Chlorophenols, determination

The quantum yield of conversion of 4-chlorophenol was not measured with high accuracy ( 0.4 0.1 ). At low conversion rate (<0.1), the relative error on the conversion of 4-chlorophenol determined by HPLC measurement is about 25%. Moreover, the optical density at 254 nm increeised much with the progress of the reaction ( about a factor of 5 for 15% of transformation ). At conversion rates higher than 0.1, secondary reactions are not negligible trtien the solution was Irradiated at 296 nm. Nevertheless, the initial quantum yield of formation of Cl ( 0.25 0.05 ) appeared to be significantly lower than the quantum yield of conversion of 4-chlorophenol (37). 

Chlorophenols, determination of 102-104, 285, 350 Chlorophylls, determination of 104-106,203-205, 248-260 Chromatographic detectors, atomic absorption 32-33 fluorescence 29-31 infrared 31, 32 inductively coupled plasma atomic emission 33-35 Raman 31, 32 visible 29 Chromate, determination of 60-65 Chromium, determination of 166, 234, 235,477-481... 

Chlorination of Phenols. Industrially, the phenols are chlorinated without solvent. Chlorine reacts rapidly with phenol and with the chlorophenols, which makes it difficult to determine the relative reaction rates because of the superchi orin ation that sometimes results from an unsatisfactory chlorine dispersion. Studies have yielded the relative reaction rates iadicated ia Figure 1. 

Therefore, hplc methods seem more effective. By usiag a combiaed uv and electrochemical detection technique (52), the gem-chlotinated cyclohexadienones, the chlorophenols, and the phenoxyphenols present ia the chlorination mixtures can be determined with great accuracy. 

For selective estimation of phenols pollution of environment such chromatographic methods as gas chromatography with flame-ionization detector (ISO method 8165) and high performance liquid chromatography with UV-detector (EPA method 625) is recommended. For determination of phenol, cresols, chlorophenols in environmental samples application of HPLC with amperometric detector is perspective. Phenols and chlorophenols can be easy oxidized and determined with high sensitivity on carbon-glass electrode. 

Determination of C -C cai bonyl compounds, phthalic acid alkyl esters, mutagen MX and its geometric isomer E-MX, chlorophenols, organochlorine pesticides (OCPs) - a-, P-, J-, 5-HCH, DDE, DDD, DDT, total isomeric-specific content of polychlorinated byphenyls (PCBs) (tri-, tetra-, penta-, hexa-, hepta-, octachloroisomers) in SCAN and SIM mode was canned out. MDE of procedure for OCPs makes up 0.01-0.1 and PCBs - 0.17-0.38 ng/1 at enrichment factor K = (1.50-4.00)T0. ... 

Eire protection - Eire extinguishing media - Elalogenated hydrocarbons. Code of practice for safe handling and transfer procedures. Supersedes BS 6535 Section 2.2 1989 Water quality - Gas chromatographic determination of some selected chlorophenols m water. Also BS 6068-2.65 1999... 

The objectives of the soil persistence experiments were (1) to learn the effect of soil type and concentration on the TCDD degradation rate, (2) to isolate and characterize degradation products from DCDD and TCDD, and (3) to determine whether chlorodioxins could be formed from chlorophenol condensation in the soil environment. This last study was essential since quality control at the manufacturing level could reduce or eliminate the formed dioxin impurity. But the biosynthesis of chlorodioxins by chlorophenol condensation in the soil environment could not be controlled and would have connotations for all chlorophenol-de-rived pesticides if formation did occur. The same question needed to be answered for photochemical condensation reactions leading to chloro-... 

