Pesticides characteristics

Table 1 Airborne pesticide characteristics and air sampling methods ...

The automated pesticide runoff model consists of a set of FORTRAN programs which calculate the amount of pesticide runoff from input of river basin data, rainfall data, pesticide characteristics, and application data. Table I shows the input requirements for the SWRRB model. Table II shows the output data from the SWRBB model. 

In order to produce the information needed for a hedonic analysis of the demand for pesticide characteristics (Soderqvist, Chapters, this volume), five properties of the herbicides, for which a continuous quantification was possible, have been selected price, persistence, action spectrum, reliability and toxicity. These properties cover approximately 10 out of 13 of the factors indicated in Table 2.5. Quantitative information for the five properties has been provided for the alternatives to atrazine, in order to provide input data for economic modelling (Soderqvist, Chapter 3, this volume). 

Laughlln, J., R.E. Gold, C.B. Easley and R.M. Hill. "Fabric Parameters and Pesticide Characteristics that Impact on Dermal Exposure of Applicators." NCRPIAP Project No. 170 (166-NC-NE-I). Unpublished progress reports and private communication 1982-1984. Orlando, J., D. Branson, G. Ayers, and M. Henry. "Development of Functional Apparel for the Reduction of Dermal Exposure to Pesticide Applicators." NCRPIAP Project Nos. 119/133/169 (34/136/165-NC-MI-I). Unpublished progress reports and private communication. 1980-1984. 

Exposure to pestieides poses a major hazard for agricultural workers. As a subset of chemical protective clothing, pesticide protective clothing has received much research attention. The effectiveness of the protective clothing is dependant on fabric properties, pesticide characteristics and the combination of both. 

Heterocyclics. One of the most characteristic and useful properties of hydrazine and its derivatives is the ability to form heterocycHc compounds. Numerous pharmaceuticals, pesticides, explosives, and dyes are based on these rings. A review of the appHcation of hydrazine in the synthesis of heterocychcs is available (91). For further information in the field of heterocycHc chemistry, see the General References. 

Biosensors ai e widely used to the detection of hazardous contaminants in foodstuffs, soil and fresh waters. Due to high sensitivity, simple design, low cost and real-time measurement mode biosensors ai e considered as an alternative to conventional analytical techniques, e.g. GC or HPLC. Although the sensitivity and selectivity of contaminant detection is mainly determined by a biological component, i.e. enzyme or antibodies, the biosensor performance can be efficiently controlled by the optimization of its assembly and working conditions. In this report, the prospects to the improvement of pesticide detection with cholinesterase sensors based on modified screen-printed electrodes are summarized. The following opportunities for the controlled improvement of analytical characteristics of anticholinesterase pesticides ai e discussed ... 

Pesticides vary widely in their chemical and physical characteristics and it is their solubility, mobility and rate of degradation which govern their potential to contaminate Controlled Waters. This, however, is not easy to predict under differing environmental conditions. Many modern pesticides are known to break down quickly in sunlight or in soil, but are more likely to persist if they reach groundwater because of reduced microbial activity, absence of light, and lower temperatures in the sub-surface zone. 

Skin is also important as an occupational exposure route. Lipid-soluble solvents often penetrate the skin, especially as a liquid. Not only solvents, but also many pesticides are, in fact, preferentially absorbed into the body through the skin. The ease of penetration depends on the molecular size of the compound, and the characteristics of the skin, in addition to the lipid solubility and polarity of the compounds. Absorption of chemicals is especially effective in such areas of the skin as the face and scrotum. Even though solid materials do not usually readily penetrate the skin, there are exceptions (e.g., benzo(Lt)pyrene and chlorophenols) to this rule. 

Pesticide use was not Carson s chosen topic. She preferred to author works that simply fostered a deeper appreciation of nature. A shy and soft-spoken woman, Carson wrote with an Albert Schweitzer-like reverence for life. All was sacred to her. Her style was lyrical, vivid, and romantic, falling mostly within the nature-writing tradition. She gave her creatures anthropomorphic characteristics, set them in dramatic situations, hoping, she said, to make animals in the woods or waters, where they live, as alive to others as they are to me. ... 

Dihexyl sulfosuccinate is used to improve the wetting and spreading characteristics of water-soluble pesticide sprays. In liquid fertilizers, insecticides, and fungicides, dioctyl sulfosuccinate will increase their penetrating ability. 

