Methylene chloride water cleaning

Acetic anhydride (7 ml) was added to a solution of 6.16 g of crude 2-aminomethyl-7-chloro-2,3-dihydro-5-(2-fluorophenyl)-lH-1,4-benzodiazepine in 200 ml of methylene chloride. The solution was added to 200 ml of saturated aqueous sodium bicarbonate and the mixture was stirred for 20 minutes. The organic layer was separated, washed with sodium bicarbonate, dried over sodium sulfate and evaporated to leave resinous 2-acetylaminomethyl-7-chloro-2,3-dihydro-5-(2-fluorophenyl)-IH -1,4-benzodiazepine. This material was heated with 40 g of polyphosphoric acid at 150°C for 10 minutes. The cooled reaction mixture was dissolved in water, made alkaline with ammonia and ice and extracted with methylene chloride. The extracts were dried and evaporated and the residue was chromatographed over 120 g of silica gel using 20% methanol in methylene chloride. The clean fractions were combined and evaporated to yield resinous 8-chloro-3a,4-dihydro-6-(2-fluorophenyl)-l- methyl-4H-imidazo[l,5-a][l,4] -benzodiazepine. 

Lee and Stokker [161] have developed a multi-residue procedure for the quantitative determination of 11 triazines in non saline waters by a gas chromatographic method using a nitrogen-phosphorus detector. Ametryne, Atraton, Atrazine, Cyanazine, Prometron, Prometryne, Propazine, Simazine, Simetone and Simetryne were used. All of them could be successfully quantified on both the Ultrabond 20m and 3% OV-1 columns. Extraction was by methylene chloride and clean-up on Florasil. Recoveries of triazines at 10, 1.0... 

Evaporate the sample to dryness with clean, dry nitrogen. Add 250 /jl of methanol and 50 fil of concentrated sulfuric acid. Heat at 60° for 45 min. Add 250 fil of distilled water and allow to cool. Then add 50 fil of chloroform or methylene chloride. Shake the mixture for 2 min. Remove the bottom layer with a syringe. Evaporate to dryness with clean, dry nitrogen. Acetylate with 50 ju.1 of three parts acetic anhydride and two parts pyridine for 30 min at 60°. Evaporate to dryness with clean, dry nitrogen. Dissolve the residue in 25 fi of ethyl acetate. 

Preparation of the acetate derivative Concentrate the aqueous mixture of saccharides to approximately 0.5 ml in a 20-50 ml container. Reduce the saccharides by adding 20 mg of sodium borohydride that has been dissolved carefully into 0.5 ml of water and let the reducing mixture stand at room temperature for at least 1 hour. Destroy the excess sodium borohydride by adding acetic acid until the gas evolution stops. Evaporate the solution to dryness with clean nitrogen. Add 10 ml of methanol and evaporate the solution to dryness. Acetylate with 0.5 ml (three parts acetic anhydride and two parts pyridine) overnight. Evaporate to a syrupy residue and add 1 ml of water. Evaporate again to dryness to remove the excess acetic anhydride. Dissolve the residue in 250 /d methylene chloride. 

One solution is to replace the column, but a less expensive approach is to attempt to clean the column. Baking is one approach that removes some forms of contamination, but also shortens the column life because it removes some of the stationary phase. A solvent rinse is the most effective means of cleaning a bonded or cross-linked phase column. Solvent rinse kits are available with instructions from most column manufacturers. The procedure involves forcing solvents through the GC column, usually in the following order—water, methanol, methylene chloride, and hexane—using 10-15 psi back pressure. 

