2,4-Dichlorophenol , detection

Uniformly labeled 2,4-dichlorophenol- C (purchased from New England Nuclear Corp, Boston, Mass.) was used in the tracer preparation. This provided a label at all carbon positions in the dibenzo-dioxin structure. 2,7-Dichlorodibenzo-p-dioxin- C after initial cleanup by fractional sublimation, contained approximately 5% of an impurity, detected by thin layer chromatography (TLC) which gave mass peaks at 288, 290, 292, and 294 in the mass spectrometer, consistent with a trichloro-hydroxydiphenyl oxide. This is probably the initial condensation product of the Ullman reaction and is most likely 2-(2,4-dichlorophenoxy)-4-chlorophenol. It was removed easily by extractions with aqueous... 

Chlorinated dibenzo ip-dioxins are contaminants of phenol-based pesticides and may enter the environment where they are subject to the action of sunlight. Rate measurements showed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is more rapidly photolyzed in methanol than octachlorodi-benzo-p-dioxin. Initially TCDD yields 2,3,7-trichlorodiben-zo-p-dioxin, and subsequent reductive dechlorination is accompanied by ring fission. Pure dibenzo-p-dioxin gave polymeric material and some 2,2 -dihydroxybiphenyl on irradiation. Riboflavin-sensitized photolysis of the potential precursors of dioxins, 2,4-dichlorophenol and 2,4,5-trichloro-phenol, in water gave no detectable dioxins. The products identified were chlorinated phenoxyphenols and dihydroxy-biphenyls. In contrast, aqueous alkaline solutions of purified pentachlorophenol gave traces of octachlorodibenzo-p-dioxin on irradiation. 

The reaction products from 2,4-dichlorophenol were tetrachloro-phenoxyphenols and tetrachlorodihydroxybiphenyls (Figure 5), as determined from their mass spectra and those of their methyl ethers. 4,6-Dichloro-2-(2, 4 -dichlorophenoxy)phenol (V) was the major phenoxy-phenol the mass spectral fragmentation pattern of o-hydroxyphenol ethers is quite characteristic since a hydrogen transfer occurs during the fragmentation (Figure 6). A trace of a trichlorophenoxyphenol also was detected and was formed presumably by the unsensitized reductive loss of chlorine, discussed previously. 

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. 

Lee [42] determined pentachlorophenol and 19 other chlorinated phenols in sediments. Acidified sediment samples were Soxhlet extracted (acetone-hexane), back extracted into potassium bicarbonate, acetylated with acetic anhydride and re-extracted into petroleum ether for gas chromatographic analysis using an electron capture or a mass spectrometric detector. Procedures were validated with spiked sediment samples at 100,10 and lng chlorophenols per g. Recoveries of monochlorophenols and polychlorophenols (including dichlorophenols) were 65-85% and 80-95%, respectively. However, chloromethyl phenols were less than 50% recovered and results for phenol itself were very variable. The estimated lower detection limit was about 0.2ng per g. 

Chinchilla rabbits gavaged once with 500 mg/kg/day 1,4-dichlorobenzene in olive oil excreted 35% of the administered dose in the urine as 2,5-dichlorophenol. Another 6% of the administered dose was excreted in the urine as 2,5-dichloroquinol. At 6 days after dosing, urinary excretion of 1,4-dichlorobenzene metabolites was still in progress however, fecal excretion could not be detected during the 6-day monitoring period (Azouz et al. 1955). 

Several chlorophenols, including 2,5-dichlorophenol, have been identified in laboratory animals exposed to lindane. This indicates that the presence of 2,5-dichlorophenol is fairly specific, but not completely specific, for 1,4-dichlorobenzene exposure. Information on the analytical methods commonly used to detect and quantify 1,4-dichlorobenzene in biological samples is presented in Section 6.1. There are currently no data available to assess a potential correlation between the values obtained with these measurements and the toxic effects observed in humans or laboratory animal species. 

Dichlorophenol may be released to the environment in effluents from its manufacture and use as a chemical intermediate and from chlorination processes involving water treatment and wood-pulp bleaching. Releases can also occur from various incineration processes, from metabolism of various pesticides in soil or in the use of 2,4-D, in which it is an impurity. It has been detected at low levels in drinking-water, groundwater and ambient water samples (United States National Library of Medicine, 1997). 

