Soil residue analytical methods

Annex VI to Directive 91/414/EEC concerning the placing of plant protection products on the market. The section concerning residue analytical methods was not fully finalized when the Directive was first adopted. There were no provisions for methods to determine residues from a.i. and relevant metabolites in soil, water, and air. The criteria for foodstuffs partly proved to be not helpful for the practice of assessment (e.g., with regard to reproducibility, ISO 5725 requires validation in at least eight independent laboratories). 

Multi-residue analytical method for the determination of acetochlor, alachlor, and metolachlor soil metaholites in aqueous samples... 

A The Multi-residue analytical method is provided for plant, soil and water samples. 

All of the compounds (pyraflufen-ethyl and its metabolites) are converted to E-2 and quantified as the total toxic residue of pyraflufen-ethyl. The conversion to E-2 is carried out by oxidative decomposition with concentrated sulfuric acid. The reaction mixture is extracted with a solvent and subjected to simple cleanup, followed by GC/NPD analysis. This method is rapid and simple compared with the Multi-residue analytical method , and has wide applicability to different varieties of the samples, such as plant materials, soils and water, with only minor adjustment of the analytical method. 

H. Matsushita, T. Oishi, Y. Asano, and K. Ishikawa, Residue analytical method of pyrithiobac-sodium in crops and soil, in Abstracts of the 17th Annual Meeting of the Pesticide Science Society of Japan, p. 149 (1992). 

Residue analytical methods for neonicotinoids in crops, soil and water samples have been developed. The basic principle of these methods consists of the following steps extraction of the crop and/or soil samples with acetone or the other organic solvent, cleanup by liquid-liquid partition or column chromatography, and quantitative analysis by high-performance liquid chromatography with ultraviolet detection (HPLC/UV). Simple column cleanup procedures are used to improve the accuracy and sensitivity of these methods. 

Four different types of residue analytical methods of flutolanil and its metabolites are developed for plant (potato and rice), soil and water ... 

Buprofezin and its metabolites, p-OH-buprofezin and BF12, are hydrophobic under neutral conditions. Having the organic base part in their chemical structure, these compounds form water-soluble salts under strongly acidic conditions. The change in solubilities of these compounds influences the cleanup procedure. Four different residue analytical methods have been developed to measure buprofezin and its metabolites in plants (rice, citrus and tomato cucumber, pepper, tomato, squash and eggplant), soil and water ... 

C Multi-residue analytical method (for soil) determines buprofezin and BF12 in soil sample simultaneously using GC/NPD. 

Multi-residue analytical method (for plant and soil) is provided for plants (apple, grape etc.) and soil samples. After GPC cleanup, fenpyroximate and M-1 are analyzed simultaneously using gas chromatography (GC)/NPD. 

For certain naturally occurring nontoxic a.i., an enforcement is not sensible (e.g., lecithin, rape seed oil). Analytical methods for residues in soil are not necessary if the DTgo values of the a.i. and relevant metabolites are less than 3 days (e.g., fosetyl), because in general, the results from residue analyses are not meaningful if the a.i. is rapidly degraded. 

Chloroacetanilides are soil-applied herbicides used for pre- and early post-emergence control of annual grasses and broadleaf weeds in crops. Representative chloroacetanilide compounds, alachlor, acetochlor, and metolachlor, are extensively used worldwide. Other chloroacetanilides with limited usages include propachlor, bu-tachlor, metazachlor, pretilachlor, and thenylchlor. Public environmental concerns and government regulatory requirements continue to prompt the need for reliable methods to determine residues of these herbicides. There now exist a variety of analytical methods to determine residues of these compounds in crops, animal products, soil, and water. The chemical structures and major crops in which these compounds are used are summarized in Table 1. 

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

Soil samples are extracted with buffered acetonitrile with a mechanical shaker. Alter centrifuging, aliquots of the extracts are amended with isotopically labeled internal standards and evaporated to dryness. The samples are reconstituted and analyzed by LC/MS/MS. This method determines soil residues of flucarbazone-sodium, sulfonic acid, sulfonamide and NODT with an LOQ of 0.001 mg kg for each analyte. 