The most convenient and successful synthetic preparation of octa-chlorodibenzo-p-dioxin has been described by Kulka (13). The procedure involves chlorination of pentachlorophenol in refluxing trichlorobenzene to give octachlorodibenzo-p-dioxin in 80% yield. Kulka has explained the reaction as coupling between two pentachlorophenoxy radicals. Large amounts (5—15%) of heptachlorodibenzo-p-dioxin were observed in the unpurified product. Since the pentachlorophenol used in this study contained 0.07% tetrachlorophenol, we feel that tetrachloro-phenol may be produced in situ (Reaction 4). Such a scheme would be analogous to the formation of 2,4-dichlorophenol and 3-chlorophenol produced from 2,4,4 -trichloro-2 -hydroxydiphenyl ether (Reaction 2). The solubility of octachlorodibenzo-p-dioxin was determined in various solvents data are presented in Table II. 

An HPLC-CL determination of environmentally important chlorophenols was reported by using 10-methyl-9-acridinium carboxylate as a CL label. A two-step derivatization was used to produce the CL derivatives (Fig. 10). Following the separation under reversed-phase conditions, the CL reaction was performed by the base-catalyzed postcolumn oxidation. The quantum efficiency was dependent on the species of analytes. The detection limit of chlorophenols (S/N = 3) ranged from 300 amol to 1.25 fmol per injection (Fig. 11) [52],... 

Butler, E.C.V. and G.D. Pont. 1992. Liquid chromatography-electrochemistry procedure for the determination of chlorophenolic compounds in pulp mill effluents and receiving waters. Jour. Chromatogr. 609 113-123. 

Although the use of organochlorinated substances has been abolished in most of the developed countries, their extensive use during the past decades and their persistence in the environment determine their actual widespread distribution. Moreover, some substances are not used or commercialized but are still important synthetic intermediates for the preparation of other substances. Thus, chlorophenols are important intermediates in the production of pesticides or other chemicals. Other substances such as PCDEs or PCDDs are... 

Wei M-C, Jen J-F. Determination of chlorophenols in soil samples by microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-electro-capture detection. J. Chromatogr. A 2003 1012 111-118. 

Suppliers of visible spectrophotometers are reviewed in Table 1.1. Spectroscopic methods are applicable to the determination of phenols, chlorophenols, amines, mixtures of organics, boron, halogens, total nitrogen and total phosphorus in soils, cationic surfactants, carbohydrates, total nitrogen, phosphorus and sulphur in non-saline sediments, boron, total organic carbon, total sulphur and arsenic in saline sediments, cationic surfactants, adenosine triphosphate and total organic carbon in sludges. 

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. 

The results obtained in determining various chlorophenols in soil are shown in Table 5.2. 

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. 

Xie [39] determined trace amounts of chlorophenols and chloroguaiacols in marine sediments collected off the Swedish coast. The compounds were desorbed from sediment surfaces by a mixture of acetic anhydride and hexane, after buffering with O.lmol L 1 sodium carbonate. The optimal pH was achieved by a 1 4 ratio of buffer to acetic anhydride. The acetylated extracts were analysed by glass capillary gas chromatography with electron capture detection. The recoveries, at the pg kg-1 level, ranged from 85-100% with standard deviations of 4-11%. 

It is difficult to compare recoveries obtained by different laboratories because their extraction conditions (pH, phase ratio, number and time-length of extractions, salinity) are generally different. Sample volumes can be very high, up to 200 1 [433], and 50 1 of surface water [434] or 201 of sea water allow the extraction of 5 ng/1 of alkanes. When using a specific detection method, the sample volume can be lower 2 ng/1 of PAH was determined from 11 of river water using liquid chromatography and fluorescence detection [435]. Chlorophenols below the 10 ng/1 level were determined from 100 ml of sea water with electron capture detection (ECD) GC [436]. 

Geibler A, Scholer HF. 1994. Gas chromatographic determination of phenol, methylphenols, chlorophenols, nitrophenols, and nitroquinones in water. Water Research 28 2047-2053. 

Chemical/Physical. Chemical oxidation of mono-, di-, and trichlorophenols using Fenton s reagent were investigated by Barbeni et al. (1987). To a 70-mL aqueous solution containing 4-chlorophenol thermostated at 25.0 °C was added ferrous sulfate and hydrogen peroxide solution (i.e., hydroxyl radicals). Concentrations of 4-chlorophenol were periodically determined with... 

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