Methylene chloride-soluble residues

Methylene chloride-soluble residues. Methylene chloride-or chloroform-soluble C-labeled products were major residues in all of the plant tissues examined except peanut cell ciiltures (Figure 3). Chloroform-soluble C accounted for 59.2 of the radioactivity isolated from peanut roots 48 hr after treatment with [ C]PCNB. The radioactivity was in the form of PCNB (28.7 ), pentachloroaniline (22.5 ), pentachlorothiophenol (2.6 ) pentachlorothloanlsole (3.1 ) pentachlorothloanlsole sulfoxide (0.5 ) S-(pentachlorophenyl)-2-thioaoetic acid [(S-(PCP)ThioAcetate] (0.5 ) and S-(pentachlorophenyl)-3-thio-2-hydroxypropionic acid [S-(PCP)ThioLactate] (0.2 ) and S-(PCP)Cys (trace) (J), The structures of these compounds are shown in Figure 13. Based on TLC, the last three compounds in this list were classified as polar chloroform- or methylene chloride-soluble residues and the remaining compounds were classified as nonpolar residues. 

Polar methylene chloride-soluble residues. Polar methylene chloride-soluble residues were found In most of the plant tissues treated with [ C]PCNB (Figure 14). These products were only Identified In peanut IT). The polar methylene chloride-soluble metabolites from peanut, S-(PCP)Cys, S-(PCP)ThloAcetate, and S-(PCP)ThloLactate, were probably produced from S-(PCP)GSH by the pathway shown In Figure 15. Intact peanut plants treated with S-[( C)PCP]Cys and harvested 20 days later yielded S-(( C)-PCP]ThloAcetate In T.3% yield however, S-(( C)PCP]ThloLactate was not detected. An S-substltuted 2-thloacetlc acid metabolite has also been reported In the metabolism of EPTC In the rat ( 1 ). 

Nonpolar methylene chloride-soluble residues. Pentachloro-thloanisole and pentachlorothioanlsole sulfoxide were present in the nonpolar methylene chloride-soluble fraction from each of the plant systems examined (Figure 14). In addition, pentachloro-thiophenol was detected in some of these extracts. Pentachloro-thioanisole has been reported as an important residue of PCNB in almost every biological system that has been examined for PCNB metabolism and pentachlorothlophenol has also been reported as a residue in several of these systems S). The formation of these residues from S-(PCP)GSH via the pathway shown in Figure 16 was considered highly probable. Recent vivo studies indicated that such a system also operates in mammals in the metabolism of propachlor ( ) and pentachlorothioanlsole (20). vitro... 

Ninety-eight grams of 6-chloro-2-chloromethyl-4-phenylquinazoline 3-oxide hydrochloride were introduced into 600 cc of ice cold 25% methanolic methylamine. The mixture was initially cooled to about 30°C and then stirred at room temperature. After 15 hours the reaction product which precipitated was filtered off. The mother liquor was concentrated in vacuo to dryness. The residue was dissolved in methylene chloride, washed with water and dried with sodium sulfate. The methylene chloride solution was concentrated in vacuo and the crystalline residue was boiled with a small amount of acetone to dissolve the more soluble impurities. The mixture was then cooled at 5°C for 10 hours and filtered. The crystalline product, 7-chloro-2-methylamino-5-phenyl-3H-1,4-benzodiazepine 4-oxide, was recrystallized from ethanol forming light yellow plates, MP 236° to 236.5°C. 

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. 

Figure 14. Methylene chloride- or chloroform-soluble residues were isolated from plant tissues treated with V C] PCNB. All tissues were treated for 3 days except lake water which is rich in blue green algae (9 h), peanut plants (2-day treatment/2-day post-treatment), and peanut cell cultures (1 day).

The resulting styrene/maleic acid copolymer is soluble in hot water, in contrast to the starting material the aqueous solution of the product gives a distinctly acid reaction. The disappearance of the anhydride moiety can be verified by IR or C-NMR spectroscopic methods.The IR spectra of polymers should be recorded from a film of the sample prepared on a KBr pellet (freshly made from KBr powder). For this, a drop of a solution of the polymer in a low-boiling solvent (e.g.,THF, methylene chloride) is placed on the pellet.The residual solvent can often be removed directly in the IR beam.The resulting spectra are characterized by their sharp bands. 

Although solvents may form two visibly distinct phases when mixed together, they are often somewhat soluble in each other and will, in fact, become mutually saturated when mixed with each other. Data on the solubility of various solvents in water (Table 2.2) and on the solubility of water in other solvents (Table 2.3) should be consulted when selecting an extraction solvent pair. For example, 1.6% of the solvent dichloromethane (or methylene chloride) is soluble in water. Conversely, water is 0.24% soluble in dichloromethane. According to Table 2.3, when the phases are separated for recovery of the extracted analyte, the organic solvent layer will contain water. Similarly, according to Table 2.2, after extraction the depleted aqueous phase will be saturated with organic solvent and may pose a disposal problem. (Author s note I previously recounted [43] my LLE experience with disposal of extracted aqueous samples that were cleaned of pesticide residues but saturated with diethyl ether. Diethyl ether is 6.89% soluble in water at 20° C.)... 

The analytical method developed in the BCR project (Franz and Rijk, 1997) to determine residual carbonyl chloride monomer in polymers was pre-validated by two laboratories and found appropriate for the quantitative determination of carbonyl chloride with a LOD = 0.3 mg/kg below and in the range of the restriction criterion of 1 mg/kg polymer, with observed repeatability values of r = 0.23 and 0.32 mg carbonyl chloride/kg polymer, respectively. The method is applicable to polycarbonate as well as to other polymers and copolymers where these are soluble in methylene chloride. 

That many chemical substances are not soluble in sc carbon dioxide permits selective extraction.100 It is often used with foods, for which it eliminates the possibility of leaving toxic residues of solvents such as methylene chloride. It also avoids the hydrolysis that might occur when esters (for flavors or fragrances) are recovered by steam distillation. It has been used to extract the flavor from hops, the caffeine from coffee, fat and cholesterol from foods,101 pecan oil,102 lavender oil (for which hydrolysis of linalyl acetate could occur in steam distillation), 103 ginseng (from which it does not extract pesticide residues),104 ginger,105 microalgae,106 cooked chicken,107 ethanol from cider,108 and many others. One method used with aromas and con-... 

Fraction 4 = residue soluble in methanol/methylene chloride (7 3). 

Fraction 1 = soluble in methylene chloride. Fraction 2 = residue soluble in methanol. 

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