Extraction chlorine residual

One of the most widely established processes using SCCO2 is the decaffeination of coffee. Prior to widespread use of this process in the 1980s the preferred extraction solvent was dichloromethane. The potential adverse health effects of chlorinated materials were realized at this time and, although there was no direct evidence of any adverse health effects being caused by any chlorinated residues in decaffeinated coffee there was always the risk, highlighted in some press scare stories. Hence the current processes offer health, environmental and economic advantages. 

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. 

Chlorinated [407,408] and 2,4-dinitrophenoxy acid herbicides [409] have been determined. liquid chromatography particle beam mass spectrometry has been used as an analytical finish [408]. Crescenzi et al. [410] evaluated the feasibility of selectively and rapidly extracting herbicide residues in soils by hot water and collecting analytes with a Carbograph 4 solid-phase extraction cartridge set on-line with the extraction cell. Phenoxy acid herbicides and those non-acidic and acidic herbicides that are often used in combination with phenoxy acids were selected for this study. Five soil samples were... 

That dechlorinations w re accelerated by the ZV-metal particles was demonstrated by replacing the metal particles with silica (acid washed sea sand). For the silica column operated under dechlorinating conditions that had been optimal for ZV metal (400 C, 31.0 MPa), the recovery of organically bound chlorine from the eluate was virtually quantitative. In further trials, acetone-hexane extract of a sandy loam soil (spiked with 600 ppm Aroclor 1254) was fed to the reactor at 0.1 mLymin and dechlorinated efficiently. Chlorinated residues were not detected in the reactor effluent by GC-MS. More importantly, soil co-extractives in the PCB solution did not seem to affect the course or the efficiency of the reaction perceptibly. 

Euxenite (ideal formula (Y, Ca, Ce)(Nb, Xa)206), is treated by reductive chlorination, which is followed by distillation of the chlorides to separate the rare earths, titanium, niobium and tantalum. Solvent extraction can be used to remove tantalum and niobium chlorides and the rare earths from the chlorination residue (Gupta and Krishnamurthy 2005). 

The FDA has pubhshed methods for the deterrnination of residual solvents in spice extracts such as oleoresins and has limited the concentrations of those specific solvents that are permitted. Chlorinated hydrocarbons and benzene have been almost completely removed from use as extracting solvents in the United States their use continues overseas where toxicity regulations are less stringent. The presence of pesticides or herbicides in spices is rigidly controHed by the FDA. 

Pesticides. Chlorinated hydrocarbon pesticides (qv) are often found in feed or water consumed by cows (19,20) subsequently, they may appear in the milk, where they are not permitted. Tests for pesticides are seldom carried out in the dairy plant, but are most often done in regulatory or private specialized laboratories. Examining milk for insecticide residues involves extraction of fat, because the insecticide is contained in the fat, partitioning with acetonitrile, cleanup (FlorisH [26686-77-1] column) and concentration, saponification if necessary, and determination by means of paper, thin-layer, microcoulometric gas, or electron capture gas chromatography (see Trace and residue analysis). 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

Law and Goerlitz in 1970 reported the effective removal of co-extractives from water using microcolumns of these three adsorbents for the analysis of chlorinated pesticides. The development of polystyrene resins such as XAD increased the ability to concentrate pesticide residues from water. Large volumes of sample water could be passed through an XAD resin and the pesticide would adsorb on the resin. Elution of the pesticide by an organic solvent such as methanol and subsequent cleanup by the adsorbent materials became the industry standard. 

Colorimetric methods (3, 6-10), some of which are specific, have been developed for the determination of DDT in small amounts. For benzene hexachloride (hexachloro-cyclohexane), chlordan, and toxaphene, however, specific analytical methods have not been developed, and their residues have been evaluated by the determination of organically bound chlorine. The procedure comprises extraction of the insecticide residue from the sample with benzene or other suitable organic solvent, evaporation of the solvent, treatment of the residue with isopropyl alcohol and metallic sodium, and finally determination by standard methods of the amount of chloride ion formed. 

Portions of the treated hay were extracted with benzene, and aliquots of the benzene solution were evaporated to dryness on the steam bath, with a gentle air current to remove the last traces of solvent. The residues were then taken up in deodorized kerosene and tested against houseflies by the turntable method. For comparison, extracts were made up to contain the same amounts of technical toxaphene as were indicated by the chlorine determinations to be present in the treated hay. 

Extracts of these fat samples were treated with sodium sulfate-concentrated sulfuric acid mixture and fuming acid by the method described by Schechter et al. 5) in order to separate the organic-chlorine compound from the fatty materials. An infrared spectrum from 7 to 15 microns on carbon disulfide solutions of the residues from the fat qualitatively identified the organic-chlorine compound as toxaphene. All the bands of toxaphene in this spectral region were plainly seen in the treated steer extract, whereas none of the absorption bands were visible in the untreated steer extract. 

Table II. Toxicity to Houseflies of Residues of Beef-Fat Extracts Containing Chlorinated...

The solvent extraction of chlorinated pesticide residues from soil is often achieved by using mixtures of solvents such as hexane-isopropanol or hexane acetone, but can be unsatisfactory owing to the emulsification problems [2, 3] or, with hexane-isopropanol, poor recovery [2, 4], Acetone extraction of soil is efficient [4, 5] but problems can arise from large amounts of coextracted material unless an efficient clean-up technique [6] is used prior to analysis by gas chromatography. 

TMBA-ICI4 (1.3 g, 3.1 mmol) is added to the acetanilide (3.1 mmol) in AcOH (30 ml) and the mixture is stirred for 24 h at room temperature. The precipitated TMBA-ICI2 is collected and the filtrate is evaporated under vacuum. The residue is washed with NaHSO, (5%, 10 ml), NaHCO, (5%, 15 ml) and extracted with CH.CI, (3 x 20 ml). The organic extracts are filtered through A120, and evaporated to yield the chlorinated acetanilide. 

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