Hydrophiles pesticides

Residue analytical chemistry has extended its scope in recent decades from the simple analysis of chlorinated, lipophilic, nonpolar, persistent insecticides - analyzed in the first Si02 fraction after the all-destroying sulfuric acid cleanup by a gas chro-matography/electron capture detection (GC/ECD) method that was sometimes too sensitive to provide linearity beyond the required final concentration - to the monitoring of polar, even ionic, hydrophilic pesticides with structures giving the chemist no useful feature other than the molecule itself, hopefully to be ionized and fragmented for MS or MS" detection. 

Grissom, R.E., Jr. C. Brownie, and F.E. Guthrie. 1987. In vivo and in vitro dermal penetration of lipophilic and hydrophilic pesticides in mice. Bull. Environ. Contam. Toxicol. 38 917-924. 

Low levels of an applied herbicide-pesticide-solvent mix were drawn into the uptake air of a commercial building following the application of a pesticide mix to the lawn in front of that building. Several employees immediately reported CNS and respiratory symptoms, with one sustaining a permanent respiratory injury. The pesticide mix applied to the lawn was composed of 2,4-D (2.82), 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP 2.48), and dicamba (2.21). The mixture also contained solvent naphtha (a mixture of aliphatic solvents, Kqw = 3.5-5.0) with 14% naphthalene (2.48) and dinitroaniline (3.30). The concentrations of all pesticides and solvents were far below the TLVs both outside and inside the building. The toxic effects observed were ascribed to the mixture of lipophilic and hydrophilic pesticides. 441... 

Chronic peripheral nervous system effects have been reported in farmers who applied the organophosphate pesticides methyl parathion (2.86), azinphos-methyl (2.75), and tetraethylpyrophosphate (0.45) pesticides in xylene (3.15) solutions and were exposed to levels below those known to produce acute or subacute symptoms. Similar effects were described in another study of low level exposure to organophosphate pesticidesJ49l In both cases, it is hypothesized that the lipophilic solvent (xylene) facilitated the absorption of greater than expected quantities of the more hydrophilic pesticides. 441... 

Despite a 3-fold range in follicle area in the marmoset, no differences in absorption rates of paraquat, mannitol, water, and ethanol were observed between different body sites (Scoll et al., 1991). However, among the different species examined in this study, there was an 80-fold range in follicle area, which correlated with observed differences in the rate of mannitol and paraquat absorption. The authors concluded that this correlation was only possible with relatively slowly ab.sorbed le.st penetrants, such as paraquat and mannitol. Further work is needed to determine to what extent unique anatomical features at different body sites play a role in absorption and penetration of both lipophilic and hydrophilic pesticides. 

The more hydrophilic pesticides, such as organophosphorus (OPs), have a log value of less than 3, and as a result tend to be excreted by urine and... 

Relatively hydrophilic pesticides are especially interesting insofar as they can penetrate into sieve tubes and be submitted to phloem transport (organophosphorus insecticides, glyphosate...). 

RH above can represent a very wide variety of xenobi-otics, including drugs, carcinogens, pesticides, petroleum products, and pollutants (such as a mixture of PCBs). In addition, endogenous compounds, such as certain steroids, eicosanoids, fatty acids, and retinoids, are also substrates. The substrates are generally lipophilic and are rendered more hydrophilic by hydroxy-lation. 

Is this compound hydrophilic or hydrophobic Do animals excrete DDT readily, or will the compound concentrate in fatty tissues Does your answer explain why DDT has been banned as a pesticide ... 

The design and implementation of a portable fiber-optic cholinesterase biosensor for the detection and determination of pesticides carbaryl and dichlorvos was presented by Andreou81. The sensing bioactive material was a three-layer sandwich. The enzyme cholinesterase was immobilized on the outer layer, consisting of hydrophilic modified polyvinylidenefluoride membrane. The membrane was in contact with an intermediate sol-gel layer that incorporated bromocresol purple, deposited on an inner disk. The sensor operated in a static mode at room temperature and the rate of the inhibited reaction served as an analytical signal. This method was successfully applied to the direct analysis of natural water samples (detection and determination of these pesticides), without sample pretreatment, and since the biosensor setup is fully portable (in a small case), it is suitable for in-field use. 