Leonas KK, Easter EP, Dejonge JO. 1989. Effect of fabric characteristics on pesticide penetration through selected apparel fabrics. Bull Environ Contam Toxicol 43 231-238. 

Reich GA, Gallaher GL, Wiseman JS. 1968. Characteristics of pesticide poisoning in south Texas. 

Baatrup, E. and Junge, M. (2001). Antiandrogenic pesticides disrupt sexual characteristics in the adult male guppy (Poecilia reticulata). Environmental Health Perspectives 109, 1063-1070. 

Test sites are selected from areas with different environmental and cultural conditions that might affect the levels of pesticide residues (e.g., temperature, soil characteristics, planting patterns). 

The determination of LOD and/or LOQ is not officially required. In a ring test of more than 10 laboratories initiated in 1992 by the Society of German Chemists [Gesellschaft Deutscher Chemiker (GDCh)] it was shown that these characteristics differ between laboratories by about one order of magnitude, even if the same pesticides are determined in similar matrices with the same method and calculation of the LOD or LOQ is performed in an identical way. 

If analytical methods are validated in inter-laboratory validation studies, documentation should follow the requirements of the harmonized protocol of lUPAC. " However, multi-matrix/multi-residue methods are applicable to hundreds of pesticides in dozens of commodities and have to be validated at several concentration levels. Any complete documentation of validation results is impossible in that case. Some performance characteristics, e.g., the specificity of analyte detection, an appropriate calibration range and sufficient detection sensitivity, are prerequisites for the determination of acceptable trueness and precision and their publication is less important. The LOD and LOQ depend on special instmmentation, analysts involved, time, batches of chemicals, etc., and cannot easily be reproduced. Therefore, these characteristics are less important. A practical, frequently applied alternative is the publication only of trueness (most often in terms of recovery) and precision for each analyte at each level. No consensus seems to exist as to whether these analyte-parameter sets should be documented, e.g., separately for each commodity or accumulated for all experiments done with the same analyte. In the latter case, the applicability of methods with regard to commodities can be documented in separate tables without performance characteristics. 

As a result of this dilemma, examples of all kinds of documentation exist in official method collections. At the simplest level, it starts with the presentation of tables containing (a) the pesticides and (b) the matrices which can be analyzed, but without any performance characteristics. The most complete documentation is found in the Swedish manual, where the number of experiments, the mean recovery and its range and the RSD are listed separately for each pesticide-matrix-level combination. ... 

Climatic fluctuations, long-term usage trends and agronomic practices can dramatically affect the characteristics of the monitoring data obtained from a field study, and this in turn affects the degree to which the study can be utilized to generalize about the environmental impacts of use of the pesticide. Surface water programs should be multi-year studies if one intends to address adequately the variability of pesticide... 

Technology providers use quantitative immunoassays to determine expression data of field material for regulatory submissions. Regulatory authorities require that expression levels of introduced proteins in various plant parts be determined by quantitative, validated methods. Immunoassays are also used to generate product characterization data, to assess food, feed and environmental characteristics, to calculate concentrations for toxicology studies and to obtain tolerance exemption or establish tolerances for pesticidal proteins. 

The concept of SPME was first introduced by Belardi and Pawliszyn in 1989. A fiber (usually fused silica) which has been coated on the outside with a suitable polymer sorbent (e.g., polydimethylsiloxane) is dipped into the headspace above the sample or directly into the liquid sample. The pesticides are partitioned from the sample into the sorbent and an equilibrium between the gas or liquid and the sorbent is established. The analytes are thermally desorbed in a GC injector or liquid desorbed in a liquid chromatography (LC) injector. The autosampler has to be specially modified for SPME but otherwise the technique is simple to use, rapid, inexpensive and solvent free. Optimization of the procedure will involve the correct choice of phase, extraction time, ionic strength of the extraction step, temperature and the time and temperature of the desorption step. According to the chemical characteristics of the pesticides determined, the extraction efficiency is often influenced by the sample matrix and pH. 

As with GC/MS, LC/MS offers the possibility of unequivocal confirmation of analyte identity and accurate quantiation. Similarly, both quadrupole and ion-trap instruments are commercially available. However, the responses of different analytes are extremely dependent on the type of interface used to remove the mobile phase and to introduce the target analytes into the mass spectrometer. For pesticide residue analyses, the most popular interfaces are electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). Both negative and positive ionization can be used as applicable to produce characteristically abundant ions. 

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