Influence of the solvent on the gas chromatographic behaviour of urea herbicides

Abstract

SummaryDegradation products of chlorsulfuron, chlortoluron, diuron, fluometuron, isoproturon, Iinuron, metabenzthiazuron, metobromuron, and monuron formed in the gas chromatographic injector have been used for identification of the respective herbicides. Mass spectra of the derived compounds were obtained with a quadrupole mass spectrometric detector working in scan mode (20-450 amu). The compounds generated often depended on the solvent used for phenylurea herbicide injection (ethanol, methanol, dichloromethane, and acetonitrile). When methanol and ethanol were used as solvents the major products formed from phenylureas were carbamic acid esters. When acetonitrile or dichloromethane were used the main derivatives were phenylisocyanates. Chlorsulfuron and metabenzthiazuron, however, generated a triazine plus a phenylsulfonamide and a benzothiazolamine, respectively, irrespective of the solvent used. Linuron and diuron behaved similarly and gave degradation products with the same mass spectra. The thermal reactions occurred instantaneously in the injector block and were promoted by the high temperature selected (300 ~ Determination of the compounds derived from urea herbicides, by use of a 30 m BP10 column and a selected ion registering (SIR) program based on l",,vo or three ions, can be used for sensitive detection of the presence of urea herbicides in environmental extracts. With standards in methanol instrument detection limits ranged from 02 pg for chlorsulfuron (detected as 2-chlorobenzensulfonamide) to 1 pg for monuron and metobromuron (both detected as their carbamic acid methyl esters). RSDwere below 9% at the 5 ng L 1 level. The response was linearly dependent on quanti b, (r> 0.9986) in the 5 ng L 1 to 25 I~g L 1 range. Unequivocal identification of some phenylurea herbicides was not always possible because some herbicides with similar structures, for example diuron and hnuron, gave the same derivative.

Application of solid-phase microextraction for determining phenylurea herbicides and their homologous anilines from vegetables

“…Under controlled conditions phenylureas can be determined from waters by SPME-GC in form of their respective derived anilines [32]. The gas chromatographic behaviour of the urea herbicides has been recently studied [33][34][35], the use of high temperatures at the injector port facilitates the degradation of the herbicide in a derived product, which depends on the solvent used for injection [36].…”

Gas chromatographic behaviour of urea herbicides

“…The analogous carbamic acid methyl esters were found instead of the phenylurea herbicides. 2-aminobenzothiazol was found from metabenzthiazuron and 2-amino-4-methoxy-6-methyl-l,3,5-triazine from chlorsulfuron [36].…”

“…Other authors [21,27,29,30] reported phenylurea determination in form of their analogous phenylisocyanates but they used different non-alcoholic solvents for injection. The importance of the solvent in the GC analysis of urea herbicides has been recently studied [36]. Figure 1 shows the chromatograms obtained from the three GC instruments using different injection modes.…”

FI-photoinduced Chemiluminescence Method for Diuron Determination in Water Samples

“…26 Capillary electrophoresis [27][28][29] and multivariate calibration methods 30 have been also employed.…”