Extraction using diethyl ether

Cimbura and Kofoed (50),mentioned earlier, used GLC to separate amphetamine and methamphetamine after acetylation with acetic anhydride in methanol. Derivatives were extracted using diethyl ether and chromatographed op columns of either 3% OV-17, OV-1, or SE-30. Column temperature was 160°C. They also reported the chromatographic determination of acetylated morphine on 3% SE-30, OV-1, or OV-17 at temperatures of 220°C. Cruickshank et al.(21) separated 21 amino acids as their trifluoroacetylated methyl esters. The column was 5% neopentyl glycol succinate on Gas Chrom P. Column temperatures were both isothermal and programmed 65°C for 20 min at 1.5°C/min then 2°C/min until 42.5 min then 4°C/min until 60 min then isothermal until about 75 min (see Figure 12.2). Chang et al. (19), used BSA/pyridine to form the TMS derivatives of levodopa, methyldopa, tyrosine. 

Direct extraction using diethyl ether and petroleum ether, chloroform, benzene, acidified methanol, or their mixtures as the most suitable organic solvents (26,27)... 

Extraction using diethyl ether has also been used in another traditional method to determine the level of preservatives in a sample. In this case, benzoic acid can be extracted from a product at low pH using diethyl ether. By adjusting the pH of the product, and hence the ionisation of the acids themselves, it is possible to quantify benzoic acid in a soft drink in the presence of saccharin. After extraction the benzoic acid can be assayed spectrophotometrically or by titration (Egan et al., 1990c). 

Diethyl ether is also frequently used to delipidate extracts which are subsequently analyzed by conventional methods [46,55,67,175]. It has been reported that extraction using diethyl ether allows the quantitative removal of monomers from acidified aqueous wood extracts, while dimeric proanthocyanidins remain in the aqueous phase [121]. Recovery studies of (-)-epicatechin and (+)-catechin in synthetic wine solutions only yielded 24 % and 46 %, respectively, of the added amounts. Procyanidin B2, however, could not be detected in the lipophilic layer. Analogous results... 

Aroma Composilion of Ffmijircek. Li quid-liquid extraction using diethyl ether resulted in an aroma extract which represented the characteristic note of the original product. tJiat t.e. is seasoning-like, spicy, hcrltaccou.s, and fenugreek-like. The representativeness of the samples before and after purification was checked by sensory evaluation. 

Cadmium in umbilical cord blood and placental tissue was determined for 31 samples collected at the Gynecology Maternity Ward in Kikinda Hospital, and 30 samples collected at the Gynecology Maternity Clinic in Novi Sad, in the period 1996-1997. The samples of hepatizated blood and placental tissue were broken down by nitrous acid using a wet process, the fats were extracted using diethyl ether, and the cadmium concentration was determined by atomic absorption spectrophotometry on a graphite furnace (Vather, 1982 Stoeppler, 1983 Beauty, 1988). 

Certain amount of sodium azide is dissolved in water, and then 95 % ethanol with bromoalkane is added. Later, the mixture is heated to 70-90 °C and reluxs until the colorless oily liquid is produced. After reaction, the product is washed using water, and extracted using diethyl ether. The extraction liquid is dried by MgS04. Diethyl ether is evaporated at normal pressure, and the colorless oily liquid product 1,3-diazidopropane is evaporated under reduced pressure and collected. The yield is 93.6 %. The processes of 1,3-diazidopropane preparations are in Fig. 6.1. 

Fig. 9.3 Gas chromatogram of extracted amniotic fluid obtained at 17 weeks gestation from a mother at risk for methylmalonic aciduria and carrying an affected foetus. Amniotic fluid was extracted using diethyl ether and the methylated extract was chromatographed on 10 per cent poly(pthylene glycol) 400 at 108 C. The methylmalonate peak (peak arrowed) has superimposed upon it a peak representing the upper limit of normal. (Redrawn with modifications from Gompertz et al., 1974)...

Fig. 14.5 Chromatogram of organic acids extracted using diethyl ether and ethyl acetate from the urine of a patient with suberylglycinuria and separated as their methyl derivatives (diazomethane) on 3 per cent SE-30 on Chromosorb W (DMCS, 80-100 mesh) using temperature programming from 80°C to 250°C at 6°C min Peak identifications are 1, 3-hydroxybutyrate 2, adipate 3, 3-methyladipate 4, pimelate (heptanedioate) 5, octenedioate 6, suberate (octanedioate) 7, hexanoylglycine plus 4-hydroxyphenylacetate 8, azeleate (nonanedioate) 9, decenedioate 10, sebacate (decanedioate) 11, hippurate 12, unknown, 13, suberylglycine. (Redrawn with modifications from Truscott et al., 1979)...

