Dichloromethane extraction, analysis

Figure 10.1 Analysis of racemic 2,5-dimethyl-4-hydroxy-3[2H]-furanone (1) obtained from a strawbeny tea, flavoured with the synthetic racemate of 1 (natural component), using an MDGC procedure (a) dichloromethane extract of the flavoured strawbeny tea, analysed on a Carbowax 20M pre-column (60 m, 0.32 mm i.d., 0.25 p.m film thickness earner gas H2, 1.95 bar 170 °C isothermal) (b) chirospecific analysis of (1) from the sti awbeny tea exti act, ti ansfened foi stereoanalysis by using a pemiethylated /3-cyclodextrin column (47 m X 0.23 mm i.d. canier gas H2, 1.70 bar 110 °C isothemial). Reprinted from Journal of High Resolution Chromatography, 13, A. Mosandl et al., Stereoisomeric flavor compounds. XLIV enantioselective analysis of some important flavor molecules , pp. 660-662, 1990, with permission from Wiley-VCH.

The analytical procedure for the alkaline aqueous layer containing n is as follows. After acidifying the solution (about pH 2) with 4 mL of concentrated HCl, extract twice with 100 mL of dichloromethane. Dry the dichloromethane extract with anhydrous sodium sulfate and collect the dried solution in a 300-mL round-bottom flask. Evaporate the solvent under reduced pressure. Dissolve the residue in a mixed solvent consisting of 4mL of ethyl acetate, 0.5 mL of methanol and 30 pL of concentrated HCl. To this mixture, add 7 mL of diazomethane-diethyl ether solution and allow the mixture to stand at room temperature for 1 h. Concentrate the reaction mixture to 0.5 mL under reduced pressure and evaporate the solvent in a gentle stream of nitrogen. Dissolve the residue in a small volume of dichloromethane-n-hexane (1 2, v/v) and transfer the solution to the top of column. Elute with solvent of the same composition, discard 60 mL of the initial eluate and collect 100 mL of the subsequent eluate in a 200-mL round-bottom flask. Concentrate the eluate to 0.5 mL under reduced pressure, evaporate the solvent in a gentle stream of nitrogen and dissolve the residue in an appropriate volume of acetone for analysis. 

Keith et al. [36] and Reijnders et al. [37] reviewed applications of gas chromatography-mass spectrometry to sediment analysis. Lopez-Avila et al. [38] investigated the efficiency of dichloromethane extraction procedures for the isolation of organic compounds from sediments prior to gas chromatography-mass spectrometry. The compounds investigated were the 51 priority pollutants listed by the Environmental Protection Agency, USA. 

Montmorillonite K-10 (1 g) was mixed thoroughly with Fe(NC>2)3 -9H20 (0.404 g, 1 mmol) using a pestle and mortar. This mixture was added to neat tetrahydro-pyranyl ether 1 (1 mmol) in a beaker and was placed into a microwave oven (900 W). The mixture was irradiated for the indicated time. After completion of the reaction, which was monitored by TLC or GC, the crude product was extracted with dichloromethane. GC analysis of the crude product showed that 2 were obtained in high to excellent yields. Final purification was achieved by column chromatography using hexane-ethyl acetate as eluent. 

Freon or dichloromethane extraction gives precise and accurate estimates of oil and grease contents of soil [104]. Thermal desorption mass spectrometry has been used as a rapid method for the determination of oil in soil. The analysis takes only 20 minutes [33]. 

In the third official proficiency test, at least four laboratories failed to find (l-methylethyl)phosphonic acid (IPPA, CAS 4721-37-3) most probably because the water extract was not prepared properly. These laboratories proceeded to neutral and alkaline dichloromethane extraction and some even evaporated the water to dryness. However, recovery of IPPA requires direct analysis of the water sample by LC/MS (or CE) or else cation exchange, evaporation of the sample to dryness, and derivatization (methy-lation) of the residue. 

Figure 7. Part of a TIC chromatogram obtained after the GC/MS analysis of rubber contaminated with diesel fuel and sulfur vesicants, (a) Dichloromethane extract and (b) thermodesorption at 120 °C. 1, mustard gas 2, mustard disulfide. Data recorded at TNO-PML on a VG 70-250S GC/MS instrument (Micromass, UK) (40). (Reproduced from Wils, E. R. J., Hulst, A. G., de Jong, A. L., J. Chromatogr., 625, 382-386 (1992) by permission of Elsevier Science)...

Finally the sludge is extracted with 2x25 ml dichloromethane (DCM-3). The dichloromethane-extracts are combined and spiked with 50 pg each of the following deuterated internal standards toluene-ds, naphthalene-dio biphenyl-dio, phenanthrene-dio, pyrene-dio, crysene-d and phenol-dg. The extract is dried with sodium sulphate, and concentrated to 5 ml at 30 C using a modified Kudema Danish destination. When necessary the volume is further reduced to 1,0 ml under a gentle stream of nitrogen at 30°C prior to GC-MS analysis. 

GLC analysis of a sample of the crude, aqueous solution indicates the presence of 95% of the theoretical amount of glyceraldehyde acetonide. This crude, aqueous solution can be used for further chemical transformations,2 but was not stored for more than 6 hr at 0°C. GLC analysis of the aqueous layer after dichloromethane extraction still indicates the presence of about 30% of the total amount of glyceraldehyde acetonide in the aqueous solution. 

EN Standard (1999b) Water quality - determination of parathion, parathion-methyl and some other organophosphorus compounds in water by dichloromethane extraction and gas chromatographic analysis. EN 12918 1999. 

The dichloromethane extract from Wilbrandia ebracteata (p.o.) significantly reduced the paw elevation time (1 mg/kg) and cell influx (10 mg/kg) in zymosan-induced arthritis in rats. The same extract inhibited COX-2 activity, as measured by PGE2 production, without affecting that of COX-1. Moreover, nitrite release was clearly and significantly reduced at a dose of 10 mg/kg (p.o.). The analysis of the pharmacological data, together with the HPLC analysis of the extracts, points to an anti-inflammatory effect based on an associated reduction in nitric oxide (NO) release and COX-2 inhibition by the cucurbitacins... 

EN 12918, Water Quality — Determination of Parathion, Parathion-Methyl and Some Other Organophosphorous Compounds in Water by Dichloromethane Extraction and Gas Chromatographic Analysis, October 1999. 

Mass spectrometry is today the method used most frequently for identification and structure elucidation of unknown compounds. GC/MS investigations have been used in the combination with thermal desorption as extraction procedure, for the analysis of the dichloromethane extract and for the derivatization products (Thurow et al., 1997). Investigations have been carried out with an HP 5973 MSD (Hewlett Packard Inc.) in combination with an cold injection system CIS 3 (Gerstel GmbH, Germany). 

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