The ECL evaluates analytical methods for detecting pesticide residues in the environment to ensure that the methods are suitable for monitoring pesticide residues in soil and water. State, tribal and federal laboratories may access an Index of Environmental Chemistry Methods for a list of available methods. The ECL also provides the State pesticide laboratories with technical and QA support and training in pesticide analytical chemistry. 

As more sensitive analytical methods for pesticides are developed, greater care must be taken to avoid sample contamination and misidentification of residues. For example, in pesticide leaching or field dissipation studies, small amounts of surface soil coming in contact with soil core or soil pore water samples taken from further below the ground surface can sometimes lead to wildly inaccurate analytical results. This is probably the cause of isolated, high-level detections of pesticides in the lower part of the vadose zone or in groundwater in samples taken soon after application when other data (weather, soil permeability determinations and other pesticide or tracer analytical results) imply that such results are highly improbable. 

It is a regulatory requirement that analytical methods be developed to determine residues of concern in crops, feed, and food commodities as well as environmental samples (air, soil, and water). Methods for crops, feed, and food commodities are required for enforcement purposes but are also needed for a variety of other purposes, such as gathering monitoring data for risk assessment. For nearly any purpose, the methods must be robust, that is, when used by different analysts in several laboratories, they should provide reproducibly similar results. 

Organic solvent extraction. Two analytical methods for acetamiprid have been developed One method is for the parent only and the other determines the total residue of the parent and its metabolites (lM-1-2, lM-1-4 and lC-0). Air-dried soil (20-g equivalent dry soil) is weighed into a centrifuge tube and imidacloprid residue is extracted with 100 mL of methanol-0.1M ammonium chloride (4 1, v/v) using a mechanical shaker for about 30 min. After shaking, the tube is centrifuged at 8000 rpm for 2 min. The supernatant is filtered and the analysis of the soil residue is carried out in the same manner as described above for the parent compound. 

Excavations were completed in summer 2002. The residues to be excavated were classified by on-site analytical methods, and were temporarily stored on-site for later off-site disposal. Soil sampling at the site showed that the highest level of contamination was found, as expected, in the area surrounding the former inlet of the pond. However, during excavation, a second hot spot was found with TNT concentrations of several g/kg TNT. Thus more soil had to be excavated than was initially expected. The TNT was concentrated in clayey soil. 

Army. 1987a. Development of an analytical method for explosives residues in soil. Aberdeen Proving Ground, MD U.S. Army Toxic and Hazardous Materials Agency. Document no. AD A183738. 

In the United States, approval of new herbicides depended not only on performance and toxicity data, but also on a clear picture of eventual crop and soil residues. The Geigy Analytical Department began immediately to develop a reliable residue method for simazine and other triazines. Working methods for residues in plants and soil were available by the end of 1956. 

Yokley, R.A., L.C. Mayer, R. Rezaaiyan, M.E. Manuli, and M.W. Cheung (2000). Analytical method for the determination of cyro-mazine and melamine residues in soil using LC-UV and GC-MSD../. Agric. Food Chem., 48 3352-3358. 

Tables II and III show that downward leaching of DDT and its analogs is very slow, with less than 3% of the total residue having penetrated below the 1-foot level. The amount of o,p-DDT, p,p-DDE, and p,p-TDE [l,l-dichloro-2,2-bis(parachlorophenyl)ethane] present is expressed as a ratio with p,p-DDT in order to relatfe the soil concentrations of these analogs with their concentrations in the technical DDT originally applied. The p,p-DDT to o,p-DDT ratios range from 7 to 14 at the various soil depths analyzed, while in technical DDT the ratio is about 3. This change in relative concentration suggests that the o,p-isomer is less persistent in soil. This result is contrary to that of Woodwell and Martin (11) who found more o,p-isomer in the surface layers of forest soils exposed to DDT. The analytical methods used by these authors are not as reliable as those described here, however.

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