Water samples are acidified and extracted with solvent (Kawamura and Kaplan 1983 Muir et al. 1981). Clean-up steps may be used (Kawamura and Kaplan 1983). Methylene chloride is often used as the extracting solvent, and it may interfere with the nitrogen-phosphorus detector. In this case, a solvent-exchange step is used (Muir et al. 1981). Analysis by GC/NPD or GC/MS provides specificity (Kawamura and Kaplan 1983 Muir et al. 1981). Accuracy is acceptable (>80%), but precision has not been reported. Detection limits were not reported, but are estimated to be 0.05-0.1 pg/L (Muir et al. 1981). Detection limits at the low ppt level (ng/L) were achieved by concentrating organophosphate esters on XAD-2 resin. The analytes were solvent extracted from the resin and analyzed by GC/NPD and GC/MS. Recovery was acceptable (>70%) and precision was good (<10% RSD) (LeBel et al. 1981). 

A method for sediment involves Soxhlet extraction followed by filtration, and concentration to 5 mL. The residue is diluted with water, acidified, extracted with methylene chloride, and then the extracts are dried and evaporated to dryness. The residue is cleaned up on an alumina column. Analysis is performed by GC/NPD. Good recovery (81-97%) and precision (>15% RSD) were reported detection limits were not reported (Muir et al. 1981). 

Waste water Extraction with methylene chloride clean-up by column chromatography i f requi red GC/FPD... 

Waste water Extraction with methylene chloride solvent removal optional clean-up using GPC and/or SPE columns Capillary GC/FPD confimation using second GC column... 

In the Trauzl test, the mixture produced an expansion of 24 cc./gram, which is indicative of a high energy reaction. Card gap tests were also positive the value at room temperature is approximately 25 cards. From these results it was concluded that a mixture of methylene chloride with nitrogen tetroxide constitutes a definite explosive hazard. This conclusion was not immediately apparent as a result of compatibility and impact testing alone. Methylene chloride was not recommended as a solvent for cleaning N2O4 systems instead, a water flush is used for this operation. 

Extraction of 1 L of water with 15% methylene chloride in hexane using a separatory funnel. Concentration using K-D. Clean up (if needed) by Florisil fractionation or acetonitrile partition. 

Waters, soils, sediments, sludges <30% solids Dilution to 1% solids and extraction with methylene chloride, concentration using K-D. Clean up using GPC and SPE. GC/FPD (Method 622) 3.8 ng/L 60-120 EPA 1992c... 

A comparative study was conducted by cleaning XAD-2 resin by ultrasonic and Soxhlet extraction procedures. Two batches of XAD-2 resins from the same lot of uncleaned resin were cleaned by backwashing with water and then were subsequently extracted with methanol, acetonitrile, and methylene chloride. The solvent-to-resin volume ratio for both methods was 5 1. The volumes of wet resin for the Soxhlet extraction and the ultrasonic bath were 100 mL and 50 mL, respectively. The ultrasonic cleaning procedure was done in a Teflon-lined screw-cap amber jar (250 mL) for 1 h in each solvent. The Soxhlet extraction sequence was 24 h in methanol, 24 h in acetonitrile, and 48 h in methylene chloride. 

Figure 4. Capillary GC profile of 200-mL resin sampling blanks of XAD-2 column with Milli-Q water (pH 2.3). An initial methylene chloride elution of the clean resin (XAD-2 blank) was followed by a 30-L run of distilled water (XAD-2, 30 L) and then an additional 45 L of distilled water (XAD-2, 45 L additional). (See text for sampling detail.) The third bed volume was concentrated to 1 mL, and 2.5 pL was injected into the GC. Y-axis 1 E0 = 0.067 ng/L tol E2 = 6.7 ng/L.

A resin to be cleaned was packed into a 3-L capacity addition funnel and washed first with two volumes of high-purity water. The MSC-1 resin was then washed sequentially with 2 bed volumes of 2.0 N HC1, 5 bed volumes of high-purity water, 2 bed volumes of 1.5 N NaOH, and 5 bed volumes of high-purity water these HC1, water, NaOH, and water washes were then repeated. The same procedure was carried out with A-162, except that the order of acid and base was reversed. The resins were then extracted for at least 16 h in methanol in a Soxhlet apparatus. The final cleanup steps for MSC-1 consisted of a sequential elution with 2 bed volumes of methanol, 1 bed volume of 1.0 N NH3 in 122 methanol/882 methylene chloride (made as described later), 2 bed volumes of 122 methanol/882 methylene chloride (solvent 1), and 3 bed volumes of methanol. The same steps were used with A-162 except that HC1 replaced NH3 in the second wash. The resins were considered to be clean at this point, and they were stored in methanol. 

