Herbicide extraction

Compound-pesticides and herbicides Extractant Clean-up Analytical finish Reference... 

Triazine herbicide Extraction method Comments Reference... 

Methanol can be used instead of diazomethane for esterification of herbicides. The reaction is catalyzed by BF3. To 1 mL of herbicide extract, add an equal amount of toluene or benzene. This is followed by 1 mL of BF3-methanol. The solution is heated in a water bath for a few minutes. Ether evaporates out. Addition of a few milliliters of water partitions unreacted methanol and BF3 into the aqueous phase, while the methyl esters of herbicides remain in the upper layer of benzene or toluene. The extraction steps discussed above are summarized in the following schematic diagram. 

MAJOR USES Used in the manufacture of phosphate, coumarin, salicylaldehyde, disinfectants, solvents, resins, scouring agents, herbicides extraction of ore. 

The FDA has pubhshed methods for the deterrnination of residual solvents in spice extracts such as oleoresins and has limited the concentrations of those specific solvents that are permitted. Chlorinated hydrocarbons and benzene have been almost completely removed from use as extracting solvents in the United States their use continues overseas where toxicity regulations are less stringent. The presence of pesticides or herbicides in spices is rigidly controHed by the FDA. 

Preparation of soil—sediment of water samples for herbicide analysis generally has consisted of solvent extraction of the sample, followed by cleanup of the extract through Uquid—Uquid or column chromatography, and finally, concentration through evaporation (285). This complex but necessary series of procedures is time-consuming and is responsible for the high cost of herbicide analyses. The advent of soUd-phase extraction techniques in which the sample is simultaneously cleaned up and concentrated has condensed these steps and thus gready simplified sample preparation (286). 

Supercritical CO2 has also beea tested as a solveat for the removal of organic contaminants from sod. At 60°C and 41.4 MPa (6,000 psi), more than 95% of contaminants, such as diesel fuel and polychlotinated biphenyls (PCBs), may be removed from sod samples (77). Supercritical CO2 can also extract from sod the foUowiag hydrocarbons, polyaromatic hydrocarbons, chlotinated hydrocarbons, phenols, chlotinated phenols, and many pesticides (qv) and herbicides (qv). Sometimes a cosolvent is required for extracting the more polar contaminants (78). 

An on-line concentration, isolation, and Hquid chromatographic separation method for the analysis of trace organics in natural waters has been described (63). Concentration and isolation are accompHshed with two precolumns connected in series the first acts as a filter for removal of interferences the second actually concentrates target solutes. The technique is appHcable even if no selective sorbent is available for the specific analyte of interest. Detection limits of less than 0.1 ppb were achieved for polar herbicides (qv) in the chlorotriazine and phenylurea classes. A novel method for deterrnination of tetracyclines in animal tissues and fluids was developed with sample extraction and cleanup based on tendency of tetracyclines to chelate with divalent metal ions (64). The metal chelate affinity precolumn was connected on-line to reversed-phase hplc column, and detection limits for several different tetracyclines in a variety of matrices were in the 10—50 ppb range. 

The development of methods of analysis of tria2ines and thek hydroxy metabohtes in humic soil samples with combined chromatographic and ms techniques has been described (78). A two-way approach was used for separating interfering humic substances and for performing stmctural elucidation of the herbicide traces. Humic samples were extracted by supercritical fluid extraction and analy2ed by both hplc/particle beam ms and a new ms/ms method. The new ms /ms unit was of the tandem sector field-time-of-flight/ms type. 

A multiresidue analytical method based on sohd-phase extraction enrichment combined with ce has been reported to isolate, recover, and quantitate three sulfonylurea herbicides (chlorsulfuron, chlorimuron, and metasulfuron) from soil samples (105). Optimi2ation for ce separation was achieved using an overlapping resolution map scheme. The recovery of each herbicide was >80% and the limit of detection was 10 ppb (see Soil chemistry of pesticides). 

Aroclor 1248, Aroclor 1254, and Aroclor 1260. Quantitation is by comparison of chromatograms with standard concentrations of pure compounds treated in an identical manner. The phenoxy acid herbicides (2,4-dichlorophenoxy)acetic acid (2,4-D), sUvex, and (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) can be deterrnined by electron-capture detection after extraction and conversion to the methyl esters with BF.-methanol. The water sample must be acidified to pH <2 prior to extraction with chloroform. 

