Chlorinated compounds, analysis

We conclude the current vignette with a brief discussion of difluoroacetylene, FC=F, and compare it with the parent and monofluorinated species. The C=C and C-F bond lengths seem to be almost identical for these compounds. From the above chlorinated compound analysis and earlier experience with multiply fluorinated compounds [77], we know enough not to conclude that the reaction. 

Chlorinated compounds" Analysis for CIO and CIO2 in disinfected water... 

An analysis of six municipal solid waste samples from Hamburg, Germany, revealed levels of trichloroethylene ranging from undetectable to 0.59 mg/kg (Deipser and Stegmaim 1994). In a study analyzing automobile exhaust for chlorinated compounds, trichloroethylene was not detected (Hasanen et al. 1979). 

Chemical analysis revealed that commercial food grade copper chlorophyllin is not a single, pure compound, but is a complex mixture of structurally distinct porphyrins, chlorin, and non-chlorin compounds with variable numbers of mono-, di-, and tri- carboxylic acid that may be present as either sodium or potassium salts. Although the composition of different chlorophyllin mixtures may vary, two compounds are commonly found in commercial chlorophyllin mixtures trisodium Cu (II) chlorin Cg and disodium Cu (II) chlorin which differ in the number of... 

Methoxychlor [1,1,l-trichloro-2,2-bis(p-methoxyphenyl)-ethane], benzene hexachloride (BHC), chlordan, and toxaphene are chlorinated compounds of recognized importance in the insecticide field. Other chlorinated compounds now undergoing-field testing experiments will, no doubt, soon be added to the list. The need for specific analytical methods is familiar to those concerned with the analysis of formulations containing one or more of the above insecticides. 

The relative ratio of regioisomers of PCDD/F and other chlorinated compounds formed in incinerators is called the incineration pattern. The pattern can be derived from statistical analysis of a large number of measurements of the same plants, and can be used for elucidation of thermal formation mechanisms in plants. In principle regioisomers can be formed either by stereospecific chlorination or dechlorination processes. The pattern has also been used as a part for explaining of the formation mechanism of PCDD/F and other chlorinated compounds formed in incinerations (see Figure 8.4). 

Automated extraction and analysis of chlorinated compounds by large 188... 

AUTOMATED EXTRACTION AND ANALYSIS OE CHLORINATED COMPOUNDS BY LARGE VOLUME ON-COLUMN INJECTION GC/MSD... 

Kadry et al. (1995) evaluated the UF for LOAEL to NOAEL extrapolation by comparing subchronic (23) and chronic (23) LOAEL/NOAEL ratios for six chlorinated compounds. All of the ratios were 10 or less for subchronic exposure, 91.3% of the ratios were sixfold or less and for chronic exposure, 87% of the ratios were 5 of less. The authors concluded that automatic safety factors of 10-fold are not scientifically supportable and are overly conservative for the chlorinated compounds included in their analysis. 

Stein VB, Narang RS. 1984. Chlorinated compounds and phenols in tissue, fat, and blood from rats fed industrial waste site soil extract methods and analysis. J Assoc Off Anal Chem 67 111-116. 

Chlorine Residual Extraction. A 400-mL solution of distilled water containing 70 ppm of sodium bicarbonate, 120 ppm of calcium sulfate, and 47 ppm of calcium chloride was extracted under typical operational conditions. Similarly, a solution containing all of these materials plus a 2-ppm chlorine residual (prepared with NaOCl) was extracted. Analysis of the U-tube traps, feedstock, and raffinate solutions in each case (blank and chlorine residual samples) showed that no new chlorinated compounds were formed by the presence of a chlorine residual. 

Gribble GW (1998) Chlorinated Compounds in the Biosphere, Natural Production. In Meyers RA (ed) Encyclopedia of Environmental Analysis and Remediation. Wiley, New York, p 972... 

Holmstrand H, Gadomski D, Mandalakis M, Tysklind M, Irvine R, Andersson P, Gustafsson O (2006) Origin of PCDDs in Ball Clay Assessed with Compound-Specific Chlorine Isotope Analysis and Radiocarbon Dating. Environ Sci Technol 40 3730... 

