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Analysts are increasingly being required to evaluate the uncertainty associated with methods. Estimating the uncertainty of an analytical result is an essential part of quantitative analysis. This paper discusses the sources of uncertainty of chlorpyrifos determination by gas chromatography equipped with flame photometric detector (GC-FPD). The analysis was performed on HP-5 MS, 30 m x 0.32 mm capillary column with a 0.25 μm stationary film thickness using ultra pure nitrogen (99.9999 %) as a carrier gas at 25 psi constant pressure. The method has been optimized. Factors affecting quantization of chlorpyrifos such as injector temperature, carrier gas inlet pressure, air to hydrogen ratios and initial temperature program have been studied to get the best sensitivity, minimum delectability. The liner range of the detector was from 0.15 ng/ml to 1200 ppm, the minimum detection limit was 0.15 ng/ml and the relative standard deviation was 0.839.
Content available remote Activities of brain antioxidant enzymes, lipid and protein peroxidation
Organophosphate pesticides are known to induce oxidative stress and cause oxidative tissue damage, as has been reported in studies concerning acute and chronic intoxication with these compounds. Our objective was to investigate the activities of brain antioxidant enzymes and malonyldialdehyde, as well as the level of carbonyl groups, in rats sub-chronically intoxicated with chlorpyrifos at doses of 0.2, 2 and 5 mg per kg of body weight per day. It was found that chlorpyrifos induces change in brain antioxidant enzymes, such as superoxide dismutase, catalase and glutathione peroxidise, but to a different degree in comparison to proper control values; however, the elevated antioxidant enzymes activities failed to check lipid and protein peroxidation in the brains of rats. Thus, in sub-chronic intoxication with chlorpyrifos, as evidenced by increased level of malonyldialdehyde and carbonyl groups, oxidative stress is induced. Measurements of protein carbonyl groups appeared to give more consistent responses in the rats’ brains when compared to the malonyldialdehyde level after sub-chronic chlorpyrifos treatment.
Organophosphate compounds are nowadays the most frequently used pesticides. For these insecticides, the primary target is acetylcholinesterase and for this reason the main clinical effect of acute intoxication with organophosphate insecticides involves an irreversible inhibition of the activity of this enzyme. However, in the chronic or subchronic exposition oxidative stress has been reported as the main mechanism of its toxicity. The present study investigated the effect of three low doses (0.2, 2, 5 mg/kg bw) of chlorpyrifos for 14 or 28 days on serum liver enzymes and on oxidative stress parameters in the liver of rats. Chlorpyrifos treatment resulted in aminotransferases and alkaline phosphatase increase after 14 days (higher doses) and 28 days (all doses) treatment together with changes of antioxidative enzymes activities and reduced glutathione and malonyldialdehyde level in the liver. The enhancement of lipid peroxidation is temporary, reaching a peak after 14 days and decreasing after 28 days of treatment. Based on the experimental findings of this study the temporary liver injury caused by oxidative stress has been shown. The disturbances in the liver antioxidative status and increased liver membrane permeability may appear in case of doses near to the accepted human daily intake.
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