Acidic herbicides

Phenoxyalkanoics. The phenoxyalkanoic herbicide grouping is composed of two subgroups, the phenoxyacetic acids and the phenoxypropionic acids. The phenoxyacetic acid herbicides include some of the first commercially successhil herbicides, eg, 2,4-D. They continue to be widely used for foUar control of broadleaf weeds. The more heavily functionalized phenoxypropionic acid herbicides are relatively new herbicides compared to the phenoxyacetic acids and are used primarily for selective control of grassy weeds in broadleaf crops (2,296,297). 

The major use of alkan olamines in agricultural products is as a neutralizer for acidic herbicides. They also contribute increased water solubiUty, reduced volatility, and more uniform solutions. Various ethan olamines are reported in formulations to improve potato tuber size (219) and enhance the resistance to salt of some crops (220). 

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. 

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

With dicamba, a more polar chlorobenzoic acid herbicide, a gradient step is needed to elute all of the compounds in one chromatographic run. Depending on the buffer and selectivity of the detector, the baseline can be severely disturbed. If this happens, a step-gradient elution is recommended (52), and in this way the method can detect all of the compounds at very low levels. 

E. A. Hogendoorn, E. Dijkman, B. Baumann, C. Hidalgo, J. V. Sancho and E. Hernandez, Strategies in using analytical restricted access media columns for the removal of humic acid interferences in the trace analysis of acidic herbicides in water... 

Phenothiazines 44, 59, 299, 411, 413,416 Phenoxyacetic acid herbicides 260 Phenoxyalkanecarboxylic acid esters 210, 211... 

Another case of high nitrosamine concentration in chlorinated phenoxy- and benzoic acid herbicides was resolved by the elimination by the manufacturer of nitrite salts in the formu-... 

Buser H-R, MD Muller (1997) Conversion reactions of various phenoxyaUcanoic acid herbicides in soil 2 elucidation of the enantiomerization process of chiral phenoxy acids from incubation in a DjO/soil system. Environ Sci Technol 31 1960-1967. 

Gintautas PA, SR Daniel, DL Macalady (1992) Phenoxyalkanoic acid herbicides in municipal landfill leachates. Environ Sci Technol 26 517-521. 

Crescenzi et al. developed a multi-residue method for pesticides including propanil in drinking water, river water and groundwater based on SPE and LC/MS detection. The recoveries of the pesticides by this method were >80%. Santos etal. developed an on-line SPE method followed by LC/PAD and LC/MS detection in a simultaneous method for anilides and two degradation products (4-chloro-2-methylphenol and 2,4-dichlorophenol) of acidic herbicides in estuarine water samples. To determine the major degradation product of propanil, 3,4-dichloroaniline, the positive ion mode is needed for atmospheric pressure chemical ionization mass spectrometry (APCI/MS) detection. The LOD of 3,4-dichloroaniline by APCI/MS was 0.1-0.02 ng mL for 50-mL water samples. 

Lord and Pawliszyn" developed a related technique called in-tube SPME in which analytes partition into a polymer coated on the inside of a fused-silica capillary. In automated SPME/HPLC the sample is injected directly into the SPME tube and the analyte is selectively eluted with either the mobile phase or a desorption solution of choice. A mixture of six phenylurea pesticides and eight carbamate pesticides was analyzed using this technique. Lee etal. utilized a novel technique of diazomethane gas-phase methylation post-SPE for the determination of acidic herbicides in water, and Nilsson et al. used SPME post-derivatization to extract benzyl ester herbicides. The successful analysis of volatile analytes indicates a potential for the analysis of fumigant pesticides such as formaldehyde, methyl bromide and phosphine. 

Electrospray ionization (ESI) and APCI are the two popular API techniques that will be discussed here. The applications to the analysis of pesticides that will be discussed include imidazolinone herbicides, phenoxy acid herbicides, and A-methyl carbamate insecticides. Matrix effects with respect to quantitation also will be discussed. Eor the... 

ESI performs well for the more polar compounds such as imidazolinone herbicides, sulfonylurea herbicides, triazine herbicides, phenoxy acid herbicides, and carbamate pesticides (to name a few). ESI also performs well with proteins and peptides. 

Chiron et al. used HPLC/ESI-MS in the negative mode for the determination of acidic herbicides in environmental waters. The acidic herbicides investigated were benazolin, bentazone, 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-... 

Table 7 List of ions monitored for acidic herbicides (HPLC/ESI-MS)...

Sbrana I, Di Sibio A, Lomi A, Scarcelli V (1993) C-mitosis and numerical chromosome aberration analyses in human-lymphocytes - 10 known or suspected spindle poisons. Mutat Res 287 57-70 Senesi N, Loffredo E, Padovano G (1990) Effects of humic acid-herbicide interactions on the growth of Pisum sativum in nutrient solution. Plant Soil 127 41-47... 

Fig. 3 Scientific studies in water. Ph pharmaceuticals Ft phthalates Fu fungicides HA acidic herbicides HCB hexachlorobenzene PCBs polychlorinated biphenyls OCs organochlorine pesticides PPs polar pesticides...

Chiron S, Papilloud S, Haerdi W, Barcelo D (1995) Automated online liquid-solid extraction followed by liquid chromatography-high-flow pneumatically assisted electrospray mass-spectrometry for the determination of acidic herbicides in environmental waters. Anal Chem 67(9) 1637-1643... 

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