Silver nanoparticle-modified electrode for the determination of nitro compound-containing pesticides.

This paper reports the electroanalytical determination of pendimethalin and ethyl parathion by square-wave adsorptive stripping voltammetry using a material comprised of chitosan-stabilized silver nanoparticles to modify a glassy carbon electrode. Under optimized experimental conditions, the peak current was found to vary linearly with the concentration of pendimethalin in the range of 70 to 2000 nmol L(-1) and with concentration of ethyl parathion in the range of 40 to 8000 nmol L(-1). Detection limits of 36 and 40 nmol L(-1) were obtained for pendimethalin and ethyl parathion, respectively. The silver - nanoparticle-modified electrode was successfully employed for the analysis of pesticides in tap and mineral water (pendimethalin) and in lettuce and honey (ethyl parathion) samples. Pendimethalin recovery was between 94 and 100 %, and ethyl parathion recovery was between 97 and 101 %, indicating no significant matrix interference effects on the analytical results. The accuracy of the electroanalytical methodology using the proposed modified electrode was also compared to that of the UV-vis spectrophotometric method.

Environmentally-friendly in situ plated bismuth-film electrode for the quantification of the endocrine disruptor parathion in skimmed milk.

An in situ bismuth-film electrode (BiFE) together with square-wave cathodic voltammetry (SWCV) was used to determine the concentration of the endocrine disruptor parathion in skimmed milk. The experimental conditions (deposition time, deposition potential and Bi (III) concentration) were optimized for the preparation of the BiFE. A glassy carbon electrode was used as the substrate. The selection of the chemical composition of the supporting electrolyte and the solution pH was aimed at improving the reduction of parathion at the BiFE surface. In addition, the parameters of the square-wave cathodic voltammetry were adjusted to improve the sensor performance. A cathodic current identified at -0.523 V increased linearly with the parathion concentration in the range of 0.2-2.0 µmol L(-1) (R=0.999). The sensitivity of the calibration curve obtained was 4.09 µA L µmol(-1), and the limits of detection (LOD) and quantification (LOQ) were 55.7 nmol L(-1) and 169.0 nmol L(-1), respectively. The performance of the sensor was tested using a sample of skimmed milk with parathion added. The same determination was carried out by UV-vis spectroscopy and the results obtained were used for the statistical evaluation of the data obtained.

[Degradation of the insecticide parathion in soil]. / Degradação do inseticida paration em solos.

Degradation of the insecticide Parathion in four types of soil from the Northeast of Brazil has been studied using radiometric techniques. In all the soil samples, sterilized or not, metabolites were detected with Rf values of 0.00 and 0.17 respectively--Silica Gel 60 F254 tlc plates (Merck); solvent system: hexane-acetone (4:1, v/v)--. However, 14CO2 was formed only with the non-sterilized soils and this was independent of the use or not of organic fertilizer. These results suggest that the two metabolites, mentioned above, are formed by a predominantly non-biological pathway, where as the formation of carbon dioxide requires the participation of the microbial flora of the soil. Analysis of the interaction of 14C-Parathion with soils shows that the extent of degradation of this insecticide is modified by adsorption on the soil particles.

Laboratory tests of the persistence of pesticides in two Brazilian soils.

The persistence of 5 insecticides in two soils, one rich (soil 1), the other poor (soil 2) in organic matter was examined in the laboratory using gas chromatographyc and radiometric techniques. About half DDT and aldrin were lost in 256 days. The other pesticides, in order of decreasing persistence were lindane, parathion (Table I) and malathion (Table II). Aldrin was converted to dieldrin faster in soil 1 than in soil 2. Parathion and lindane were both lost faster from soil 2 than from soil 1. In contrast, malathion was lost more slowly from soil 2 than soil 1, from which all disappeared in 4 days (Table II)

Sorption and movement of pesticides on thin layer plates of Brazilian soils.

The sorption from aqueous solution (Table II), and movement in water on thin layers plates (Figure 1) of 7 soils (Table 1) of 3 organochlorine, 2 organophosphorus and 1 carbamate insecticide was determined in the laboratory. Generally, all substances were sorbed most and moved least on soils richest in organic matter. However, sorption was not a function of organic matter content alone (Table III). Aldrin and DDT were most strongly sorbed and did not move from the point of application on the thin layer plates of any soil. On all 7 soils, carbaryl was the least strongly sorbed insecticide. On 5 soils, lindane, parathion and malathion were increasingly strongly sorbed, but on the other 2 soils lindane was mostly strongly sorbed. The apparent greater mobility of 14C-labelled malathion on thin layers of soils repeatedly leached could be explained by the formation of more polar substances.

Fatal parathion poisoning caused by contamination of flour in international commerce.

In January 1976, 79 persons in Jamaica were acutely poisoned by the organophosphorus insecticide parathion. Seventeen died. Cases occurred in three episodes at separate locations, but all patients had consumed wheat flour from a single lot consisting of 5264 cotton bags. Parathion in concentrations of less than 1 to 9900 ppm was identified in flour from six bags in this lot; three had splash marks. The flour had been milled in Western Europe from European wheat, carried in trucks to a dockside warehouse, and loaded aboard ship after 2-5 days' storage. In Jamaica, the flour had moved from quayside to outbreak locations along separate routes through two import houses. Site inspections and review of shipping records suggested that the likely point of contamination was the European port, where foodstuffs and insecticides were stored in the same warehouse.

Fatal parathion poisoning caused by contamination of flour in international commerce

In January 1976, 79 persons in Jamaica were acutely poisoned by the organophosphorous insecticide parathion. Seventeen died. Cases occurred in three episodes at separate locations, but all patients had consumed wheat flour from a single lot consisting of 5264 cotton bags. Parathion in concentrations of <1 to 9900 ppm was identified in flour from six bags in this lot: three had splash marks. The flour had been milled in Wertern Europe from European wheat, carried in trucks to a dockside warehouse, and loaded aboard ship after 2-5 days' storage. In Jamaica, the flour had moved from quayside to outbreak locations along separate routes through two import houses. Site inspections and review of shipping records suggested that the likely point of contamination was the European port, where foodstuffs and insectisides were stored in the same warehouse (AU)