Gas chromatographic determination of ametryn and its metabolites in tropical root crops
Bardalaye, P.C.; Wheeler, W.B.
Journal - Association of Official Analytical Chemists 67(2): 280-284
1984
ISSN/ISBN: 0004-5756 PMID: 6725197 Document Number: 224856
Residue analysis of the herbicide ametryn is widely known but an analytical method for determining its metabolites has not yet been reported in the literature. A method was developed for the extraction and determination of ametryn and 3 metabolites, 2-methylthio-4-amino-6-isopropylamino-s-triazine (GS-11354), 2-methylthio-4,6-diamino-s-triazine (GS-26831) and 2-methylthio-4-amino-6-ethylamino-s-triazine (GS-11355) in taniers, yams and cassava. Residues were extracted from crops with ethyl acetate-toluene (3 + 1 vol/vol), using a Polytron homogenizer and anhydrous sodium sulfate added for drying. The extracts were cleaned up by automated gel permeation chromatography on Bio-Beads SX-3 gel in the same solvent system. Quantitative determination was performed by gas chromatographic (GC) analysis on a column packed with 5% DEGS-PS on 10-120 mesh Supelcoport using an N-P detector or a flame photometric detector (FPD) in the S mode. Minimum detection by the flame photometric detector was 10 ng each for ametryn, GS-11354 and GS-11355 and 21 ng for GS-26831; by the N-P detector, 0.3 ng of each component gave easily quantitatable peaks. On a parts/million basis, starting with 25 g sample, the FPD detected a minimum level of 0.04 .mu.g/g each for ametryn, GS-11354 and GS-11355, and 0.08 .mu.g/g for GS-26831. The N-P detector detected 0.0024 .mu.g/g for all 4 compounds. In addition to superior sensitivity, instrumental conditions allowed the complete separation of components in 10 min, for the N-P detector; > 30 min was required for the FPD. Recoveries from fortified crops ranged from 67-111% at levels of 0.1-1.0 .mu.g/g.