Pesticides, mineral tests

In the adsorption with Tenax alone satisfactory results were obtained, while in the presence of mineral oil a considerable proportion of the organophos-phorus pesticides (particularly Malathion and Parathion-methyl) was not adsorbed and was recovered in the filtered water. This drawback can be overcome by adding a layer of Celite 545 which, in order to prevent blocking of the column, is mixed with silanised glass wool plugs. A number of analyses of surface and estuarine sea waters were carried out by this modified Tenax column and simultaneously by the liquid-liquid extraction technique. To some of the samples taken, standard mixtures of pesticides were also added, each at the level of 1 xg/l (i.e., in concentration from 13 to 500 times higher than that usually found in the waters analysed). One recovery trial also specifically concerned polychlorobiphenyls. The results obtained in these tests show that the two extraction methods, when applied to surface waters that were not filtered before extraction, yielded very similar results for many insecticides, with the exception of compounds of the DDT series, for which discordant results were frequently obtained. 

In a majority of instances, particularly with pesticides, combinations of chemicals (e.g., organic solvents, mineral oils) are mixed to enhance the chemical toxicity. Consequently, the toxicity profile is altered. Lipophilicity modulates the absorption rate of the chemical from the site of entry into the system (lung, skin, mucous membrane). Thus, the fat-solubility pattern of a test chemical helps for easy cell membrane transport to reach the active site of intracellular enzymes and trigger possible toxic effects. The toxicity profile of active ingredients of pesticides and those of formulated products of pesticides differ widely. 

Comprehensive mineral water analysis or medicinal water analysis. In this analysis, all substances contained in the water should be determined, as far as they are qualitatively detectable and quantitatively recordable according to the latest advances in analytical chemistry. Tests should also be made to see whether anthropogenic substances, such as halocarbons, pesticides, etc., can be detected in the trace range. In addition, bacteriological investigations, tests for radioactivity and, where applicable, radiochemical analyses and gas analyses are necessary. 

A vast number of synthetic organic pollutants, including pesticides, dyestuffs, pharmaceutical and personal care products (PPCPs), and commonly used industrial chemicals, are routinely discharged into water streams. In agreement with the precautionary principle that aims to protect the natural resources from potential contamination, a broad set of water treatment technologies has been devised and tested in recent years. The compared mineralization ability of several EAOPs discussed above is depicted in Fig. 2. 

Since the pesticide industry consumes only a minor fraction of mineral output in the United States pesticide formulators make use of standard grades of minerals produced for other industries. For the same reason, pesticide formulators apply industry standard tests when evaluation of minerals is required. Except in imusual circumstances only three properties of a mineral will be of significance - liquid holding capacity, bulk density, and surface pH (McKay, 1979 Weidhaas, 1955). 

Evaluation of mineral products for pesticide formulation purposes will make use of tests designed and recommended by suppliers (Floridin, Engelhard, Edward Lowe). 

Chemical Stability - The most critical test for an end-use product is chemical stability of the pesticide active ingredient. Evaluation of chemical stability does not depend on any particular property of a mineral carrier or solid diluent. Evaluations are carried out by asking whether active ingredient is stable in the end-use formulation for a certain length of time under certain storage conditions. Answering the question makes use only of a chemical analysis for active ingredient, and is essentially independent of any property of the mineral. 

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