Chlorinated acid herbicides separation

The methyl esters can be also determined by GC-FID. Using a 30 m x 0.32 mm ID x 0.25 pm (film thickness) capillary column, such as DB-1701 or equivalent, the compounds can be adequately separated and detected by FID. The recommended carrier gas (helium) flow rate is 35 cm/s, while that of the makeup gas (nitrogen) is 30 cm/min. All of the listed herbicides may be analyzed within 25 min. The oven temperature is programmed between 50 and 260°C, while the detector and injector temperatures should be 300 and 250°C, respectively. The herbicides may alternatively converted into their trimethylsilyl esters and analyzed by GC-FID under the same conditions. FID, however, gives a lower response as compared with ECD. The detection level ranges from 50 to 100 ng. For quantitation, either the external standard or the internal standard method may be applied. Any chlorinated compound stable under the above analytical conditions, which produces a sharp peak in the same RT range without coeluting with any analyte, may be used as an internal standard for GC-ECD analysis. U.S. EPA Method 8151 refers the use of 4,4,-dibromooctafluorobiphenyl and 1,4-dichlorobenzene as internal standards. The quantitation results are expressed as acid equivalent of esters. If pure chlorophenoxy acid neat compounds are esterified and used for calibration, the results would determine the actual concentrations of herbicides in the sample. Alternatively, if required, the herbicide acids can be stoichiometrically calculated as follows from the concentration of their methyl esters determined in the analysis ... 

Uses Intermediate for synthesis of chemicals incl. isocyanates, carbamates, urethanes, pharmaceuticals prod, of polycarbonates (automotive uses), pesticides, herbicides, dyes acid chlorination/phosgenation reagent in metallurgy to separate ores formerly as war gas... 

Chlorophenoxyalkylcarboxylic acids, salts, and esters (XIX, Fig. 6) are widely used herbicides for control of broadleaf weeds in cereal crops, sugarcane, lawns, woody plants, etc. TLC methods make use of the chlorine content of these herbicides for both detection and separation. 

While chlorinated derivatives are potent herbicides, the structurally related alkyl-substituted phenoxyalkylcarboxylic acids have no pesticidal effect. These compounds are mentioned here because their chromatographic behavior is similar to that of these herbicides. Their separation was studied on reversed-phase TLC (RPTLC) plates having different lengths of carbon chains chemically bonded to silica layers using different mobile phases. This work could provide a possible means for chromatographic studies on their chlorinated derivatives (88) (Table 7). 

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