Immunoassays for two groups of organochlorine insecticides, cyclodienes (endosulfan and heptachlor) and DDT were applied to the analysis of a diverse range of plant-derived foods. Water-miscible solvent extracts of high-moisture, low-fat foods such as cauliflower, cabbage, green and red blue grapes and tomato caused little or no interference with the assays, enabling methanol or acetonitrile extracts of the foods to be analysed directly by immunoassay, after dilution in assay buffer. Reasonable recoveries of spikes of these pesticides were obtained by direct analysis of extracts of spiked commodities, with reliable detection down to 0.025 mg kg (1 heptachlor or endosulfan and 0.1 mg kg (1 DDT in the commodities. Acetonitrile extracts of milk could also be analysed directly for DDT. In contrast, extracts of low moisture, non-fatty (rice) and fatty (cottonseed) food commodities interfered appreciably with the assays, reducing assay colour and detection sensitivity. Some simple cleanup methods were developed to remove interference and enable detection of spiked organochlorines in these foods. Extracts of coloured foods, such as tea, coffee and spinach caused similarly major interference in the assays, and a number of simple clean-up methods were ineffective in removing interference. However, use of an immunoaffinity chromatography method for cyclodienes enabled quantitative recoveries to be obtained in extracts of several of these foods when analysed by either ELISA or gas chromatography. Direct analysis was suited for screening purposes but immunoaffinity chromatography results were more quantitative. These results indicate that ELISAs can be
A method based on the hydrolytic debromination of ethylene dibromide (EDB) in the presence of an oxidizing agent has been developed. Bromine liberated from inorganic bromide is used to brominate p-rosaniline. The intensity of the resulting violet-red bromo compound in chloroform is measured at 580 nm. The relationship between absorbance and concentration of EDB is linear in the range of 5–60 μg. The method is very sensitive and as little as 0.50 ppm unchanged EDB residue in a 20 g sample of fumigated grain and 1 ppm EDB in a 10 ml air sample can be detected.
Sorption is one among the many techniques available for the removal of organic materials from potable water and waste water. Use of locally available Wood Charcoal (WC) is essential in place of costly activated charcoal to make the process more economical and lucrative. The vital objective of this investigation was to assess the performance of WC for the removal of DDT from the aqueous phase. The influence of important factors like, particle size, pH, and time of contact, which affects the sorption process was studied in this investigation using batch experiments. The removal kinetics were carried out under the temperature 27 degrees +/- 1 degrees C (room temperature) and the sorption kinetics constants were evaluated. Sorption equilibria study has also been carried out to develop the Freudlich's sorption isotherm equation from which the ultimate sorption capacity of WC for sorption of DDT was calculated.
A thin-layer chromatographic method using a novel chromogenic reagent was developed to detect the phosphorothionate and phosphorothiolothionate groups of pesticides. On reaction with 4-am'mo-N,N-diethylaniline and subsequent exposure to bromine vapor, these compounds yield a deep magenta product. The chromogenic reagent is specific to these organophosphates and gives no response to phosphorothiolates and substituted phosphonates. The method is rapid and highly sensitive. The limit of detection is 0.05-0.5 μg.
Methomyl (S-methyl-N-[(methylcarbamoyl) oxy] thioacetimidate) is converted to oxime and hydroxylamine by alkali and acid treatment, respectively. Hydroxylamine is oxidized with iodine in the presence of sulfanilic acid to yield p-diazoniumbenzenesulfonic acid which is coupled with α-naphthylamine to form a crimson p-benzenesulfonic acid-azo-α-naphthylamine with an absorption maximum at 520 nm. The relationship between absorbance and concentration of methomyl is linear in the range 0.5–10 μg. The method is sensitive and specific; 0.625 ppm methomyl can be determined in a 40 g sample of selected vegetables, grains, and soil.
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