two varieties. High-pressure liquid chromatographic analysis of the methanol extracts showed that they contained two unknown metabolites (possibly conjugates) in addition to atrazine. The bound C-14 residues were released by supercritical methanol extraction and analysed by thin-layer chromatography, gas chromatography and high-pressure liquid chromatography. Several C-14 components in the released material were detected. Bound atrazine and its two dealkylated metabolites represented only a very small portion (10-18%) of the total bound C-14 residues in the plants.