Dieckmann et al. [537] assayed fenpropimorph fungicide and its main metabolite fenpropimorphic acid in soil using acetone-water extraction, partitioning with methylene chloride, gel permeation clean-up, methylation of the metabolite and gas chromatography with NP detection, and gas chromato-graphy-mass spectrometry. 

This is applied to separate acidic or basic organics from neutral organics. The solvent extract is shaken with water that is highly basic. The acidic organics partition into the aqueous layer whereas, the basic and neutral compounds stay in the organic solvent and separate out. After this, the aqueous layer is acidified to a pH below 2, and then extracted with methylene chloride. The organic layer now contains the acid fraction Phenols, chlorophenoxy acid, herbicides, and semivolatile organic pollutants are cleaned up by the procedure described above. 

Solid samples extracted with acetonitrile extract diluted with water the resulting solution mixed with methylene chloride-petroleum ether mixture (20 80) (A) and shaken analyte partitions into (A) solvent layer (A) repeatedly washed with saturated NaCl solution the extract then cleaned up on a florisil column (first eluted with 200 ml solution A and then with a mixture of methylene chloride 50% and 1.5% acetonitrile in petroleum ether eluant concentrated and diluted to desired volume with petroleum ether analyzed by GC-ECD (Pomer-antz et al., 1970). 

Most often, trip blank contamination originates in the laboratory, either from common airborne laboratory contaminants (methylene chloride, acetone) or from laboratory water containing VOCs, typically methylene chloride, acetone, and toluene or water disinfection byproducts (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform). Rare, but well documented sources of trip blank and associated field samples contamination are insufficiently clean sample... 

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 SPE assay was further modified by Cone et al. by combining the assay for heroin and its metabolites with cocaine and its metabolites into a single procedure. Hair wash and incubation fractions were added to a conditioned Clean Screen SPE cartridge. The cartridges were washed with deionized water, pH 4 acetate buffer, and acetonitrile. The cartridges were aspirated to dryness and the analytes were eluted with a solution of methylene chloride 2-propanol (80 20) with 2% ammonium hydroxide. The solvent extract was evaporated and derivatized. 

The extraction of aflatoxins (Fig. 5.9) from corn, peanuts, and peanut butter involves the dissolution of the aflatoxins in an aqueous methanol extract, followed by extraction with chloroform and clean-up on a silica-gel column. The extraction is carried out with 50 g of food material and 200 mL of methanol/water (85 15) for 30 min. Filter 40 mL of the extract and collect the filtrate. Add 40 mL of 10% sodium chloride to salt out the aflatoxin and extract with 2 X 25 mL of chloroform. Evaporate to dryness and redissolve with 3 mL of methylene chloride. Sample is ready for addition to the silica-gel column that contains 0.5 g of packing material. The mechanism of sorption involves hydrogen bonding between the oxygen atoms of the aflatoxin and the silica gel. Sorption is from methylene chloride and elution is carried out with chloroform/acetone (9 1). 

An example is endrin in soil (Fig. 7.7). This highly chlorinated insecticide is extracted by Soxhlet extraction with hexane from a soil that has been mixed one to one with sodium sulfate to remove water. The hexane extract is further dried over sodium sulfate and the hexane is added to a hexane-loaded silica or CN SPE sorbent that has been prepared with hexane. The endrin is sorbed to the silica or CN by normal-phase mechanisms and may be eluted with a solvent that will overcome the interaction, such as methylene chloride or ethyl acetate. The more polar interferences are sorbed to the silica or CN sorbent and are not eluted with endrin. Thus, the SPE column performs both trace enrichment and SPE clean-up. See Chapter 5 for more examples. 

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