ELUmo measures the ability of a molecule to accept electrons. Compounds with low Elumo tend to accept electrons easily. Thus, the coefficient of ELUMO is negative. Theoretically a compound with more negative AHf or lower AHf is more stable (Fried et al., 1977) therefore, it is reasonable that the coefficient of AHf in Equation (13.50) is positive, as shown in Table 13.13. Thus, the higher the AHf value is, the more unstable or reactive the chlorinated compounds will be. As a result, the log k values are greater. LFER analysis on dechlorination by Fe° of chlorinated aliphatic compounds, ELUMO, and AHf have been confirmed to be more significant molecular descriptors than other... 

In this manner, a nearly universal and very nonselective detector is created that is a compromise between widespread response and high selectivity. For example, the photoionization detector (PID) can detect part-per-billion levels of benzene but cannot detect methane. Conversely, the flame ionization detector (FID) can detect part-per-billion levels of methane but does not detect chlorinated compounds like CCl very effectively. By combining the filament and electrochemical sensor, all of these chemicals can be detected but only at part-per-million levels and above. Because most chemical vapors have toxic exposure limits above 1 ppm (a few such as hydrazines have limits below 1 ppm), this sensitivity is adequate for the initial applications. Several cases of electrochemical sensors being used at the sub-part-per-million level have been reported (3, 16). The filament and electrochemical sensor form the basic gas sensor required for detecting a wide variety of chemicals in air, but with little or no selectivity. The next step is to use an array of such sensors in a variety of ways (modes) to obtain the information required to perform the qualitative analysis of an unknown airborne chemical. 

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 ... 

Chlorinated compounds such as PCBs, haloethers, chloronaphthalenes, etc., which may be present in several orders of magnitude higher than the analytes of interest, can interfere in the analysis. These interfering substances may be removed from the solvent extracts as follows. 

Many chlorinated compounds and organic acids may interfere in GC-ECD analysis. Some basic and neutral interference can be removed by acid-base partitioning sample cleanup. 

Add 0.008% of sodium thiosulfate (Na2S203) to all samples collected for organic compound analysis with the exception of SW-846 Methods 8081, 8082, and 8141, if residual chlorine is present. 

Any compound that yields ions listed in Table 5 and also elutes within the retention time window of the corresponding homologue is a potential interference. PCDDs/PCDFs are often associated with other chlorinated compounds such as polychlorinated biphenyls (PCBs) and polychlorinated diphenyl ethers (PCDPEs). These compounds may be found at concentrations several orders of magnitude higher than that of the analytes of interest and may otherwise interfere with the analysis of PCDDs/PCDFs. Therefore the retention time of the target analytes must be verified using reference standards and compared to retention time... 

Unlike the case for other chlorinated compounds such as PCBs, double charged ions (at m/z values < MG/2 and with only 1 u between the chlorine isotope peaks) have not been mentioned for toxaphene components. The analysis of the GC/EI-MS fragmentation patterns allows a partial structure elucidation and the confirmation of the presence of a bornane skeleton. This knowledge facilitates a further structure elucidation by H-NMR spectroscopy [111]. 

In another example, copper (Cu) reacts with chlorine (Cl) under different sets of conditions to form two different compounds. Table 3-6 provides an analysis of their composition. Note that the two copper compounds must be different because they have different percents by mass. Compound I contains 64.20% copper compound II contains 47.27% copper. Compound I contains 35.80% chlorine compound II contains 52.73% chlorine. 

Chlorine (Cl) and oxygen form four different binary compounds. Analysis gives the following results ... 

By calculation the numbers yield a somewhat smaller quantity of carbon and hydrogen than was obtained by analysis. The reason undoubtedly is that in preparing the chlorine compound, perhaps Yq q-q- of the oil of bit. aim. escapes with the chlorine. In no case is the difference of such importance, that the conclusion to which we arrive respecting the composition of this body, can be considered false. 

GC on a fused silica capillary column with an MS detector should be used whenever possible for the analysis of organic compounds at trace level in complex mixtures. In fact, it allows the extremely high resolution of GC to be combined with the very high sensitivity and identification power of MS, which makes it possible to determine an analyte at low pg mC levels in the final organic extract. However, GC-ECD is very common for PCB determination since it is both the most sensitive and the less expensive technique for chlorinated compounds (5). PCBs can be separated on a 30-50 m fused silica capillary column with 5% phenyl -95% methylpolysiloxane chemically bonded stationary phase (1). On-column injection is very often used, while several oven temperature programmes have been applied for PCB determinations. The initial temperature is generally 10-15°C lower than the boiling point of the solvent and the final one does not exceed 290-300°C. 

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