Phenylurea herbicides (urons). Dinocap, Dinoseb, Benomyl, Carbendazim and Metamitron in Waters [e.g. determination of phenylurea herbicides by reverse phase HPLC, phenylurea herbicides by dichloromethane extraction, determination by GC/NPD, phenylurea herbicides by thermospray LC-MS, Dinocap by HPLC, Dinoseb water by HPLC, Carbendazim and Benomyl (as Carbendazim) by HPLC], 1994... 

Figure 13.11 Column-switcliing RPLC trace of a surface water sample spiked with eight chlorophenoxyacid herbicides at the 0.5 p-g 1 level 1, 2,4-dichlorophenoxyacetic acid 2, 4-chloro-2-methylphenoxyacetic acid 3, 2-(2,4-diclilorophenoxy) propanoic acid 4, 2-(4-cliloro-2-methylphenoxy) propanoic acid 5, 2,4,5-trichlorophenoxyacetic acid 6, 4-(2,4-dichlorophenoxy) butanoic acid 7, 4-(4-chloro-2-methylphenoxy) butanoic acid 8, 2-(2,4,5-tiichlorophenoxy) propionic acid. Reprinted from Analytica Chimica Acta, 283, J. V. Sancho-Llopis et al., Rapid method for the determination of eight chlorophenoxy acid residues in environmental water samples using off-line solid-phase extraction and on-line selective precolumn switcliing , pp. 287-296, copyright 1993, with permission from Elsevier Science.

The two examples of sample preparation for the analysis of trace material in liquid matrixes are typical of those met in the analytical laboratory. They are dealt with in two quite different ways one uses the now well established cartridge extraction technique which is the most common the other uses a unique type of stationary phase which separates simultaneously on two different principles. Firstly, due to its design it can exclude large molecules from the interacting surface secondly, small molecules that can penetrate to the retentive surface can be separated by dispersive interactions. The two examples given will be the determination of trimethoprim in blood serum and the determination of herbicides in pond water. 

This analysis depends on the use of a solid phase extraction cartridge to concentrate the herbicides directly from the pond water and the... 

EPA. 1997e. Methods and guidance for analysis of water. Method 508.1 Determination of chlorinated pesticides, herbicides, and organohalides by liquid-solid extraction and electron capture gas chromatography. U.S. Environmental Protection Agency, Washington, DC. EPA 821-C-97-001. 

Uses Chlorine is used for water purification and in decreasing amounts for pulp and paper bleaching. Some is used for metallurgical purposes such as metal extraction. Its largest use is for the production of organic compounds used in plastics, pesticides, herbicides, refrigeration fluids, solvents, and others. 

Only the R(+) enantiomer of the herbicide 2-(2-methyl-4-chlorophenoxy)propionic acid was degraded (Tett et al. 1994), although cell extracts of Sphingomonas herbicidovorans grown with the R(-) or S -) enantiomer, respectively, transformed selectively the R -) or S(-) substrates to 2-methyl-4-chlorophenol (Nickel et al. 1997). 

This was previously used as a herbicide, and attention has been directed to its degradation in storage areas or where it has been spilled. A strain of Clostridium bifermentans KMR-1 (that is protected by a U.S. patent) was unable to use dinoseb as carbon or energy source. In the presence of a starch extract, however, a low level of transformation was observed, and the products could subsequently be mineralized by aerobic bacteria (Hammill and Crawford 1996). These observations have been extended to the remediation of soil slurries from a contaminated site by adding phosphate and starch waste that achieved anaerobic conditions, and inoculation with a culture from a pilot-scale... 

Amines are important industrial chemicals which are involved in everyday life [3, 4]. Apart from the usual classification into primary, secondary, and tertiary amines, the distinction is often made between lighf amines (less than six-carbon substituents) and fatty amines. light amines are intermediates for the synthesis of drugs, herbicides, cosmetics, etc. [3]. They also find use as vulcanization accelerators and extraction agents. Fatty amines are involved in the synthesis of corrosion inhibitors and cationic surfactants, which are used in ore flotation processes and are good fabric softeners and antistatic agents [4—6],... 

The rationale of validation experiments with fatty matrices is the high amount of fat extracted with many organic solvents. If analytes are not fat soluble and extraction is performed with water or aqueous buffer solutions, the troublesome fat is not extracted together with the analyte. Such extractions are typical for, e.g., the class of sulfonylurea herbicides. Examples exist where in such cases the applicability of an analytical method to fatty matrices was accepted by the authority without particular validation. 

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... 

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