Compound recovery data for duplicate runs differed by 2-15, depending on the compound. Half-normal probability plot analysis of the new data for the anomalous compounds indicated none of the distortion encountered earlier. Results for acetone and tetrachloroethylene now indicated only random variation with no significant outliers. Results for 2,4-dichlorophenol and 2,5-dichlorophenol indicated a significant pH effect. A significant interaction effect (AB) was detected between variables pH and primary column type for the dichlorophenols and also for methyl isobutyl ketone. This interaction effect indicates that at approximately low pH (pH 2), compound recoveries for dichlorophenols will be greater when a C18 phase is used as the primary column. The half-normal plot for 2,5-dichlorophenol is shown in Figure 10. In examining data for all the compounds from the 23 replicate factorials, this interaction consistently appears for phenolic compounds. 

The only other effect possibly attributed solely to humic acid involved 2,4-dichlorophenol, the most broadly distributed compound tested in this study. In columns 108 and 109, the humic acid apparently decreased the ease of elution of the chlorophenols because lower overall recoveries were obtained from column 109, which included the humate, than from column 108, which was humate-free. Also, recovery was detected in F6 of column 109 but not in F6 of column 108. This result suggests that humate enhanced binding of the phenol to the column. The reproducibility of 2,4-dichlorophenol recovery among the various parfait fractions was poor, as illustrated by the results from replicate columns 117, 118, and 120. Because of the variability, the differences in... 

Three compounds recovered from parfait columns were also previously tested for breakthrough from 5-mL Teflon beds (6). The capacity factors for these compounds and their recoveries from the Teflon bed of a parfait column showed a rough correlation. Phenanthrene, which was tested in the parfait column only in the presence of humate, was recovered essentially quantitatively from the 5-mL Teflon column and had a capacity factor of 368. About 15 of the caffeine applied to a parfait column in the absence of humate could be recovered from Teflon, and caffeine showed a capacity factor of 22. Only about 2 of the 2,4-dichlorophenol applied to parfait columns could be recovered on Teflon its capacity factor was 5.6. It may therefore be anticipated that compounds following the inverse correlation of solubility with capacity factor and having a capacity factor greater than about 20 should be detectably absorbed to the Teflon bed of a parfait column. Simply increasing the volume of the Teflon bed may also increase the absolute recovery of adsorbable solutes that have modest values of kFor this reason, a 150-mL bed of Teflon per 8 L of water may not be the ideal bed size a larger bed may be better. 

It is often possible to quantify the presence of natural molecules in biological samples without actually isolating the molecules. Two such analyses will be completed in this experiment (1) serum cholesterol will be measured by coupling its enzyme-catalyzed oxidation to the peroxidase-catalyzed formation of a chromogen, and (2) the presence of vitamin C in dietary materials will be detected and quantified by redox titration with 2,6-dichlorophenol-indophenol. 

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... 

Fig.4.71. Separation of some chlorophenols by cerium(IV) oxidation and fluorimetric detection. Column Corasil-C, 0.61 m X 4.83 mm I.D. Gradient elution from water to 36% acetonitrile-64% water. Peaks 1 = phenol (18.4 ppb) 2 = o-chlorophenol (22.S ppb) 3 = p-chlorophenol (20.2 ppb) 4 2,4-dichlorophenol (52.2 ppb) 5 = 2,4,6-trichlorophenol (42.6 ppb) S = solvent.

The method used by Yorkshire Water Authority [42] for determining phenols in potable waters has a criterion of detection of 3-70pg depending on the phenol. It is capable of determining phenols and cresols, xylenols, dihydric phenols, monochlorophenols, dichlorophenols and trichlorophenols. The phenols are extracted from the water sample with ethyl acetate using a liquid-liquid extractor. After drying, the extract is concentrated to a small volume then treated with... 

GC-MS and HPLC analyses of electrolyzed solutions allowed the detection of aromatic intermediates such as p-benzoquinone and nitrobenzene for aniline, 4-chlorocatechol for 4-chlorophenol, 4-chlorophenol, 4-chlorocatechol, hydroquinone, and p-benzoquinone for 4-CPA, 4-chloro-o-cresol, mehylhy-droquinone, and methyl-p-benzoquinone for MCPA, 2,4-dichlorophenol, 4,6-dichlororesorcinol, chlorohydroquinone, and chloro-p-benzoquinone for 2,4-D, and 2,4,5-trichloro-phenol, 2,5-dichlorohydroquinone, 4,6-dichlororesorcinol, and 2,5-dihydroxy-p-benzoquinone for 2,4,5-T. In general, these by-products persisted in solution while the initial pollutant was degraded. 

