Development and validation of a high-performance liquid chromatographic method for the determination of clomazone residues in surface water

Development of selective preconcentration/clean-up method for imidazolinone herbicides determination in natural water and rice samples by HPLC-PAD using an imazethapyr imprinted poly(vinylimidazole-TRIM)

The development of a novel molecularly imprinted solid-phase extraction (MISPE) method for simultaneous preconcentration of imazapyr (IMP), imazapic (IMZ) and imazethapyr (IMT) with determination by HPLC-PAD (High performance liquid chromatography - photodiode-array detector) is proposed. The polymer synthesis was performed using imazethapyr as template molecule and 1-vinylimidazole as functional monomer. The method is based on preconcentration of 100.0 mL of sample through 200.0 mg of molecularly imprinted poly(vinylimidazole-TRIM) (MIP-1VN) at pH 4.0, followed by elution with 2.0 mL of MeOH:CH₂Cl₂:HAc (34:62:4, v/v). The range of analytical curve (0.29-200.0, 0.21-200.0 and 0.15-200.0 µg L^-1), limits of detection (0.09, 0.06 and 0.04 µg L^-1) and preconcentration factors (92, 96 and 98) determined for the herbicides, IMP, IMZ and IMT, respectively, were greatly superior when compared with those ones obtained with commercial adsorbents. The analytical method was successfully applied to spiked surface water and rice samples with good results of recovery values (86-107%).

Contamination of rice field water with sulfonylurea and phenoxy herbicides in the Muda Irrigation Scheme, Kedah, Malaysia

The purpose of the present study was to investigate the potential risk of herbicide contamination (2,4-dichlorophenoxy (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), metsulfuron, bensulfuron, and pyrazosulfuron) in the rice fields of the Muda Irrigation Scheme, Kedah, Malaysia. The study included two areas with different irrigation water sources namely non-recycled (N-RCL) and recycled (RCL) water. Periodic water sampling was carried out from the drainage canals during the planting period of the wet season 2006/2007 and dry season 2007. The HPLC-UV was used to detect herbicide residues in the water samples collected from the rice fields. The results showed that the concentration of sulfonylurea herbicides such as bensulfuron and metsulfuron in the rice field was 0.55 and 0.51 μg/L, respectively. The potential risk of contamination depended on the actual dosage of each herbicide applied by farmers to their rice fields. The potential risk of water pollution by the five herbicides studied in the area with RCL water tended to be more widespread compared to the area with N-RCL water due to surface water runoff with higher levels of weedicides to the surrounding areas. During the two seasons, 50-73% of the water samples collected from the area receiving RCL water contained the five herbicides studied at concentrations of more than 0.05 μg/L, and this percentage was higher than that from the areas receiving N-RCL water (45-69%). During the wet season, the overall total mean concentration of the eight herbicides found in the samples collected from the area with RCL water (6.27 μg/L) was significantly higher (P < 0.01) than that from the area receiving N-RCL water (2.39 μg/L). Meanwhile, during the dry season, there was no significant difference (P > 0.05) in the herbicide concentrations between the areas receiving RCL (6.16 μg/L) and N-RCL water (7.43 μg/L) water.

Integrated assessment of biomarker response in carp (Cyprinus carpio) and silver catfish (Rhamdia quelen) exposed to clomazone

