Persistence of the insecticide Dimilin 45 ODC on conifer forest foliage in an Atlantic-climate ecosystem.

The oil formulation of diflubenzuron (Dimilin 45 ODC) persisted for 10-12 weeks on the foliage of a conifer forest in an Atlantic-climate ecosystem. Within 22-30 days following treatment, 55-80% of the insecticide had been removed from the foliage. During this period, the concentration of diflubenzuron was higher than 370 ng g(-1). Aerial application at 56.3 g of Al ha(-1) resulted in deposition levels of the insecticide ranging from 867.5 to 1824.4 ng g(-1), depending upon forest characteristics. The results showed that aerial application is only a suitable technique for the treatment of forest areas with dense foliage and/or high tree density and no more than 15% of tree-free area. The only metabolite detected was 2,6-difluorobenzamide, and this persisted on foliage until the first rainfalls occurred. An empirical mathematical correlation was found to express the influence of meteorological variables--rainfall, solar radiation and temperature--on the persistence of the insecticide. These results suggested that degradation of diflubenzuron on foliage could be due to photodegradation. Some recommendations were made to optimize the deposition of the insecticide on foliage and to minimize its persistence and the off-site spray drift.

Solid-phase microextraction for the determination of systemic and non-volatile pesticides in river water using gas chromatography with nitrogen-phosphorous and electron-capture detection.

A solid-phase microextraction (SPME) method combined with gas chromatography with nitrogen-phosphorous and electron capture detection for the analysis of the pesticides terbumeton, metribuzine, isomethiozine, pyridafenthion and triadimenol in river water has been developed. For this purpose, polyacrylate and polydimethylsiloxane coated fibres have been utilised and the factors affecting throughput, precision and accuracy of the SPME method have been investigated and optimised. These factors include: matrix influence, adsorption time, pH, salt effect, desorption time, temperature and also the lapse of time between sampling and injection. The performed analytical procedure showed detectability ranging from 2.0 ng l(-1) to 3.0 microg l(-1) and precision from 1.9 to 27.7% (as relative standard deviation) depending on the pesticide, the fibre and the detector used. The results demonstrate the suitability of the SPME method to analyse these non-volatile pesticides in river water.

Determination of the insecticide pyridafenthion in river water, soils and wine by adsorptive stripping voltammetry.

Solid-phase extraction or liquid-liquid extraction has been combined with adsorptive stripping voltammetry at a hanging mercury drop electrode to isolate, determine, quantify and recover trace concentrations of pyridafenthion in water, wine and soil. A systematic study of the experimental parameters affecting the stripping response was carried out by differential pulse voltammetry. By using an accumulation potential of 400 mV and an accumulation time of 540 s, the limit of detection was 0.17 microgram l-1 and the relative standard deviation (n = 10) was 1.9% at a concentration level of 8.5 micrograms l-1. Different methods are proposed which eliminate matrix interferences. These results have been applied to the systematic study of this compound in water, wine and soil. The lowest detectable concentration for pyridafenthion is 34 micrograms l-1 in water, 102 micrograms l-1 in wine and 80 micrograms kg-1 in soil. Recoveries of the pyridafenthion from supplied environmental samples were in all cases higher than 92% with a relative standard deviation lower than 3%.

Joint determination of todralazine and acetazolamide in human serum by differential pulse polarography.

Differential pulse polarography (DPP) is proposed as a direct method for the quantitation of todralazine and acetazolamide in human serum. The method was applied to the determination of these drugs in human serum, after a liquid-liquid extraction process. This extraction process together with the use of the standard additions method is essential for the elimination of the matrix effect. The proposed method enables detection limits of 0.107 microgram ml-1 for acetazolamide and 0.111 microgram ml-1 for todralazine to be achieved at reduction potentials of -0.59 and -0.86 V, respectively, using Britton-Robinson buffer (pH 1.65) as the supporting electrolyte.