To a vigorously stirred suspension of 2 mol of lithium amide in 2 1 of liquid atimonia (see II, Exp. 11) was added in 15 min 1 mol of propargyl alcohol (commercial product, distilled in a partial vacuum before use). Subsequently, 1 mol of butyl bromide was added dropwise in 75 min. After an additional 1.5 h, stirring was stopped and the ammonia was allovied to evaporate. To the solid residue were added 500 ml of ice-water. After the solid mass had dissolved, six extractions with diethyl ether were performed. The (unwashed) combined extracts were dried over magnesium sulfate and then concentrated in a water-pump vacuum. Distillation of the residue through a 40-cm Vigreux column afforded 2-heptyn-l-ol, b.p. 

Epichlorhydrin (ECH) detection starts with detecting epoxide cycle using hydrochloric acid in combination with sodium chloride the reaction product - 1,3-dichlorhydrin - is extracted in diethyl ether and concentrated by removing the latter. Gas-liquid chromatography with a flame-ionization detector is used to detect glycerin 1,3-dichlorhydrin. The sensitivity of the method is 0.01 mg/dm. ... 

One can readily appreciate the usefulness of pK value in purification procedures, e.g. as when purifying acetic acid. If acetic acid is placed in aqueous solution and the pH adjusted to 7.76 [AcOH]/[AcO ] with a ratio of 0.1/99.9], and extracted with say diethyl ether, neutral impurities will be extracted into diethyl ether leaving almost all the acetic acid in the form of AcO in the aqueous solution. If then the pH of the solution is adjusted to 1.67 where the acid is almost all in the form AcOH, almost all of it will be extracted into diethyl ether. 

Aniline will be used as a second example. It has a pK of 4.60 at 25° in H2O. If it is placed in aqueous solution at pH 1.60 it will exist almost completely (99.9%) as the anilinium cation. This solution can then be extracted with solvents e.g. diethyl ether to remove neutral impurities. The pH of the solution is then adjusted to 7.60 whereby aniline will exist as the free base (99.9%) and can be extracted into diethyl ether in order to give purer aniline. 

The common impurities found in amines are nitro compounds (if prepared by reduction), the corresponding halides (if prepared from them) and the corresponding carbamate salts. Amines are dissolved in aqueous acid, the pH of the solution being at least three units below the pKg value of the base to ensure almost complete formation of the cation. They are extracted with diethyl ether to remove neutral impurities and to decompose the carbamate salts. The solution is then made strongly alkaline and the amines that separate are extracted into a suitable solvent (ether or toluene) or steam distilled. The latter process removes coloured impurities. Note that chloroform cannot be used as a solvent for primary amines because, in the presence of alkali, poisonous carbylamines (isocyanides) are formed. However, chloroform is a useful solvent for the extraction of heterocyclic bases. In this case it has the added advantage that while the extract is being freed from the chloroform most of the moisture is removed with the solvent. 

To which a solution of manganese sulfate (15 g), 3.1 g of chromium trioxide, 72 ml of water and 3.5 ml of sulfuric acid was added. After stirring for 3.5 hours at 3°C, extracted with diethyl ether. The organic layer was washed with water, dried over sodium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel using ethyl acetate-benzene (1 1) as eluent to give 2.35 g of the title compound. 

Extracting nitric acid using diethyl ether leads to explosive mixtures. 

IC-0 residue is cleaned up with a mixture of dichloromethane and acetone by liquid-liquid partitioning under neutral conditions and then extracted into diethyl ether under acidic conditions. The diethyl ether in the extract is removed by rotary evaporation and the residue is dissolved in buffer solution, which is subjected to a cleanup procedure using a Sep-Pak Cig Env. column. 

Byeon et al. [23] described a fluorimetric method for (z>)-penicillamine using 9-fluorenylmethyl pentafluorophenyl carbonate and acetonitrile. Capsules containing penicillamine were extracted with water and then filtered. The solution was incubated at 70 °C for 40 min with borate buffer solution. After cooling, the mixture was extracted with diethyl ether and the fluorescence of the aqueous phase measured at (excitation = 260 nm, emission = 313 nm). The calibration graph was linear for 0.4-5.0 pM of penicillamine with a coefficient of variation of 0.4%. 

Compound 51 was found to be unstable and difficult to purify, as described in the literature [93—95]. Therefore, 51 was not isolated, but was instead converted to the stable pinacol 1-acetamido-l-hexylboronate derivative 52. However, the acylated derivative 52 could not be purified by column chromatography as it was destroyed on silica gel and partially decomposed on alumina. Fortunately, we found that it dissolves in basic aqueous solution (pH > 11) and can then be extracted into diethyl ether when the pH of the aqueous layer is 5—6. Finally, pure 52 was obtained by repeated washing with weak acids and bases. It should be mentioned here that exposure to a strongly acidic solution, which also dissolves compound 51, results in its decomposition. Compared with other routes, the present two-step method involves mild reaction conditions (THF, ambient temperature) and a simple work-up procedure. It should prove very useful in providing an alternative access to a-aminoboronic esters, an important class of inhibitors of serine proteases. 

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