Clomazone is considered a potential contaminant of groundwater and is persistent in the environment. To verify the effects of clomazone in Cyprinus carpio and Rhamdia quelen, a method that combines biomarker responses into an index of "integrated biomarker response" (IBR) was used for observed biological alterations in these species. Thiobarbituric acid-reactive substances in liver of carp and silver catfish decreased at both concentrations tested. However, in muscle it increased in carp at 3 mg/L and silver catfish at 6 mg/L. Protein carbonyl increased in liver (3 and 6 mg/L) and muscle (6 mg/L) of carp. In carp, superoxide dismutase (SOD) increased at 3 mg/L and catalase at 6 mg/L. In silver catfish, SOD in liver decreased at 3 mg/L. Glutathione-S-transferase increased at 3 mg/L in muscle of carp. Nonprotein thiol levels decreased at both concentrations in liver of silver catfish and muscle of carp. In silver catfish, acetylcholinesterase (AChE) decreased in brain at 6 mg/L. Nevertheless, AChE in muscle of both species increased at 3 and 6 mg/L. IBR was standardized scores of biomarker responses and was visualized using star plots. The IBR values shown that in carp there was predominantly an induction of parameters, whereas in silver catfish there was inhibition of these responses. In this way, IBR may be a practical tool for the identification of biological alterations in fish exposed to pesticides. In the present study, IBR was efficient for comparisons of fish species using clomazone. This study may serve as a base for evaluation of other pesticides in the rice field, environment, or laboratory experiment.

A colorimetric method for determination of γ-glutamyl-S-ethenyl-cysteine in narbon vetch (Vicia narbonensis L.) seeds

A new colorimetric method based on the bleaching of the iodoplatinate ion has been developed for fast and easy determination of γ-glutamyl-S-ethenyl-cysteine (GEC) in narbon vetch (Vicia narbonensis L.) seeds. The calibration curve showed a good correlation (r(2)=0.9959) between absorbance and GEC amounts from 5.5 to 33 μg (10-59.78 μmol/L). The limits of detection and quantification were 1.16 and 3.55 μmol/L, respectively, and no significant interferences from other sulfur-containing compounds were observed. The method showed excellent repeatability (relative standard deviation [RSD]=0.28%), reproducibility (RSD=4.4%), and accuracy (94%). Determination of GEC in 20 narbon vetch accessions yielded values that were in agreement with those reported previously using capillary electrophoresis and high-performance liquid chromatography methods. The method could be especially valuable for determination of GEC during the process of production of new low-GEC narbon vetch varieties.

A clomazone immunoassay to study the environmental fate of the herbicide in rice (Oryza sativa) agriculture

The environmental impact of rice agriculture is poorly studied in developing countries, mainly due to limitations of the analytical capacity. Here, we report the development of a clomazone enzyme-linked immunosorbent assay as a fast and cost-effective tool to monitor the dissipation of this herbicide along the harvest. Antibodies were prepared using different strategies of hapten conjugation, and the best hapten/antibody pair was selected. It proved to be a reliable tool to measure the herbicide in the 2.0-20 ng/mL range in field samples, with excellent correlation with high-performance liquid chromatography results. The assay was used to study the dissipation of the herbicide in the floodwater of experimental rice paddies in Uruguay. Large differences in the residual amounts of herbicide were observed depending on the flooding practices. Because of its robustness and simplicity, the assay may be useful to delineate and monitor management practices that can contribute to minimizing the release of the herbicide in the environment.

Gas chromatographic method for the determination of hexaconazole residues in black tea

A highly reliable, quantitative and sensitive analytical method for determining the residues of the fungicide, hexaconazole in black tea is described. The proposed method is based on liquid-liquid extraction followed by gas chromatographic determination, using nitrogen phosphorus detector (GC-NPD) for the identification and quantitation of hexaconazole. The most appropriate solvent mixture for extracting hexaconazole residues from black tea was n-hexane:acetone at 1:1 (v/v). The extract was cleaned up by adsorption column chromatography using activated florisil. Performance of the method was assessed by evaluating quality parameters such as recovery value, repeatability, reproducibility, linearity and limits of detection and quantitation. When the method was assessed for repeatability, the percentage of recovery ranged between 86% and 96% while the relative standard deviation was between 0.30% and 2.35%. In studies on reproducibility the recovery ranged from 81% to 85% and relative standard deviation from 1.68% to 5.13%, implying that the method was reliable. A field trial was conducted to verify the application of this method with real samples. Results prove that the validated method was suitable for extracting hexaconazole residues.