Chlorinated acid herbicides determining

This method complements the U.S. Environmental Protection Agency s gas chromatographic (GC) SW-846 Method 8151 for the determination of chlorinated acid herbicides. Method 8151 prescribes the use of hydrolysis to ensure that these compounds arc in the acid form, reaction of the acids with diazomethane to produce methyl esters, and GC or GC/MS analysis. This HPLC method eliminates the need for most sample preparation steps and allows direct analysis of sample extracts. 

In many contributions reporting on acidic pesticides in environmental samples ESI applied as ion spray was predominantly performed to analyse these pollutants. APCl, however, was not as effective as ESI as studies with standard solutions of the pesticide mixtures made obvious [325] when phenoxy acid compounds were determined using both types of interface. MSn quantitative results were used for confirmation. Mass detection after CZE-MS interfaced by ESI was successfully apphed to analyse drinking water spiked with chlorinated acid herbicides. Selected-ion elec-... 

X. Song and W.L. Budde, Determination of chlorinated acid herbicides and related compounds in water by capillary electrophoresis-electrospray negative ion mass spectrometry, J. Chromatogr. A, 829, 327-340, 1998. 

DETERMINATION OF NONVOLATILE COMPOUNDS AND CHLORINATED ACID HERBICIDES... 

Renberg [35] used an ion-exchange technique for the determination of chlorophenols and phenoxy acetic acid herbicides in soil. In this method the soil extracts are mixed with Sephadex QAE A-25 anion exchanger and the adsorbed materials are then eluted with a suitable solvent. The chlorinated phenols are converted into their methyl ethers and the chlorinated phenoxy acids into their methyl or 2-chloroethyl esters for gas chromatography. 

Chlorinated [407,408] and 2,4-dinitrophenoxy acid herbicides [409] have been determined. liquid chromatography particle beam mass spectrometry has been used as an analytical finish [408]. Crescenzi et al. [410] evaluated the feasibility of selectively and rapidly extracting herbicide residues in soils by hot water and collecting analytes with a Carbograph 4 solid-phase extraction cartridge set on-line with the extraction cell. Phenoxy acid herbicides and those non-acidic and acidic herbicides that are often used in combination with phenoxy acids were selected for this study. Five soil samples were... 

Takino, M., Daishima, S., and Nakahara, T., Automated online in-tube solid-phase microextraction followed hy liquid chromatography/electrospray ionization-mass spectrometry for the determination of chlorinated phenoxy acid herbicides in environmental water. Analyst, 126, 602-608,... 

Di Corcia and Marchetti [160] determined chlorinated phenoxy acid and ester type herbicides in amounts down to lmg kg-1 or lower in soil by liquid chromatography combined with particle beam mass spectrometry and ultraviolet absorption spectrometry. 

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 ... 

Gas chromatography has been applied to the determination of a wide range of organic compounds in trade effluents including the following types of compounds which are reviewed in Table 15.15 aromatic hydrocarbons, carboxylic acids aldehydes, non ionic surfactants (alkyl ethoxylated type) phenols monosaccharides chlorinated aliphatics and haloforms polychlorobiphenyls chlorlignosulphonates aliphatic and aromatic amines benzidine chloroanilines chloronitroanilines nitrocompounds nitrosamines dimethylformamide diethanolamine nitriloacetic acid pyridine pyridazinones substituted pyrrolidones alkyl hydantoins alkyl sulphides dialkyl suphides dithiocaibamate insecticides triazine herbicides and miscellaneous organic compounds. 

Solvent type Acetone hexane (1 1 (vol/vol)) acetone DCM (1 1 (vol/vol)) DCM only toluene methanol (10 l(vol/vol)) alternatively, a solvent system of your own choice As Soxhlet As Soxhlet Requires optimization CO2 (plus organic modifier). Tetra- chloroethene used as the collection solvent for TPHs for determination by FTIR otherwise, DCM Typically, acetone hexane (1 1 (vol/vol)). The solvent(s) is/are required to be able to absorb microwave energy Acetone hexane (1 1 (vol/vol)) or acetone DCM (1 1 (vol/vol)) for OCPs, semi-volatile organics, PCBs or OPPs acetone DCM phosphoric acid (250 125 15(vol/vol)) for chlorinated herbicides... 

Kim, I.S., F.I. Sasins, R.D. Stephens, J. Wang, and M.A. Brown. 1991. Determination of chlorinated phenoxy acid and ester herbicides in soil and water by liquid chromatography particle beam mass spectrometry and ultraviolet spectrophotometry. Anal. Chem. 63 819-823. 

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