Historically, organic environmental pollutants were hydrophobic, often persistent, neutral compounds. As a consequence, these substances were readily sorbed by particles and soluble in lipids. In modern times, efforts have been made to make xenobiotics more hydrophilic - often by including ionisable substituents. Presumably, these functional groups would render the compound less bioaccumulative. In particular, many pesticides and pharmaceuticals contain acidic or basic functions. However, studies on the fate and effect of organic environmental pollutants focus mainly on the neutral species [1], In the past, uptake into cells and sorption to biological membranes were often assumed to be only dependent on the neutral species. More recent studies that are reviewed in this chapter show that the ionic organic species play a role both for toxic effects and sorption of compounds to membranes. 

A water soluble liquid formulation (WSL) is prepared from pesticides that are highly water soluble. This is, by far, the simplest type of formulation. One distinct advantage of WSL s over other formulations is that the field spray dilutions are infinitely stable as true solutions. Pesticides that are hydrophilic and ionic, such as inorganic or organic metallic salts, often fall into this category. Unfortunately, only a small portion of all pesticides are adequately soluble in water. 

LC techniques are widely diffused for the determination of hydrophilic but not volatile and thermally unstable pesticides. Since the European Community Directive [68] indicates 0.1 pg L" as the concentration threshold level for a single pesticide in waters destined for human consumption, to quantify these concentration levels, suitable pre-concentration and extraction procedures must be generally performed prior to the HPLC determination. The extraction methods are based on LLE, MAE, on-line continuous flow liquid membrane extraction (CFLME), and mainly on SPE and SPME. Many SPE procedures are used the packing materials are graphitized carbon, ODS, styrene-divinylbenzene co-polymers, or selective phases based on immunoafflnity. The extraction can be performed on- and off-line, manually, or in a semi-automated way. 

The current libraiy of polyurethanes has some utility, and we will illustrate their uses with examples from our laboratory and from others. Currently, hydrophobic polyurethanes can be used to extract nonpolar pollutants, for example, from some pesticides. At the other end of the spectrum, hydrophilic polyurethanes can be used to extract sparingly soluble organic pollutants from groundwater. We will illustrate this with the extraction of methyl-tert-butylether. 

Environmental research interests have recently extended from persistent hydrophobic organic chemicals to more hydrophilic organic compounds. The latter include some polar pesticides, many pharmaceuticals and personal care products, microbial toxins, and endocrine disrupting compounds.4 Polar organic compounds are often present at low concentrations in the aquatic environment, which poses a problem for most conventional sampling and analytical procedures. Recently, considerable effort has been directed toward the development of extraction methods suitable for the preconcentration of polar organic compounds commonly found in water bodies. Many of these methods use... 

The second effect of water on evaporation, requiring only the presence of water, arises from the fact that many clay surfaces (and some organic ones) are strongly hydrophilic but also capable of adsorbing other molecules. The pesticide may therefore be held sufficiently strongly on a dry soil for its evaporation to be greatly reduced. When the soil is wetted, however, the stronger affinity of the water displaces the pesticide. 

Besides water and ions, other substances can also be adsorbed on both the external and internal surfaces. Since the surface of rocks and soils is strongly hydrophilic on a macroscopic scale, hydrophilic substances are more strongly adsorbed than hydrophobic substances. Some authors, however, say that the hydrophilic-hydrophobic character strongly varies on molecular scale. So the oxygen atoms next to the isomorphic substitutions are hydrophilic, while the oxygen atoms far from them are hydrophobic. The hydrophobic oxygen atoms are, for example, responsible for the adsorption of hydrophobic pesticides (Laird 2004). 

A moderately hydrophilic emulsifier and lubricant, is used as an emulsifier for solvents in pesticide carriers and metal cleaners. In the textile industry it is used in the formulation of specialty detergents and dyeing assistants. It is also used as an emulsifier for neatsfoot oil in leather fat liquoring and as a rewetting agent for paper. 

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