2.4- Dichlorophenoxyacetic acid determination

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.

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-... 

Furthermore, the use of Ralstonia eutropha JMP134-containing sensors for the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been described [118,121]. This sensor was sensitive to 2,4-D and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) with a detection Emit of 40 mg 1 with a response time of 15 s. Moreover, catechol, benzoic acid, and sahcylaldehyde caused higher signals, but no or very little signal was obtained for phenol, biphenyl, and the usual substrates such as glucose, fructose, ethanol, and acetate. 

For instance, a 2,4-dichlorophenoxyacetic acid systemic herbicide has been determined by adopting this procedure. 2,4-Dichlorophenol and 2,5-dihydroxyphe-nylacetic acid (also known as homogentisic acid) were used as electroactive competitors and DPV for signal transduction [6]. Likewise, 2-chloro-4-hydroxy-phenoxyacetic acid was applied as the electroactive competitor for detection of the... 

M. Dequaire, C. Degrand and B. Limoges, An immunomagnetic electrochemical sensor based on a perfluorosulfonate-coated screen-printed electrode for the determination of 2,4-dichlorophenoxyacetic acid, Anal. Chem., 71 (1999) 2571-2577. 

Cuong, N.V., T.T. Bachmann, and R.D. Schmid. 1999. Development of a dipstick immunoassay for quantitative determination of 2,4-dichlorophenoxyacetic acid in water, fruit and urine samples. Fresenius J. Anal. Chem. 364 584-589. 

Other factors influence the magnitude of the effect of exposure misclassification on estimates of association between exposures and disease. The effect depends not only on the extent of exposure misclassification, but also on the prevalence of exposure in the population studied. Since pesticide exposure prevalence may differ in different populations and is certainly different in general population stndies when compared to studies in farming communities, the performance of exposnre assessment techniques will vary according to the study context. The specificity determines the bias in risk-ratio situations with a low exposure prevalence. Thus, a poor sensitivity, for instance, the one reported by Arbuckle et al. (2002) for 2,4-dichlorophenoxyacetic acid (2,4-D), may not be problematic in a general population or case-control study, as long as the specificity is sufficiently high. 

The second case taken from the author s own work uses LLE to initially clean up an aqueous sample taken from the environment that might contain, in addition to the analyte of interest, other organic compounds that may interfere in the determinative step (9). The analytes of interest are the class of chlorophenoxy herbicides (CPFIs) and includes 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4,5-trichlorophenoxypropionic acid (Silvex). CPFIs are... 

Gas Chromatographic Determination of 2,4-Dichlorophenoxyacetic Acid (2,4-D) in Urine by Mass Fragmento-graphy with a Deuterated Internal Standard... 

Yongliang Liu, He Yonghuan, Jin Yulong, Huang Yanyan, Liu Guoquan, and Zhao Rui. Preparation of monodispersed macroporous core-shell molecularly imprinted particles and their application in the determination of 2,4-dichlorophenoxyacetic acid. J. Chromatogr. A. 1323 (2014) 11-17. 

PCDDs have been detected in trichlorophenol (TCP), tetrachlorophenol (TeCP), and pentachlorophenol (PCP) and in chlorophenol derivatives such as 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Since combustion of organic materials and seepage from chemical dumps also apparently generate detectable residues in the environment, PCDDs are now suspected to be ubiquitous contaminants in both aquatic and terrestrial ecosystems. However, it is not possible to estimate accurately the amounts of PCDDs discharged to the environment or to measure residues except in cases of extreme ambient contamination, and thus the overall threat posed by PCDDs has not been determined at the present time. 

Rates of hydrolysis may be influenced by the presence of dissolved organic carbon or sediment and the effect is determined by the structure of the compound and by the kinetics of its association with these components. For example, whereas the neutral hydrolysis of chlorpyrifos was unaffected by sorption to sediments, the rate of alkaline hydrolysis was considerably slower (Macalady and Wolf 1985) humic acid also reduced the rate of alkaline hydrolysis of 1-octyl 2,4-dichlorophenoxyacetate (Perdue and Wolfe 1982). Conversely, sediment sorption had no effect on the neutral hydrolysis of 4-chlorostilbene oxide although the rate below pH 5 where add hydrolysis dominates was reduced (Metwally and Wolfe 1990). 

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