The fate of the ring structure in soils has also been studied. Detection of 2,4-dichlorophenol, 4-chlorocatechol, and chloromuconic acid (9) from either soil or pure culture studies suggests a sequence of reactions involving ring hydroxylation and cleavage and further metabolism of the open chain structure to C02. 

In addition to hydroxy-PCDEs, nitro- and aminoderivatives of PCDEs could be possible sources of PCDEs in the environment. Nitrofen is prepared by base-catalyzed condensation of 2,4-dichlorophenol (2,4-DCP) with l-chloro-4-nitrobenzene [30]. PCDEs have not been detected in 2,4-DCP and 2,4,5-TCP [37] but, in theory, just as the occurrence of PCDE by-products in chlorophe-nols is most likely due to the condensation of chlorophenols, the condensation of 2,4-dichlorophenol during the manufacture of nitrofen might lead to the formation of PCDEs. Aminofen is produced from nitrofen by catalytic reduction [4],... 

Although it is generally believed that under anaerobic conditions dechlorination, either reductive or hydrolytic, precedes ring fission, this pathway has been clearly documented only for the methanogenic studies. The physical proof and transient appearance of each dechlorinated metabolite (e.g., 2,3,6-trichlorophenol — 2,3-dichlorophenol — 3-monochlorophenol), which is seen in methanogenic cultures, has not been observed for the sulfidogenic or denitrifying cultures. It is still unclear whether this indicates that there is indeed a different mechanistic pathway or whether the rates of metabolite transformation are so rapid that they preclude their detection. 

A comparison study of Cig-bonded silica cartridges and polystyrene-divinylbenzene copolymer membrane absorption disks showed that the latter were the more effective for SPE of phenols at the 0.5 ppb concentration levels (70-98% recoveries), whereas the Cis cartridges were preferable for higher concentration levels (10 ppb) because smaller sample and solvent volumes were required and analysis time was therefore shorter. End analysis was by LC-ELD, with a phosphate buffer-acetonitrile-methanol mixture as mobile phase and coulometric detection at +750 mV. A study was carried on the preconcentration step of phenol, < -, m-, p-methylphenol, < -, m-, p-chlorophenol, 2,5-, 2,6-dichlorophenol, catechol (42), resorcinol (20) etc., at 0.5 and 5 figL concentrations. SPE utilizing a divinylbenzene-hydrophilic methacrylate copolymer gel showed recoveries better than... 

The herbicide compounds 2,4-D and 2,4,5-T, found to be 280 and 610 ppm in the feedstock, respectively, were also destroyed during the process to levels less than detectable, which were 0.01 ppm. 2,4,5/2,4,6-trichlorophenol and 2,4-dichlorophenol, found at 55 ppm and 10 ppm in the feedstock, were destroyed to levels less than detectable, which were 1 ppm. Chlorinated organic pesticides and PCBs were not detected in the feedstock hence, destruction could not be evaluated. Earlier AER tests conducted by Huber on the destruction of PCBs and carbon tetrachloride in soil for Toxic Substance Control Act (TOSCA) and Resource Conservation and Recovery Act (RCRA) permits have shown the process to be highly effective. 

The bromophos content of treated products rapidly decreases, after 10 days being less than 1 ppm, and after 20 days it can no longer be detected. Its most important metabolites injilant tissues are 4-bromo-2,5-dichlorophenol, bromoxon (41), formed by the exchange of thion-sulfur for oxygen, and mono-demethyl-bromophos (42), formed by partial demethylation (Stiasni et al., 1969). 

Study on the occurrence and levels of pesticides residues in the river Danube has established the presence of organochlorine pesticides (HCH isomers, HCB and DDT), atrazine and desethylatrazine. Simazine and chlorinated phenols (2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) were also detected (Bratanova Z. et al., 1998). Relatively high levels of DDT and metabolites in the water samples after incidents with pesticide stocks are reported (Kambourova et al., 2005). Atrazine and lindane also were found (Bratanova Z. et al., 2000). 

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