Bentazon

Cytochrome P-450 is frequently the oxygenase which detoxifies xenobiotics, including herbicides. Blocking the metaboHsm of a herbicide increases the activity or delays the inactivation, thus increasing the effectiveness of such herbicides as chlortoluron [15545-48-9] and bentazon [25057-89-0]... 

Bentazone has been monitored in the NRA Anglian Region since 1993 and the results show that bentazone is regularly present in surface and groundwaters. Currently there are no restrictions on its use, but bentazone is due to be reviewed under the Authorizations Directive, the new European legislation for pesticide approvals, and the issue of water pollution will be raised. 

Once pesticides were identified, monitoring was undertaken by the NRA, where possible, to confirm the usefulness of the model predictions. The most important prediction from the model was that the herbicide bentazone would reach surface waters. Subsequent analysis by the NRA confirmed the detection of bentazone at concentrations above 0.1 /tg D Consequently, the NRA informed... 

Another example is the determination of bentazone in aqueous samples. Bentazone is a common medium-polar pesticide, and is an acidic compound which co-elutes with humic and/or fulvic acids. In this application, two additional boundary conditions are important. Eirst, the pH of the M-1 mobile phase should be as low as possible for processing large sample volumes, with a pH of 2.3 being about the best that one can achieve when working with alkyl-modified silicas. Secondly, modifier gradients should be avoided in order to prevent interferences caused by the continuous release of humic and/or fulvic acids from the column during the gradient (46). 

With bentazone, small changes in the composition of the mobile phase have a dramatic effect on the final results (see Eigure 13.7). 

Figure 13.7 Selectivity effected by employing different step gradients in the coupled-column RPLC analysis of a surface water containing 0.40 p-g 1 bentazone, by using direct sample injection (2.00 ml). Clean-up volumes, (a), (c) and (d) 4.65 ml of M-1, and (b) 3.75 ml of M-1 transfer volumes, (a), (c) and (d), 0.50 ml of M-1, and (b), 0.40 ml of M-1. The displayed cliromatograms start after clean-up on the first column. Reprinted from Journal of Chromatography, A 644, E. A. Hogendoom et al, Coupled-column reversed-phase liquid chromatography-UV analyser for the determination of polar pesticides in water , pp. 307-314, copyright 1993, with permission from Elsevier Science.

Figure 13.15 Chromatograms obtained by on-line ti ace enrichment of 50 ml of Ebro river water with and without the addition of different volumes of 10% Na2S03 solution for every 100 ml of sample (a) blank with the addition of 1000 p.1 of sulfite (b) spiked with 4 p.g 1 of the analytes and 1000 p.1 of sulfite (c) spiked with 4 p.g 1 of the analytes and 500 p.1 of sulfite (d) spiked with 4 p.g 1 of the analytes without sulfite. Peak identification is as follows 1, oxamyl 2, methomyl 3, phenol 4, 4-niti ophenol 5, 2,4-dinitrophenol 6, 2-chlorophenol 7, bentazone 8, simazine 9, MCPA 10, atrazine. Reprinted from Journal of Chromatography, A 803, N. Masque et ai, New chemically modified polymeric resin for solid-phase extraction of pesticides and phenolic compounds from water , pp. 147-155, copyright 1998, with permission from Elsevier Science.

Kim J-E, E Fernandes, J-M Bollag (1997) Enzymatic coupling of the herbicide bentazon with humus monomers and characterization of reaction products. Environ Sci Technol 31 2392-2398. 

There are a large number of literature references that refer the use of SPE cartridges for the extraction of pesticides from water. There are several comprehensive reviews of the use of SPE, including that by Soriano et al. who discussed the advantages and limitations of a number of sorbents for the analysis of carbamates. Hennion reviewed the properties and uses of carbon based materials for extraction of a wide multiclass range of pesticides. Thorstensen et al. described the use of a high-capacity cross-linked polystyrene-based polymer for the SPE of phenoxy acids and bentazone, and Tanabe et al reported the use of a styrene-divinylbenzene copolymer for the determination of 90 pesticides and related compounds in river water. SPE cartridges are also widely used for the cleanup of solvent extracts, as described below. 

Soybeans CZE UV 11-85 ugkg- 50 mM acetate Acifluorfen, 2,4-D, bentazone, thifensulfuron-methyl, chlorimuron-ethyl, imazaquin 129... 

Chiron et al. used HPLC/ESI-MS in the negative mode for the determination of acidic herbicides in environmental waters. The acidic herbicides investigated were benazolin, bentazone, 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-... 

Restricted access phases are another approach to exploiting the differences in characteristics of analytes. Large analytes are excluded from an internal surface on which an adsorptive stationary phase is present. A herbicide analysis for Metsulfuron methyl, Bentazone, Bromoxynil, methylchlorophenoxy acid, and Mecoprop in the presence of humic acid was performed on restricted access reversed phase media.52 The cytostatic compound epirubicin and its metabolites were separated from plasma using a Pinkerton GFF II column.53 Gradient separations of polymers on reversed phase and on normal phase represent an alternative to gel permeation chromatography. Polyesters of noncrystalline materials were separated on a variety of such phases.54... 

Analysis of pesticides (eight in total, namely, molinate, propanil, fenitrothion, malathion, bentazone, cypermetrine, maloxon, and fenitrothion oxon) in biota was accomplished with a method based on pressurized liquid extraction (ASE), followed by SPE clean-up, and analysis by gas chromatography-mass spectrometry with electron impact ionization (GC/MS-EI). 

Bentazone and MCPA were the most ubiquitous compounds (detected in 100% of the samples), whereas malathion followed by MCPA and molinate were the compounds found at highest concentrations (5,825, 4,197 and 3,590 ng/L, respectively). Pesticide profiles similar to this have been observed previously in the studied area, as... 

Comparison of the pesticide concentrations (ng/L) found in this study in sites HDCD and HD AD with those measured in a previous study performed in 2005 in the same sampling sites [ 16, 20] showed a general good agreement for all pesticides except for bentazone, MCPA, propanil, and atrazine, which presented now comparatively lower concentrations, and alachlor, malathion, diuron, and molinate, whose concentrations have increased considerably (Fig. 3). 

In several AT studies, pesticide levels in the Ebro were found to be high. Hildebrandt et al. [50] found a homogeneous contamination pattern from atrazine (and also from simazine from May 2000) in intensive Rioja cultivation areas throughout the Ebro. Nearer to the delta, Barata et al. [72] found high levels of bentazone, methyl-4-chlorophenoxyacetic acid, propanil, molinate and fenitrothion in water, while Kuster et al. [71] found low concentration levels of atrazine and simazine at the delta, but high levels of other pesticides used in rice cultivation. Importantly, Hildebrandt et al. [50] found that levels of pesticides in groundwater... 

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